case study of keratoconus

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Fourteen years follow-up of a stable unilateral Keratoconus: unique case report of clinical, tomographical and biomechanical stability

• Alain Saad 1 , 2 ,
• Maria Rizk 1 &
• Damien Gatinel 1  

BMC Ophthalmology volume  22 , Article number:  245 ( 2022 ) Cite this article

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Keratoconus (KC) is a noninflammatory corneal ectatic disorder. In 2015, the Global Consensus on Keratoconus and Ectatic Diseases agreed that the pathophysiology of KC includes environmental, biomechanical, genetic, and biochemical disorders on one hand, and that true unilateral KC does not exist on the other hand. However, with the increasingly advancements in detection methods, we report the first case of a stable unilateral keratoconus with the longest follow up period of 14 years (2006–2020). We used topographic, tomographic, and biomechanical values for both eyes over the years to confirm the diagnosis, which has never been done before. Our study focuses on a single patient therefore it illustrates the mere possibility that unilateral keratoconus exists.

Case presentation

We present the case of a 19-year-old male with no previous ocular or general health conditions who presented to our clinic in November 2006 for incidental finding of decreased vision of the right eye (OD) on a routine examination. Topographies, tomographies, and biomechanical analysis of both eyes were obtained and showed a unilateral right keratoconus at the time. Patient admitted to unilateral right eye rubbing. Although we cannot prove that previous eye rubbing alone led to these initial symptoms, he was advised to stop rubbing and was followed up without any intervention for fourteen years during which topographic, tomographic, and biomechanical values for both eyes remained stable, proving for the first time that unilateral KC could exist.

We think that the data we are presenting is important because acknowledging that true unilateral keratoconus exists questions the genetic or primary biomechanical etiology of keratoconus versus the secondary biomechanical etiologies like eye rubbing. Our report also shows the importance of corneal biomechanics in detecting early changes. This is important to detect early, prevent progression, and tailor treatment.

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Keratoconus (KC) is a noninflammatory corneal ectatic disorder, characterized by steepening of the cornea associated with progressive stromal thinning and loss of best spectacle-corrected visual acuity. It is a relatively rare disorder and its prevalence varies from 0.002% to 0.3% depending on the studied population. In 2015, the Global Consensus on Keratoconus and Ectatic Diseases agreed that the pathophysiology of KC includes environmental, biomechanical, genetic, and biochemical disorders [ 1 ]. In 2016, Gatinel hypothesized that the biomechanical changes seen in KC cannot occur without chronic eye rubbing [ 2 ]. On the other hand, the global consensus also agreed that true unilateral KC does not exist [ 1 ]. In fact, KC is known to be a bilateral disease. However, even with the increasingly advanced detection methods, there are reports of true unilateral KC with a frequency ranging from 0.5% to 4%. In this case report, we report a case of stable unilateral keratoconus that has been followed for 14 years (2006–2020). Unilateral keratoconus has been described previously [ 3 4 ], but in our case, we incorporate topographical, tomographical, and biomechanical values on one hand, and long term follow up on the other hand, making this case report unique. The fellow eye in this patient had no identifiable clinical, tomographic and biomechanical abnormalities and remains normal and stable.

A 19-year-old previously healthy male presented to our clinic in November 2006 for incidental finding of decreased vision of the right eye (OD) on a routine examination. He had no prior ophthalmic or familial history. At the first visit, his best corrected visual acuity (BCVA) was 0.22 logMAR (-6.50 + 7.50 × 0) OD and 0 logMAR (-1.25 + 0.25 × 135) in the left eye (OS). The intraocular pressure was 14 mm Hg in both eyes (OU). Slit-lamp examination and fundoscopy were within normal limits OU. Corneal tomography (Orbscan, Baush and Lomb) OD showed a crab claw like appearance inferiorly with inferior decentration of the thinnest corneal point (456 μm) and a Kmax of 48.4 D (Fig.  1 -A). Corneal tomography OS, however, showed a perfectly regular cornea with a thinnest pachymetry of 531 μm, a centered thinnest point and a Kmax of 41.3 D (Fig.  2 -A). Patient admitted to unilateral right eye rubbing. He was counseled to avoid sleeping with pressure on his eyes and to strictly stop eye rubbing. Biomechanical analysis using Ocular Response Analyzer (ORA, Reichert) confirmed the presumptive diagnosis, showing keratoconic changes in the right eye and normal findings in the left eye (Fig.  3 -A).

A, B Topography (Orbscan) OD in 2006 ( A ) remaining unchanged in 2020 ( B ) showing keratoconic changes with an inferior steepening and thinning

A, B  Topography (Orbscan) OS in 2006 ( A ) remaining unchanged in 2020 ( B ) and showing within the normal topographic measurements

A, B  Ocular Response Analyzer (ORA) in 2014 ( A ) and in 2020 ( B ) showing stable biomechanical values over the years OU

The patient was diagnosed with a unilateral right keratoconus and was given eyeglasses to improve his right eye visual acuity as a first step. Artificial tears and anti-allergic eyedrops (Ketotifen 0.25 mg/ml) were also prescribed as permanent treatment. No further intervention was made at the time and the patient came back to clinic for annual follow ups over the years. During the 14 years of follow up we had with this patient, his refraction and visual acuity, as well as his topographies (Fig.  4 , A-B), tomographies (last Pentacam images OU showing keratoconic changes OD and normal anterior and posterior elevations OS in Figs.  5 and 6 ) and biomechanical properties remained stable OU (Figs.  1 -B, 2-B, 4-B). To further add evidence on normal posterior float of the left eye over the years, we have also included pictures of the Belin-Ambrosio enhanced ectasia report of both eyes that are strictly normal in the left eye (Fig.  7 A-B). Notably, biomechanical values on ORA including corneal hysteresis (CH) and corneal resistance factor (CRF) remained stable in both the keratoconic right eye and the normal left eye (Fig.  3 -B). Also, we proved stability of the left normal eye over time using the SCORE Analyzer software which showed no signs of early forme keratoconus in the left eye [ 5 ] (Fig.  8 A-B). Facing this stability over the years, no treatment was needed so far. We thus maintained our presumptive primary diagnosis of non-progressive true unilateral right keratoconus.

A, B  Differential maps OD ( A ) and OS ( B ) between 2006 and 2020

Pentacam of the right eye in 2020 showing an inferior cone with steep K values typical of keratoconus

Pentacam of the left eye in 2020 showing normal anterior and posterior elevations

A, B  Belin-Ambrosio enhanced ectasia report of both eyes showing keratoconus changes OD and normal anterior and posterior float values OS in 2020

A, B  SCORE Analyzer System in 2006 ( A ) and 2020 ( B ) showing no significant difference over time

The incidence of reported unilateral keratoconus varies depending on the methods used for diagnosis. Standard teaching is that keratoconus patients eventually develop bilateral disease if the patients are observed for a long enough period of time [ 6 ]. However, despite increasingly sensitive topographic, tomographic and biomechanical diagnostic methods, not all the fellow eyes of patients with unilateral keratoconus on diagnosis have identifiable abnormalities, even after long follow ups. Our case report is unique since it incorporates several imaging modalities during the follow up period of 14 years including corneal biomechanics which has never been reported before. It is thus the longest combination of topographic, tomographic and biomechanical follow up of a normal fellow eye in a unilateral keratoconus patient. Corneal biomechanics can predict early subtle corneal changes and thus can indicate early keratoconus. They are believed to be the first manifestation of keratoconus [ 6 7 8 ]. Having stable and within normal limits corneal biomechanics in the fellow normal eye of our patient reinforces the fact that mechanical trauma to the eye, such as rubbing, can induce ectasia on its own, as previously suggested by Gatinel [ 2 ]. Previously reported unilateral keratoconus cases either only included topographies as a non-clinical diagnosis, [ 3 4 ] or follow up time that was not long enough to confirm or infirm the hypothesis of unilateral keratoconus, or most importantly did not include secondary causes of keratoconus like eye rubbing in their inclusion criteria [ 4 ]. In fact, eye rubbing is an essential factor to consider, especially when dealing with true unilateral keratoconus as demonstrated in our patient. Not only does it indicate a risk factor we can act on to prevent progression, but it also means that primary biomechanical etiology has implications for understanding the pathophysiology of keratoconus. This case raises questions concerning the consensus statement in 2015 that true unilateral keratoconus does not exist.

This is important because acknowledging that true unilateral keratoconus may exist questions the genetic or primary biomechanical etiology of keratoconus versus the secondary biomechanical etiologies. The importance of corneal biomechanics plays a role in detecting early changes. This can have implications on understanding the pathophysiology of keratoconus to better tailor the treatment and predict the prognosis.

Availability of data and materials

All data generated or analyzed during this study are included in this published article [and its supplementary information files].

Abbreviations

• Keratoconus

Best corrected visual acuity

Ocular Response Analyzer

Corneal hysteresis

Corneal resistance factor

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Department of Ophthalmology, Rothschild Foundation Hospital, 25, Rue Manin, 75019, Paris, France

Alain Saad, Maria Rizk & Damien Gatinel

Department of Ophthalmology, American University of Beirut, Beirut, Lebanon

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DG is the main doctor of the patient, AS is the doctor who saw him over the years, MR witnessed the stability over time. All authors have read and approved the manuscript.

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Correspondence to Damien Gatinel .

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Saad, A., Rizk, M. & Gatinel, D. Fourteen years follow-up of a stable unilateral Keratoconus: unique case report of clinical, tomographical and biomechanical stability. BMC Ophthalmol 22 , 245 (2022). https://doi.org/10.1186/s12886-022-02412-z

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DOI : https://doi.org/10.1186/s12886-022-02412-z

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A Case-Control Study of Keratoconus Risk Factors

Moran, Sarah MD * ; Gomez, Ludovic MD * ; Zuber, Kevin MSc † ; Gatinel, Damien MD, PhD *

* Department of Anterior Segment & Refractive Surgery, Rothschild Foundation, Paris, France; and

† Department of Clinical Research, Rothschild Foundation, Paris, France.

Correspondence: Damien Gatinel, MD, PhD, Fondation Adolphe de Rothschild, 29 Rue Manin, Paris 75019, France (e-mail: [email protected] ).

The authors have no funding or conflicts of interest to disclose.

Purpose: 

To evaluate risk factors associated with keratoconus in a case-control setting.

Methods: 

This single center, prospective, case-control study was carried out from May 2014 to November 2017 at the Rothschild Foundation (Paris, France). Two hundred two patients with keratoconus and 355 control patients were investigated and followed by a single ophthalmologist. Data regarding multiple variables were gathered, including eye rubbing, pattern of eye rubbing, dominant hand, allergies, history of dry eye, screen time, sleep position, and night-time work.

Results: 

After multivariable analysis, the following variables showed significant results: eye rubbing with knuckles [odds ratio (OR) = 8.29; 95% confidence interval (CI): 3.92–18.26, P < 0.001] or fingertips (OR = 5.34; 95% CI: 2.44–12.21, P < 0.001), a history of dry eye (OR = 4.16; 95% CI: 2.3–7.7; P < 0.001), male sex (OR = 4.16; 95% CI: 1.47–11.89; P < 0.001), screen time (OR = 1.02; 95% CI: 1.01–1.04; P < 0.001), prone sleep position (OR = 11.63; 95% CI: 3.88–38.16), and side sleep position (OR = 10.17, 95% CI 3.84–33.73).

Conclusions: 

This study shows a strong correlation between eye rubbing and keratoconus, particularly when rubbing is performed with the knuckles. Additional associations were identified which may merit future investigation as risk factors, including sleep position, night-time work, and screen time.

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New dawn for keratoconus treatment: potential strategies for corneal stromal regeneration

• Shengqian Dou 1 , 2 ,
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Keratoconus is a progressive, ectatic and blinding disorder of the cornea, characterized by thinning of corneal stroma. As a highly prevalent among adolescents, keratoconus has been a leading indication for corneal transplantation worldwide. However, the severe shortage of donor corneas is a global issue, and the traditional corneal transplantation surgeries may superinduce multiple complications, necessitating efforts to develop more effective strategies for keratoconus treatment. In this review, we summarized several strategies to promote corneal stromal regeneration or improve corneal stromal thickness, including cell-based therapies, biosynthetic alternatives for inducing corneal regeneration, minimally invasive intrastromal implantation and bioengineered tissues for implantation. These strategies provided more accessible but safer alternatives from various perspectives for keratoconus treatment, paving the way for arresting the keratoconus progression in its earlier stage. For the treatments of corneal ectatic diseases beyond keratoconus, these approaches will provide important references and widen the therapy options in a donor tissue-independent manner.

Keratoconus is a progressive corneal ectatic disorder characterized by thinning of corneal stroma and asymmetrical conical protrusion of the cornea, which can lead to visual impairment or even blindness [ 1 , 2 , 3 ]. Keratoconus is one of the leading indications for corneal transplantation surgery worldwide [ 4 , 5 ], with an incidence of 1/2000 in the general population and even higher among young adults [ 2 , 6 ]. Keratoconus is the result of complex genetic and environmental interactions [ 7 , 8 , 9 ]. The most severe stage of keratoconus manifests with excessive ectasia, scarring and thinning stroma, which significantly impairs the vision, and the only option left for patients is corneal transplantation [ 1 ]. However, the severe shortage of the donor corneas available for transplant represents a global burden of blindness, with one cornea available for every 70 recipients in waiting [ 10 ]. Besides, traditional corneal transplantation surgeries can cause various complications, such as the severed corneal nerve plexus, dry eye, glaucoma and tissue rejection. Due to the immune rejection and chronic corneal allograft dysfunction, the poor long-term graft survival rate after keratoplasty usually brings a huge burden on patients. For these reasons, intense research effort has focused on corneal stromal regeneration to increase the corneal thickness of patients with keratoconus, and multiple therapy paradigms have been explored as alternative treatment modalities to preserve and improve the vision [ 11 , 12 , 13 , 14 ]. In this review, the strategies for corneal stromal regeneration are summarized, highlighting potential approaches for keratoconus treatment.

Strategies for corneal stromal regeneration

Cell therapy for keratoconus treatment.

Currently, corneal collagen cross-linking and corneal transplant remain the most preferred or even the only option for keratoconus treatment. However, neither of these approaches can fundamentally solve the underlying issue of the disease. Approximately 80–85% of the corneal thickness is composed of the corneal stroma, in which collagen fibrils and extracellular matrix are tightly arranged [ 15 , 16 ]. Keratocyte loss and excessive degradation of collagen fiber by matrix metalloproteinases are the culprit of keratoconus pathogenesis [ 17 , 18 ]. Hence, replacing or reviving the corneal stromal cells might be an ideal and direct approach; therefore, cell-based therapies for corneal stromal regeneration during keratoconus treatment have emerged and gained great concern.

To date, various ideas and choices for cell therapy of keratoconus were developed (Fig.  1 , Table 1 ). Keratocytes in the cornea are derived from neural crest cells. The number of keratocytes are limited in vivo, but they can be cultured in vitro and supplied as reliable cell source for intrastromal injection [ 19 , 20 ]. Besides, keratocyte progenitor cells, the committed stem cell populations that maintain capacity to self-renewal and differentiation, are thought to be a potential option for keratoconus treatment. The transplantation of healthy keratocyte progenitor cells into keratoconus corneas would provide a novel treatment modality that may slow the progression of keratoconus [ 21 ]. Moreover, the corneal stromal stem cells, a rare cell population resident in the peripheral cornea and limbus, can be isolated by specific surface markers from limbal stromal tissues [ 22 , 23 , 24 , 25 ]. Du et al. injected the human corneal stromal stem cells into mice corneas and did not observe elicit immune rejection over an extended period of time, suggesting an opportunity to develop cell-based therapies for corneal stromal diseases [ 26 ].

Cell sources used for keratoconus treatment. The figure was prepared by our group, and some of the elements in the diagram were provided by Figdraw ( http://www.figdraw.com )

However, several cell types mentioned above are still dependent on the corneal tissues, and the shortage of donor corneal tissues and the limited numbers of the particular cell populations is a significant challenge. The corneal stromal cells were found to have properties similar to other mesenchymal stem cells from various tissues [ 24 , 27 , 28 ], including adipose tissue [ 29 , 30 , 31 ], hematopoietic stem cells [ 32 ], dental pulp [ 33 , 34 ] and umbilical cord blood [ 35 ], which have been demonstrated to be used for keratoconus cell therapy [ 11 ]. For example, implantation of autologous adipose tissue-derived stem cells (ADSCs) into corneal stroma has been successfully tested for the treatment of keratoconus [ 30 , 31 , 36 , 37 ]. In addition, embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) also provide sufficient cell sources that could be differentiated to keratocytes required for keratoconus therapy [ 38 ].

Biosynthetic alternatives for inducing corneal regeneration

Replacement of the damaged tissue with corneal transplants is widely accepted treatment for corneal blindness. Over ten years ago, Per Fagerholm et al. developed a kind of recombinant human collagen type III (RHCIII), which has undergone synthesized in yeast, chemically cross-linked, and molded into a biosynthetic cornea mimic [ 39 ]. They conducted a phase 1 clinical study in which the biosynthetic cornea mimics were implanted to replace the distorted corneas of 10 patients with keratoconus or central scar. Strikingly, corneal re-epithelialization occurred in all patients, and nerve regeneration and touch sensitivity were also restored, demonstrating the property of the biosynthetic mimics in facilitating endogenous tissue regeneration. After then, further optimization of the biosynthetic corneal implants was done [ 40 , 41 ]. More significantly, Christopher D. McTiernan et al. developed a regeneration-stimulating liquid corneal replacement in a syringe that gels in situ, LiQD cornea, that comprises short collagen-like peptides, polyethylene glycol and fibrinogen [ 42 ]. The self-assembling synthetic collagen analog, as a low-cost and immune-compatible alternative, offering a safe and effective option to help address the current donor cornea shortage. Detailed information of these approaches is listed in Table 1 .

Mechanical methods to improve corneal stomal thickness

• Minimally invasive intrastromal implantation

Beside the strategy of corneal stromal cell replacement, restoring the physical properties of the corneal stroma cannot be ignored during keratoconus treatment [ 14 ]. Substantial biomechanical imbalance and weakening of the cornea can distinctly deteriorate the ocular surface homeostasis [ 43 , 44 ]. As we know, eye-rubbing is one of the major risk factors for keratoconus progressive, which can induce distinct alterations in corneal biomechanics [ 45 , 46 , 47 ]. And mechanical stretch was a trigger for keratoconus development and biomechanics-enzymes axis played a pathogenic role in keratoconus, as identified in our study [ 48 ]. Therefore, strengthening the biomechanical properties of the cornea should be considered during keratoconus treatment.

In recent years, corneal collagen cross-linking therapy, as a primary operative correction for progressive keratoconus, are used routinely to increase the biomechanical stability of the cornea. However, for keratoconus that has progressed to the most severe stage, corneal transplantation is the only option [ 1 ] (Table 2 ). Penetrating keratoplasty (PK) is a transplant procedure with full-thickness resection of the cornea, followed by grafting it with a full-thickness donor cornea, which was the treatment of choice for keratoconus until the late twentieth century [ 49 , 50 , 51 ]. When indicated, refinements in surgical approaches, like the deep anterior lamellar keratoplasty (DALK) [ 49 , 50 , 51 ] and anterior lamellar keratoplasty (ALK) [ 52 ], that were surgical procedures for removing part of the cornea. For instance, DALK involves replacement of the pathological corneal stroma down to the Descemet’s membrane but with the functional corneal endothelium retained, offers an effective alternative procedure that may lessen the risks including graft rejection and irregular astigmatism in PK. Despite DALK's success in restoring keratoconus patients' vision, there is still room for improvement regarding the operational complexity, restoring the physical properties of corneal stroma, preservation of the anterior corneal structure and nerve plexus, and suture-related complications. Therefore, suture-free implementation with smaller access cuts may be a preferred surgical option to arrest the progress of keratoconus, such as epikeratophakia (EP) [ 53 , 54 ], Bowman layer (BL) transplantation [ 55 , 56 ] and allogenic lenticule implantation [ 57 , 58 , 59 , 60 ]. Besides, our group have introduced a new effective procedure for the treatment of advanced keratoconus, named “femtosecond laser-assisted minimally invasive lamellar keratoplasty” (FL-MILK), in which partial thickness corneal stroma (stromal button) was implanted to the allogeneic corneal stroma through a small incision created by femtosecond laser (intrastromal pocket) [ 61 ] (as illustrated schematically in Fig.  2 ). Our study also indicated that FL-MILK can stabilize progressive KC in mild-to-moderate cases and advanced cases at 24-month follow-up with sustainable flattening effect of the anterior cornea curvature [ 62 ]. Indeed, while improving the stromal thickness, this minimally invasive surgical methods can maximally maintain the structural integrity and physical properties of the cornea, providing a feasible option for keratoconus treatment that should be put on the agenda.

Minimally invasive surgical methods and bioengineered grafts for keratoconus treatment. An intrastromal pocket with a small incision were created by femtosecond laser, the human stromal button ( a ) or bioengineered BPCDX graft ( b ) were gently inserted into the intrastromal pocket to increase the corneal thickness. The figure was prepared by our group

Bioengineered corneal tissues for implantation

For the keratoplasty to treat keratoconus, several materials can be used as biomedical implants. The natural cornea has particular advantage in mechanical properties and structures, while the severe shortage of donor corneas presents a global concern. Hence, intense research efforts have focused on effective alternatives to conventional corneal grafts. May Grifith et al . successfully multilayered corneal equivalents constructed from immortalized cell lines [ 63 ]. Per Fagerholm et al . conducted a phase 1 clinical study in which biosynthetic mimics of corneal extracellular matrix were implanted to induce corneal regeneration [ 39 ]. Our group have developed a protective decellularization strategy for the preparation of decellularized porcine cornea (DPC), which achieved equivalent levels in numerous properties compared with that of human cornea grafts [ 64 ]. All these studies offered prospects for visual rehabilitation of corneal blindness. Even more to the point, Mehrdad Rafat and colleagues have described a cell-free engineered corneal tissue, which was derived from purified type I porcine collagen with dual chemical and photochemical cross-linking applied, termed the bioengineered porcine construct, double cross-linked (BPCDX) [ 65 ] (Fig.  2 ). The authors extracted and purified collagen from a by-product of the food industry, the porcine skin, providing an abundant yet sustainable and cost-effective supply of raw materials for implants. At the same time, likewise, the authors insert the implant within the corneal stroma through a minimally invasive procedure. Notably, after 2 years of follow-up, no adverse event was reported, all participants' vision improved to the same degree as with a standard donor tissue transplant. The strategy proposed by this work in which accessible bioengineered corneal tissues and minimally invasive surgical methods were elaborately combined, would be an attractive option for treatment of advanced keratoconus, especially in resource-limited settings. Details of the approaches mentioned in this part are listed in Table 2 .

In this review, we summarized several approaches to promote corneal stromal regeneration or improve corneal stromal thickness, including cell-based therapies, biosynthetic alternatives for inducing corneal regeneration, minimally invasive intrastromal implantation and bioengineered tissues for implantation. Among these, a series of mechanical methods to improve corneal stomal thickness have been applied in clinical treatment of keratoconus. For instance, historically, PK has been the gold standard approach for the surgical treatment of advanced keratoconus with its good visual outcomes [ 50 , 51 ]. However, DALK is increasingly becoming the preferred primary surgical option in contemporary practice owing to its reduced rejection and astigmatism in PK complications. But the complexity of operation and risks of suture-related complications in DALK complications cannot be ignored, which prompted the occurrence of minimally invasive surgical methods [ 49 , 50 , 51 ]. For example, FL-MILK can maximally maintain the structural integrity and physical properties of the cornea while improving the stromal thickness, and its more precise and quick recovery might make it an effective alternative for the treatment of advanced keratoconus [ 61 ]. Besides, combined more accessible bioengineered corneal tissues and minimally invasive methods would be an attractive option for keratoconus treatment. Indeed, longer follow-up period and more cases are needed for several new improving approaches.

In addition, the severe shortage of donor tissue impeded the treatment of keratoconus through corneal transplant surgery, especially in resource-limited settings. Therefore, explorations in developing strategies to promote corneal stromal regeneration has never stopped. The ideal cell-based therapy is expected to replace or revive the diseased keratocyte cells by inducing regeneration or by exogenous transplantation of keratocyte-committed cells. Here we listed the cell sources, stage of research, advantages and limitations for various cell-based therapeutic methods. Among these, implantation of autologous ADSCs into corneal stroma has been successfully tested for the treatment of keratoconus in clinical trials [ 30 , 31 , 36 , 37 ], with its abundant and easily accessible cell source. Besides, biosynthetic alternatives for inducing corneal regeneration, including RHCIII [ 39 ] and LiQD cornea [ 42 ], providing low-cost and immune-compatible alternatives to help address the donor cornea shortage.

Conclusions

Collectively, this review highlighted the advances in therapeutic strategies that can promote corneal stromal regeneration or improve corneal stromal thickness for keratoconus treatment, providing important reference and foundations for developing potential interventions. These approaches have brought hopes for keratoconus therapy with more safe and accessible alternative options, reducing the surgical complication and burden of limited donor corneas globally. Generally, DALK has become an alternative to PK, while minimally invasive surgery will become a major trend in the future treatment of keratoconus. And keratocyte regeneration therapies will also usher in a new era, especially for the ADSCs-based treatment, though the potential of several novel therapies for achieving effective stromal regeneration need further explorations. Certainly, further studies should be conducted to confirm the optimal therapeutic methods and conditions for keratoconus intervention, and novel approaches would be developed to control and arrest the progression of keratoconus in its much earlier stage, which might hopefully postpone or prevent an invasive corneal surgery. For keratoconus treatment, the light is shining brighter on its way.

Availability of data and materials

All datasets used in this study are available from the corresponding author on reasonable request.

Abbreviations

Adipose tissue-derived stem cells

Embryonic stem cells

Induced pluripotent stem cells

Penetrating keratoplasty

Deep anterior lamellar keratoplasty

Anterior lamellar keratoplasty

Epikeratophakia

Bowman layer

Femtosecond laser-assisted minimally invasive lamellar keratoplasty

Bioengineered porcine construct, double cross-linked

Recombinant human collagen type III

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Acknowledgements

We thank Tong Liu for constructive suggestions on this review. Some of the elements in the diagram were provided by Figdraw ( http://www.figdraw.com )

This work was supported by the National Natural Science Foundation of China (82070923, 82101092, 82371032), Taishan Scholar Program (201812150, 202306390), Major Basic Research Project of Natural Science Foundation of Shandong Province (ZR2023ZD60) and the Academic Promotion Program and Innovation Project of Shandong First Medical University (2019RC009).

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Dou, S., Liu, X., Shi, W. et al. New dawn for keratoconus treatment: potential strategies for corneal stromal regeneration. Stem Cell Res Ther 14 , 317 (2023). https://doi.org/10.1186/s13287-023-03548-5

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• Review Article
• Published: 08 July 2020

Current perspectives in the management of keratoconus with contact lenses

• Li Lim   ORCID: orcid.org/0000-0003-1144-5737 1 , 2 , 3 &
• Elizabeth Wen Ling Lim 4  

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• Rehabilitation

Our aim is to review current and significant articles on contact lens wear in keratoconus patients. A comprehensive literature search of PubMed was performed for the following topics on contact lens wear in keratoconus patients: (1) characteristics of contact lens wearers, (2) safety and efficacy, (3) complications, (4) fitting techniques, (5) contact lens wear after procedures/surgeries, (6) patient satisfaction. A total of 104 studies were finally selected and reviewed. Gas permeable (GP) lens wear provided significantly better vision than glasses. Special cone design lenses had better patient comfort levels though there was no difference in best corrected visual acuity among the GP lenses. Soft lenses showed good efficacy for the treatment of mild-to-moderate keratoconus with newer designs improving visual performance such as customised hydrogel and novel pinhole lenses. Scleral and hybrid lenses provide good visual acuity and comfort for keratoconic patients previously intolerant to RGP lenses. RGP lens wear post-cross linking (CXL) is relatively well-tolerated. Contact lenses may still be required post intrastromal corneal ring procedures and post keratoplasty. Scheimpflug imaging and anterior segment optical coherent tomography (ASOCT) are useful in contact lens fitting. Computerized contact lens fitting techniques could reduce the chair time of lens fitting as well as improve comfort and visual performance. Contact lenses play an important role in the visual rehabilitation of keratoconus patients. New contact lens designs and materials have significantly expanded the available fitting options for keratoconus patients. Imaging technology can be utilized to guide contact lens fitting.

当前关于接触镜治疗圆锥角膜的观点

本文旨在对圆锥角膜患者佩戴角膜接触镜的重要文献进行回顾。我们于PubMed进行了全面的文献检索, 聚焦于圆锥角膜患者佩戴接触镜的问题: (1) 接触镜佩戴者的特点 (2) 安全性和有效性 (3) 并发症 (4) 适配技术 (5) 手术后的接触镜的佩戴 (6) 患者满意度。文中最终纳入并回顾了104项研究。

佩戴透气性 (Gas permeable, GP) 镜片比眼镜具有更好的视野。特殊设计的锥形镜片使病人拥有更佳的舒适度, 尽管最佳矫正视力与GP镜片之间并没有差异。软性镜片在治疗轻中度圆锥角膜方面显示出良好疗效, 新设计的如定制水凝胶和新型针孔镜片改善了视觉性能。巩膜和混合镜片为不能耐受RGP镜片的圆锥角膜患者提供了良好的视力和舒适度。佩戴RGP镜片后交联 (post-cross linking, CXL) 相对耐受性较好。角膜基质环术和角膜成形术后仍需佩戴接触镜。

Scheimpflug成像和眼前节光学相干断层扫描 (anterior segment optical coherent tomography, ASOCT) 有助于接触镜的适配。计算机化的接触镜适配技术可以减少镜片配戴的占用时间, 提高舒适度和视觉性能。

角膜接触镜在圆锥角膜患者的视觉康复中起着重要作用。新接触镜的设计和材料极大地扩展了圆锥角膜患者可用的适配选择。成像技术的利用有助于指导接触镜的配戴。

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Introduction.

Keratoconus is a progressive noninflammatory ectatic disorder of the cornea characterized by thinning and protrusion of the cornea leading to irregular astigmatism, myopia and poor vision [ 1 ]. It is the most common corneal ectatic condition with a prevalence of about 54 per 100,000 people in the United States [ 2 ]. A more recent nation-wide study performed in the Netherlands showed that the estimated prevalence of keratoconus in the general population is 1:375 (265 cases per 100,000, 95% CI: 260–270) which are five to ten times higher than previously reported values in population studies [ 3 ]. The mean age at diagnosis is 28.3 years with 60.6% of patients being male [ 3 ]. Risk factors include both genetic and environmental factors such as eye rubbing, personal history of atopy, and family history of keratoconus [ 4 ]. Due to its chronic and debilitating nature, keratoconus has a significant impact on vision-related quality of life (VRQoL) [ 5 ]. Hence the management of keratoconus patients involves long term care with the need for nonsurgical and surgical management options.

The corneal ectasia preferred practice pattern by the American Academy of Ophthalmology contains useful clinical guidelines for the overall management (nonsurgical and surgical) of keratoconus [ 6 ]. In the early stages of keratoconus, the vision could be corrected with glasses. However, in the moderate to advanced stages, spectacles play a limited role and contact lenses may be required for vision correction [ 7 ]. The global consensus on keratoconus and ectatic diseases recognized the importance of contact lenses in the visual rehabilitation of these patients. They recommend that rigid contact lenses be used in cases of unsatisfactory vision with glasses or conventional soft contact lenses (SCLs). In a patient who has failed a trial of corneal gas permeable (GP) lenses, the alternative contact lens options include hybrid (rigid center, soft skirt), toric, bitoric, keratoconus design SCLs, keratoconus design corneal GP contact lenses, piggy-back, corneoscleral, miniscleral, and scleral lenses [ 8 ].

The recent U.S. Food and Drug Administration approval of corneal cross-lining (CXL) provides an option that may slow or halt the progression of keratoconus. In recent years, there have been advances in the surgical management of keratoconus with surgical procedures such as CXL, topography guided excimer laser treatment combined with CXL, intrastromal corneal ring procedures performed alone or in combination with CXL, intraocular contact lenses performed alone or in combination with CXL, and anterior lamellar keratoplasty procedures. While these procedures have resulted in better visual outcomes, contact lens wear may still be required in postoperative visual rehabilitation.

With recent developments in contact lens properties and design, a greater range of contact lens options are available for patients with corneal irregularities. These options include larger diameter GP lenses, scleral lenses, hybrid lenses, and custom soft lenses. The ultimate aim is to optimise visual outcomes, patient satisfaction, and comfort for keratoconus patients using contact lenses. The benefits of new and more comfortable contact lens designs, combined with CXL’s effect on progression, should continue to reduce the number of individuals needing some form of keratoplasty procedure.

The purpose of this paper is to provide a review of current and significant articles focusing on the safety and efficacy of contact lenses in the visual rehabilitation of keratoconus.

A comprehensive literature search of PubMed, an electronic database, was performed up to 17th February 2019. The keywords used were: “contact lens”, “rigid contact lens”, “rigid gas permeable”, “RGP”, “Rose K contact lens”, “soft contact lens”, “scleral contact lens”, “miniscleral contact lens”, “piggyback contact lens”, “prosthetic contact lens”, “PROSE”, “hybrid contact lens”, “eye print pro”, “keratoconus”, “KC”, “corneal ectasia”, “ectasia”, “Scheimpflug”, “anterior segment optical coherence tomography”, and “ASOCT”. Using this method, 699 search results were generated. The references of retrieved articles were also searched for other relevant articles. Publications in English on the following topics on contact lens wear in keratoconus patients were included in our review: (1) characteristics and survey of contact lens wearers, (2) safety and efficacy, (3) complications, (4) fitting techniques, (5) contact lens wear after cross-linking, intracorneal ring segment insertion or penetrating keratoplasty (PK), (6) satisfaction and quality of life. Publications which did not contain information of interest were excluded. A total of 104 studies were finally selected and reviewed. In this paper, GP lenses refer to corneal GP lenses (older term RGP lenses).

Results and discussion

Characteristics and survey of contact lens wear in keratoconus patients.

Cohort and cross-sectional studies show that the majority of keratoconus patients wearing contact lenses are fitted with corneal GP lenses. (Table 1 ). All the different types of contact lenses mentioned in this paper have been tabulated for easy reference (Table  2 ).

Long-term studies (Collaborative Longitudinal Evaluation of Keratoconus (CLEK) and the Dundee University Scottish Keratoconus Study (DUSKS)) show that most patients are fitted with contact lenses when vision can no longer be corrected to at least 20/30 with glasses [ 9 , 10 ]. Longitudinal and cross-sectional studies worldwide on the characteristics and survey of contact lens wear in keratoconus patients show that GP lenses remain the mainstay treatment for keratoconus [ 11 , 12 , 13 , 14 , 15 , 16 ], with the majority of keratoconus patients attaining good visual acuity (VA) with lens wear. In the (CLEK) study looking at patients with moderate to severe keratoconus (95% had steep keratometry of >45 D), 74% of patients wore contact lenses, 16.1% wore spectacles, and 3.6% had no vision correction [ 11 , 16 ]. The CLEK population had good visual outcomes with 78% of patients achieving a best corrected visual acuity (BCVA) of 20/40 (6/12) or better in both eyes. 65% of patients wore GPs in both eyes and most of them (73%) reported that their lenses were comfortable. Most GP lenses (88%) were fitted with apical touch [ 11 , 16 ]. In the DUSKS study, contact lens wear was the mainstay of treatment (76% of 200 patients wore contact lenses) with 91% wearing GP lenses, 6% wearing hybrid contact lenses, and 2% wearing scleral lenses [ 9 ]. In another longitudinal study, due to good visual outcomes, contact lens wear delayed the need for surgery in keratoconus patients in 98.9% of eyes [ 17 ].

In a study on 130 keratoconus patients (228 eyes) in the United Kingdom, GP lenses of the spherical, elliptical and special cone lens design were used in 96.1% of eyes [ 12 ]. With contact lens wear, 87% achieved a VA of 6/9 (20/30) or better and 65% were able to wear their lenses for more than 12 h a day [ 12 ]. Another cross-sectional study in New Delhi showed similar findings with 99.9% of eyes wearing GP lenses (79.5% conventional GP, 20.4% Rose K) and 91% of eyes achieving a VA of 6/9 (20/30) or better [ 13 ]. Conventional GP lenses refer to non specialty design GP lenses. In Israel, similar results were also found in a cross-sectional study which reported that 78.7% of patients wore contact lenses (67.7% RGP, 13% soft CL, 4.2% scleral) and 21.3% of patients had undergone corneal graft surgery [ 14 ]. In Singapore, 67% of keratoconus patients wore contact lenses with 94% of them wearing GP lenses [ 15 ]. With contact lens wear, 83.3% of keratoconus eyes and 100% of keratoconus suspect eyes achieved a VA of 0.3 (decimal) (20/40). In the United Kingdom, Pullum et al. studied the characteristics of 538 patients with scleral contact lens wear over a 5-year period and found that primary corneal ectasia accounted for 61.4% of eyes [ 18 ].

Recent advances in surgical options for keratoconus include cross-linking, intracorneal rings, photorefractive keratometry, phakic intraocular lenses, and anterior lamellar keratoplasty. Although it would be important to compare the results of surgery and contact lens wear for a similar disease stage, there is currently no published literature on this subject.

Contact lens efficacy and comfort

Comparative studies—gp and soft/scleral/hybrid lenses.

Comparative studies show that specialty design contact lenses, new design scleral lenses and hybrid lenses had better patient comfort levels than conventional GP lenses (Fig.  1 , Table 3 ).

a Left eye Pentacam tomography: central conical pattern shown on the keratometry map. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Left eye: maximum keratometry 57.4 D; minimum keratometry 53.6 D; Rose K2 GP lens 6.30 mm BC/−8.25 D/8.7 mm Dia.).

Many comparative studies compared the efficacy and comfort of GP lenses with other lens types or glasses. Among GP lens types, Rose K had better patient comfort levels [ 19 , 20 ]. Most studies reported that GP lens wear provided significantly better vision and improved three-dimensional depth perception as compared with glasses though there was no difference in best contact lens corrected visual acuity (BCLCVA) among the GP lenses (Boston Equalens II, Boston 7, CFKE, Rose K, and Rose K2) [ 20 , 21 ]. There was also no difference in BCLCVA between Rose K and Kerasoft IC contact lenses for the treatment of mild-to-moderate keratoconus [ 22 ]. The study by Betts et al. reported no improvement in the VA in keratoconic patients wearing Rose K as compared with habitual lenses, though comfort levels were significantly higher, with 72% of patients stating that they preferred Rose K lenses over their habitual lenses and 87% reporting that they would continue wearing Rose K lenses [ 23 ].

A new randomized controlled study by Levit et al. compared the efficacy and comfort of Rose K and Zenlens (a Scleral lens manufactured in Boston XO2 material, Alden Optical/Bausch and Lomb, Kingston-upon-Thames, UK) [ 24 ]. It found no significant difference in VA ( P  = 0.563) or contrast sensitivity ( P  = 0.316). However, scleral lens wearers had higher subjective comfort scores ( P  = 0.002) [ 24 ].

When comparing GP/habitual lenses to hybrid lenses, visual outcome is equivocal with two studies showing that ClearKone (SynergEyes) hybrid lens wear had improved VA as compared with GP/habitual lens [ 25 , 26 ] while Hashemi et al. did not find a significant difference between these two lenses [ 27 ]. Contrast sensitivity was shown to be better in ClearKone lens wearers as compared with GP lenses [ 26 ]. Patient satisfaction and VRQoL were better in those who used ClearKone lenses [ 26 , 27 ]. Between hybrid lenses, the ClearKone lens has a better oxygen permeability at the central cornea, 2.0 mm and 4.5 mm temporal to the central cornea as compared with the SoftPerm lens as the soft lens material in ClearKone is silicone hydrogel (SiHy) compared with hydrogel material in the SoftPerm lenses [ 28 ]. SoftPerm lenses have since been discontinued in 2010 due to oxygen permeability issues.

In summary, the comparative studies show that newer specialty design keratoconus GP lenses had better comfort levels than conventional or habitual GP lenses although there was no difference in the BCVA between the two groups. For mild-to-moderate keratoconus, soft keratoconus design lenses (Kerasoft IC) attained similar BCLVA to Rose K lenses with better comfort levels achieved. The new hybrid lens (ClearKone) had better patient satisfaction and VRQoL  than GP/habitual lenses. A new scleral lens design (Zenlens) was more comfortable than Rose K lens.

Non-comparative studies—soft lenses

Studies show that soft lenses are able to provide satisfactory vision in mild-to-moderate keratoconus (Table 4 ). Newly designed soft lenses, customized hydrogel lenses and pinhole contact lenses widen the scope of vision correction of keratoconus with soft lenses.

Three non-comparative case series performed on soft lenses show good efficacy for the treatment of mild-to-moderate keratoconus. Sultan et al. showed that Toris K SiHy soft lenses are an effective alternative to GP lenses for the treatment of all grades of keratoconus (Amsler–Krumeich classification grades 1–4; mean keratometry 49.42 D), with no significant difference in BCVA with the two lenses [ 29 ]. The Toris K lenses are newly designed SiHy lenses with a toric front surface that is able to improve visual performance. Customised hydrogel contact lenses which incorporate vertical coma correction have also been found to improve both monocular and binocular visual performance in patients with mild-to-moderate keratoconus [ 30 ]. Higher order aberrations in patients with keratoconus can also be eliminated by wearing a novel pinhole soft lens (Purecon, New Delhi: 2.5 mm clear pupil, 8.3 mm base curve, 11.9 mm iris diameter, and 13 mm overall diameter) [ 31 ]. The pinhole effect is able to correct the aberropia caused by higher order aberrations such as vertical coma in patients with keratoconus.

Non-comparative studies—GP lenses

Case studies performed on GP lenses show that they are effective for the treatment of keratoconus and lens wear is comfortable (Table  4 ). The type of GP lens most frequently used depends on the severity of keratoconus, with monocurve GP lenses most frequently fitted in patients with mild-to-moderate keratoconus while bicurve GP lenses more frequently fitted in patients with severe and advanced keratoconus [ 32 ]. Two types of GP lenses (Menicon Z and YK) have comparable efficacy and comfort. YK lenses (Lucid Co, Seoul, Korea) are proprietary multicurve GP lenses for keratoconus. Menicon Z GP lenses are effective with an 82% success rate (as defined by VA, comfort, and corneal physiology) and a mean duration of wear of 2.5 years [ 33 ]. YK lenses have also been shown to be effective with 94.5% of eyes achieving a VA of 20/40 (6/12) or better (average VA 0.79 ± 0.21 Snellen decimal). It also has relatively high patient comfort levels, with 97.6% of eyes tolerating the contact lens with a mean wearing time of 12.1 h per day and 90.7% reporting that the lenses were comfortable [ 34 ]. In another study reported by Lee et al., YK lenses improved efficacy and comfort in keratoconus patients [ 35 ]. Overall, 71.6% of eyes achieved a VA of 20/30 or better, 94% tolerated the fitting, 85% reported complete comfort, and the mean wearing time was 11.9 h per day [ 35 ].

Non-comparative studies—scleral and hybrid lenses

Fitting corneal GP lenses in advanced cases of keratoconus can be challenging as a result of lens decentration, dislocation, or discomfort. Scleral and hybrid lenses have been shown to provide good VA and comfort for keratoconic patients, some of whom were previously intolerant to RGP (Table 5 , Figs.  2 – 5 ). The advantages of scleral lenses over GP lenses are increased comfort and stability of lens wear. Scleral lenses with their large diameter allow for vaulting over the irregular and steep corneas and therefore have an increasing role in the treatment of corneal ectasia, providing another viable nonsurgical option. In general, scleral lenses are more comfortable than corneal GP lenses since there is no contact with the cornea which has more innervation than the sclera. Also, their larger diameter results in a more comfortable lens-to-lid interaction. In the recent years, newer scleral lens designs have expanded the scope of contact lens wear in keratoconus patients. The current recommendation by the Scleral Lens Education Society is to move away from using diameter classification in scleral lens nomenclature since it would not be accurate for extremely large or small eyes [ 36 ]. Instead, scleral lenses are classified based on the resting zone area of the lens on the ocular surface. Corneal lenses (Fig. 1 ) are lenses which rest entirely on the cornea, corneo-scleral lenses (Figs. 2 – 4 ) are lenses which rest partly on the cornea and partly on the sclera and scleral lenses (Fig. 5 ) are lenses which rest entirely on the sclera [ 36 ]. In this paper, we will use this new classification and refer to semi-scleral lenses as corneo-scleral lenses (Table  6 ).

a Left eye Orbscan topography: vertical bowtie pattern on the keratometry map showing residual high with-the-rule astigmatism. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Refraction: +2.75/−12.50 × 165° [6/9]; Rose K corneo-scleral lens 6.40 mm BC/−11.00 D/14.40 mm Dia [6/7.5]).

a Left eye Pentacam tomography showing an inferior steepening pattern on keratometry map with corresponding posterior elevation on the posterior elevation map. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Refraction: −0.25/−4.00 × 105° [6/6]; Capricornia corneo-scleral lens 7.00 mm BC/−7.75 D/13.50 mm Dia [6/6]).

a Right eye Pentacam tomography showing an inferior steepening pattern on keratometry map with corresponding posterior elevation on the posterior elevation map. b Right eye cobalt blue filter image with fluorescein dye showing an apical bearing fit pattern. (Refraction: pl/−8.00 × 95° [6/15]; Capricornia corneo-scleral lens 6.80 mm BC/−10.50 D/13.50 mm Dia [6/7.5]).

a Right eye slit lamp photograph showing a well centered scleral lens with adequate corneal clearance. b Adequate scleral lens edge lift with no blanching of the conjunctival vessels seen. (F4 lens [Innovative Sclerals, UK] 8.27BC/−0.25D/14.50 mm scleral radius/23 mm overall diameter [6/9]).

The Rose K2 XL lens, a corneo-scleral contact lens, provided good visual acuity (BCLCVA 0.09 logMAR) and comfort for patients with irregular corneas [ 37 ]. In patients unsuitable for conventional GP lens wear, scleral lens wear could be a good alternative, with all patients in a study achieving a BCLCVA of 6/12 (20/40) or better [ 38 ]. In patients with corneal ectasia, prosthetic replacement of the ocular surface ecosystem (PROSE) custom lens wear has been shown to be effective with a lens wear of 88% at 6 months and an improvement in NEI VFQ-25 score of 27.6 points ( p  < 0.001) on a 100-point scale [ 39 ]. PROSE custom lenses are designed by using proprietary computer-assisted design and manufacture US patented software that is linked to a manufacturing lathe to create a smooth lens surface and to allow for control of the vault of the lens independent of base curve radius. PROSE treatment is an excellent alternative to keratoplasty for eyes with ectasia that are contact lens intolerant. Jupiter scleral lenses (15.0–24.0 mm in diameter) have also been shown to produce good results with 73% of patients reporting a BCLCVA of 20/30 (6/9) or better and 78% finding the lens comfortable in a study by Pecego et al. [ 40 ]. In a Korean population, MSD miniscleral lenses (15.8 mm) are also suitable for keratoconus patients, with a mean logMAR acuity of 0.10 ± 0.11. Overall, 97% of patients reported comfortable lens wear and the mean daily lens wear time was  10.1 ± 2.3 h [ 41 ]. Bitangential scleral lenses (20 mm) are effective for keratoconus with a median decimal BCVA of 0.8 in one study [ 42 ]. Bitangential scleral lenses have a non-rotationally symmetrical periphery that aims to enable gentle positioning on the scleral surface, increasing fitting tolerance and optimal centration. A new bitangential mini-scleral lens has also been developed by Otten et al. (Visser Contact Lens Practice, Nijmegen-Utrecht, the Netherlands) (median diameter 16 mm; range: 15.5–17 mm). These lenses provided good VA with a median BCLCVA of 0.022 (logMAR) and were comfortable (79% reported a comfort score of either a 4 or 5 (out of 5), 82% wore their lenses 12 h or longer a day) [ 43 ]. A study by Koppen et al. showed that scleral lenses reduce the need for corneal transplants in severe keratoconus, with 40 out of 51 eyes successfully treated with long-term scleral lens wear instead of undergoing corneal transplant surgery and a mean gain in VA (lens vs. spectacle-corrected VA) of 0.54 ± 0.18 (decimal) [ 44 ]. SoftPerm hybrid lenses are also effective with 83.3% achieving 20/40 or better VA [ 45 ]. However, SoftPerm lenses were fraught with complications such as corneal neovascularization, poor tear exchange, and tearing of the lens at the junction of the soft and GP portions and as such, these lenses were discontinued in 2010.

Post corneal cross-linking

GP lens wear post-CXL is relatively well-tolerated (Table 7 ), likely due to decreased corneal sensitivity and the flattening effect of CXL [ 46 ]. Unlu et al. found that after CXL, the mean duration of GP lens wear increased from 6.4 h/day (pre-CXL) to 12.6 h/day (3 months post-CXL) and 13.2 h/day (6 months post-CXL) [ 46 ]. However, certain problems have been identified in the use of GP lenses post-CXL. Sehra et al. evaluated the effect of GP lens wear after corneal cross-linking in keratoconus patients and noted that there is a delay in the regeneration of the corneal sub-basal nerve plexus when compared with spectacle lens wear after cross-linking [ 47 ].

For scleral lenses, the duration of lens wear remained stable at a mean of 16 h/day both pre-CXL and 1-year post-CXL [ 48 ]. A good VA of 0.03 logMAR was achieved [ 48 ]. In a prospective interventional case series by Singh et al, GP lenses were fitted in post-CXL patients [ 49 ]. BCLCVA post-CXL initially worsened from a pre-operative level of 0.21 ± 0.27 logMAR to 0.51 ± 0.15 logMAR ( p  = 0.000) at 2 weeks post-CXL before gradually improving to 0.01 ± 0.10 logMAR ( p  = 0.012) at 6 months post-CXL. Contrast sensitivity assessed by FACT chart also improved from 1.1 ± 3.9 to 1.3 ± 0.2 (lowest spatial frequency, p  = 0.000) and from 0 to 0.3 ± 0.3 (highest spatial frequency, p  = 0.002) at 6 months follow up. Keratometric values were also significantly reduced 6 months postoperatively and duration of contact lens use increased from 1.25 ± 1.80 h preoperatively to 9 ± 1.89 h 6 months postoperatively ( p  = 0.000) [ 49 ].

Post intrastromal corneal ring segment (ICRS)

As a result of modification of the corneal shape after ICRS implantation, contact lens fitting may be more challenging, especially GP lens fitting. Hence the use of different types of lenses (soft, scleral, corneoscleral, and piggyback) has been investigated in patients who previously underwent ICRS implantation. Overall, these lenses show good efficacy in the treatment of keratoconus post-ICRS implantation with good VA and function (Table 7 ). Similar to non-ICRS keratoconic patients, SCL fitting was only successful in Stage I and II keratoconus (mild to moderate), with 75% and 66.66% of post-ICRS patients respectively successfully fitted, whereas none of the patients with stage III keratoconus were fitted successfully [ 50 ]. Piggyback lenses were a good alternative for such patients [ 50 ]. Kerasoft IC lenses are effective in post-ICRS patients with low rates of complications and adequate VA and wearing time [ 51 ]. Kerasoft IC lenses (14–15.50 mm) (Ultravision International Limited, Bedfordshire, UK) are custom-lathe soft SiHy lenses that allows for a customized selection of central and peripheral regions. SCL central thickness equal or superior to 0.4 mm affects visual function in patients post-ICRS by decreasing ocular high order aberration (HOA) and improving visual function [ 52 ]. A corneo-scleral lens (Scleracon, Lenticon, Madrid, Spain; diameter: 12.60–13.50 mm) was designed with a multi-aspherical geometry design based on three curves (base curve, intermediate or small transition curve, and peripheral or scleral curve) [ 53 ]. This lens provided good VA (BCLCVA: 0.00 ± 0.12 [logMAR]; BSCVA: 0.22 ± 0.17 [logMAR]; p  < 0.001), a 33% decrease in total HOAs  (from 2.62 ± 1.31 to 1.75 ± 1.81 μm; p  < 0.009) and an improvement in spatial frequencies of contrast sensitivity (all p  < 0.05). The lens was also comfortable with 70.37% of patients reporting high ratings of subjective visual quality and mean wear time of 11.78 ± 3.93 h [ 53 ].

Post penetrating keratoplasty (PK)

In patients who previously underwent (PK), contact lens wear is sometimes necessary for residual refractive error or recurrent disease. Contact lens fitting may be challenging after PK because of the corneal profile which is usually centrally flat and peripherally steep as a result of the graft–host junction. GP lenses usually lead to decentration and intolerance. The use of hydrogel lenses is limited due to the inability of these lenses to correct irregular or highly astigmatic corneas. In recent years, miniscleral RGP, scleral, and large diameter RGP lenses have been shown to be effective (Table 7 ). Miniscleral RGP lenses (ESCLERA™ contact lenses—Mediphacos, Buritis, MG, Brazil) were particularly successful in post PK patients previously unable to wear GP contact lenses [ 54 ]. However, lens use was discontinued in four eyes and microbial keratitis developed in one eye during follow-up [ 54 ]. BCVA obtained with the Jupiter scleral lenses (15.6–18.4-mm diameter) (Essilor Contact Lens Division, Dallas, TX) have been shown to be better than prior spectacle refraction or habitual contact lenses (most commonly GP) by two BCVA lines [ 55 ]. Overall, 91.7% of eyes achieved functional vision with BCLCVAs (Jupiter scleral lens) of 20/40 or better [ 55 ]. Tricurve RGP lenses with large diameters (12 mm) have been successfully fitted in 47% of 190 PK patients with good tolerance at the Rotterdam Eye Hospital [ 56 ].

Assessing satisfaction

Patient comfort and satisfaction while wearing contact lenses is an important factor that affects patient compliance. The relationship between rigid contact lens comfort and keratoconus disease severity is still equivocal (Table 8 ). In the CLEK study, Edrington et al. identified factors associated with rigid contact lens comfort in keratoconus patients and found no association between decreasing patient-reported comfort and increasing disease severity as measured by steep keratometry or first definite apical clearance lens [ 57 ]. However, Wu et al. found that patients with severe keratoconus showed significantly reduced wearing time, NEI-VFQ-25 scores and overall satisfaction compared with patients with mild-to-moderate keratoconus [ 58 ].

According to the CLEK study, the apical fitting relationship (flat vs. steep) does not appear to be associated with patient-reported comfort. Minimal peripheral clearance may contribute to decreased rigid contact lens comfort in keratoconus [ 57 ].

The impact of contact lens wear on quality of life in keratoconus patients appears to be similar between RGP, hybrid, soft toric, and silicone-hydrogel keratoconus lenses as can be seen by similar scores on the Contact Lens Impact on Quality of Life (CLIQ) Questionnaire [ 59 , 60 ]. Scleral lenses (17–18.2 mm) have a higher patient-reported comfort and satisfaction as compared with habitual lenses (mainly GP but also include soft, piggyback, and hybrid lenses) though midday fogging remains a limitation for many wearers [ 61 ]. Scleral lenses with their large diameter allow for vaulting over the irregular and steep corneas and also enable for more comfortable lens wear as the edge of the lens is not felt while blinking.

However, a significant limitation in the assessment of quality of life in keratoconus patients is the lack of validated quality of life questionnaires specific for the keratoconus population [ 62 ].

Complications

Corneal structural changes.

Contact lens use in keratoconic patients has been associated with various structural changes such as decreased basal epithelial cell density, stromal keratocyte density, and endothelial cell count. Basal epithelial cell density has already been shown to be decreased in patients with keratoconus [ 63 , 64 , 65 ]. GP contact lens wear further decreases the basal epithelial cell density as compared with non-contact- lens-wearing keratoconus patients [ 66 , 67 ]. Patel et al. postulated that this decrease in basal epithelial cell density was due to the pathophysiology of keratoconus further worsened by contact lens wear [ 68 ]. Many studies have shown a decrease in stromal keratocyte density in keratoconic corneas as compared with normal corneas [ 67 , 69 , 70 , 71 ]. The effect of contact lens use on keratocyte density in keratoconus patients is still equivocal. Some studies have shown a further significant decrease in stromal keratocyte density in keratoconus patients who wear contact lenses (both GP and soft lenses) as compared with non-contact- lens-wearing keratoconus patients [ 66 , 69 ], while others report no statistically significant difference between the two groups [ 65 , 67 ]. Most of these studies looked at the effect of GP lenses on the corneal structure [ 66 , 67 ], one study included both GP and soft lenses [ 69 ] and one study did not specify the type of contact lens used [ 65 ]. It has been hypothesized that contact lens wear causes epithelial injury which triggers the production of apoptotic cytokines which reduce keratocyte density [ 69 ]. Conversely, a study by Acar et al. demonstrated an increase in posterior keratocyte density in piggyback and ClearKone lens wearers [ 72 ]. Endothelial cell count has been shown to be decreased by up to 18% in keratoconic patients using SoftPerm lenses but not in keratoconic patients using GP or soft lenses [ 70 , 73 ]. The low oxygen permeability rates of SoftPerm lenses as compared with GP and soft lenses could explain the lower endothelial cell counts observed. Cases of significant corneal edema have also been reported in keratoconus patients wearing hybrid lenses (SoftPerm and ClearKone SynergEyes), likely due to corneal hypoxia [ 74 , 75 ]. Other manifestations of corneal hypoxia in SoftPerm lens wear include peripheral corneal neovascularization [ 45 ].

A few studies have shown a link between keratoconus and dry eye, with a higher prevalence of clinical signs such as lower tear break up times (TBUT) and corneal staining, a higher concentration of pro-inflammatory markers such as interleukins and metalloproteinases in keratoconus patients [ 76 , 77 , 78 ]. GP wear has been shown to further exacerbate dry eye signs and symptoms in keratoconus patients. In a study by Carracedo et al., among keratoconus patients, GP wearers had lower Schirmer test scores and TBUT, higher diadenosine tetraphosphate (Ap4A) concentrations and higher symptom scores (McMonnies questionnaire) as compared with spectacle wearers [ 79 ]. A study by Moon et al. also found lower TBUTs and goblet cell densities in patients wearing GP for keratoconus or myopia [ 80 ]. Acar et al. found increases in IL-6 and IL-8 levels in keratoconus patients wearing piggyback and ClearKone contact lenses [ 72 ]. Conversely, scleral lenses have been noted to improve signs and symptoms of dry eye. A different study by Carracedo et al. showed that scleral lens wears had significantly lower Ocular Surface Disease Index scores and tear osmolarity but no changes were observed in Schirmer test scores and TBUT [ 81 ]. Ocular discomfort due to dry eye could contribute to increased eye rubbing seen in patients with keratoconus, a risk factor for keratoconus progression [ 82 , 83 ].

Infectious keratitis, though rare, is one of the most sight-threatening complications of contact lens wear. The type and material of contact lens affects the risk of keratitis and there is currently no study that shows that keratoconus patients have different incidences of infective keratitis than any other patients wearing similar types of contact lenses. In an epidemiological study performed in Australia, the annualised incidence of microbial keratitis per 10,000 wearers was lowest in daily wear GP CL wearers at 1.2 (confidence interval [CI], 1.1–1.5).  In order of increasing incidence of microbial keratitis per 10,000 wearers are the following lenses: daily wear soft CL wearers at 1.9 (CI, 1.8–2.0); daily disposable CL wearers at 2.0 (CI, 1.7–2.4); soft CL wearers (occasional overnight use) at 2.2 (CI, 2.0–2.5); daily disposable CL wearers (occasional overnight use) at 4.2 (CI, 3.1–6.6); SiHy CL wearers (occasional overnight use) at 5.5 (CI, 4.5–7.2); daily wear SiHy CL wearers at 11.9 (CI, 10.0–14.6); overnight wear soft CL wearers at 19.5 (CI, 14.6–29.5) and inovernight wear of SiHy at 25.4 (CI, 21.2–31.5) [ 84 ]. Hence the incidence of contact lens-related microbial keratitis was lowest in GP lens wearers, higher in soft lens wearers and the highest in overnight soft lens wearers [ 84 ]. In keratoconus patients, acanthamoeba keratitis has been reported in scleral lens users [ 85 ]. Possible risk factors suggested for microbial keratitis in scleral lens wearers were the large diameter of the contact lens which predisposes  to corneal hypoxia, the use of large amounts of saline solution for scleral lens fitting and poor lens storage [ 85 ]. Noninfective keratitis has also been reported in a keratoconus patient wearing mini-scleral lenses [ 86 ].

Fitting techniques

There has been a change in the contact fitting technique for keratoconus over the years from an apical touch to a three-point touch technique. Zadnik et al. reported on the safety and efficacy of flat- and steep-fitting rigid contact lenses in 761 keratoconus eyes in the CLEK study [ 87 ]. The results showed that, contrary to popular belief, keratoconic eyes fitted with an apical touch fluorescein pattern did not have an increased risk of being scarred centrally at baseline [ 87 ]. However at the end of the study there was a significant difference in the development of scarring and in the likelihood of requiring PK between flat fit lens patients and apical clearance fit lens patients. Another study compared the three-point-touch and apical touch fitting approaches in Rose K2 GP lenses in 109 eyes [ 88 ]. No statistically significant differences in optimal lens fit rates were found between three-point-touch and apical touch fitting approaches and between nipple and oval cones [ 88 ]. Sorbara et al. performed a retrospective review on the use of corneal topography to determine the types of keratoconus (centred or nipple, oval cones, severe cones or pellucid marginal degeneration (PMD)) and the type of GP lens that fitted optimally based on the type of keratoconus [ 89 ]. Inventory sets for keratoconus that had progressively smaller BOZDs (back optic zone diameter) as the base curve steepened were found to fit best when prescribed for centred or nipple cones and those that had a constant BOZD with a certain lens diameter that did not vary with the base curve were found to perform better on oval cones. Very large cones, as with PMD benefited from lenses with very large BOZDs [ 89 ].

Several studies looked at topographical predictors of the best base curve radius for GP lens fitting. The predictors include: K-minimum for pancorneal GP lens fitting [ 90 ], 5-mm average keratometry on the axial map for Rose K lens fitting [ 91 ], anterior chamber depth on Pentacam corneal tomography for Esclera (R) scleral contact lens fitting [ 92 ], and mean weighted corneal sagittal height at a 7.4-mm chord for ClearKone lens fitting [ 93 ].

Computerized contact lens fitting has been shown to reduce chair time in contact lens fitting and improve visual performance. A new web-based algorithm (free access at www.calculens.com ) for selecting the back-optic zone radius of spherical GP lens in keratoconus eyes was found to improve spherical KAKC GP fitting (Conoptica) [ 94 ]. Two studies compared FITSCAN (a contact lens fitting software in built in the Orbscan TM II z (Bausch & Lomb Surgical, Rochester, NY)) and conventionally fitted GP lenses and found that there was a slight bias towards flatter apical fitting in the Fitscan design [ 95 , 96 ]. One of the studies showed that selecting the BC of the initial trial lens 0.22 mm steeper than the FITSCAN calculated base curve may help to reduce the complexity of GP contact lens fitting in keratoconus [ 95 ]. Wavefront-guided scleral lens correction in keratoconus optically compensates for HOA  concomitant with the disease and can provide visual image quality equivalent to that seen in normal eyes [ 97 ].

EyePrintPRO (Advanced Vision Technologies, Lakewood, Colo.), a new customized impression-guided scleral lens fitted with 3D technology, was recently developed [ 98 ]. After creating an impression mold over the ocular surface using polyvinyl siloxane material, the mold is then scanned with a 3D scanner. Lathe technology is subsequently used to create the posterior surface of the scleral lens according to the contours of the mold [ 98 ].

A piggyback lens fitting study found that negative-powered SCLs provide a flatter anterior surface in comparison with positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting [ 99 ].

Scheimpflug imaging and anterior segment optical coherent tomography (ASOCT) are useful in scleral contact lens fitting [ 92 , 100 ]. Pentacam (Oculus, Germany) measurements such as anterior chamber depth and pentacam-measured corneal height can be good predictors of the most appropriate Esclera lens to be fitted in keratoconus patients [ 92 ]. Likewise, corneal sagittal height measured with Visante OCT (Carl Zeiss, Germany) is an effective method of determining the appropriate lens/cornea relationship for scleral contact lenses [ 100 ]. The scleral lens vault (PROSE, Boston Foundation for Sight, Needham Heights, MA, USA) measured with ASOCT reduced significantly after 4 h of lens wear during scleral lens trial indicating that the final assessment of the scleral lens may be performed after 4 h of lens wear [ 101 ]. In another study, the corneal sagittal height measured with the Visante OCT showed a likelihood of clearance loss after 1 h of scleral lens wear [ 102 ]. Esen et al. looked at the influence of apical clearance on mini-scleral lens settling, clinical performance, and corneal thickness changes [ 103 ]. The average amount of settling was 62.8 μm after 8 h, 80% of which occurred during the first 4 h. Settling rate was significantly lower in the low apical clearance group ( P  = 0.01) with the smaller diameter lenses settling more ( P  = 0.03). Slight corneal swelling (1.3%) occurred after 8 h of wear. Another study looked at anterior corneal curvature and aberration changes after scleral lens wear in keratoconus patients with and without ring segments and found that short-term scleral lens wear showed flattening of the anterior corneal surface in all subjects [ 50 ].

Spectral domain OCT can image and measure the tear film thickness in keratoconic patients with different fitting patterns of GP lenses, in particular Rose K2 lenses and can be used to evaluate and modify the lens parameters to increase patient satisfaction. Lens intolerance may be related to edge lift rather than central fitting [ 104 ].

Despite advances in the surgical treatment of keratoconus, contact lenses remain an important and popular option for visual rehabilitation in keratoconus, with various designs enabling a large proportion of patients to attain satisfactory VA. [ 12 , 13 , 14 , 16 , 17 , 18 , 57 ] New contact lens designs and materials have significantly expanded the available fitting options for keratoconus patients.

GP lens wear provided significantly better vision and improved three-dimensional depth perception as compared with glasses [ 20 , 21 ]. Among GP lens types, special cone lens design lenses such as Rose K lenses had better patient comfort levels though there was no difference in BCLCVA among the GP lenses [ 19 , 20 , 21 , 23 ].

Soft lenses show good efficacy for the treatment of mild-to-moderate keratoconus with newer designs improving visual performance such as customised hydrogel contact lenses incorporating vertical coma correction and novel pinhole soft lens reducing higher order aberrations [ 29 , 30 , 31 ].

Scleral and hybrid lenses provide good VA and comfort for keratoconic patients, some of whom were previously intolerant to GP lenses [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. Newer design scleral lenses have expanded the scope and comfort of contact lens wear for keratoconus patients. GP lens wear post-CXL is relatively well-tolerated, likely due to decreased corneal sensitivity and the flattening effect of CXL [ 46 ]. Contact lenses may still be required post intrastromal corneal ring procedures and post keratoplasty and in these conditions, custom soft lenses and scleral lenses are more successful than GP lenses due to the altered post-surgical corneal shape.

Imaging technology, such as corneal topography and anterior segment optical coherence tomography, can be utilized to guide contact lens fitting and to better understand the corneal microstructural changes associated with contact lens wear. Several topographical predictors of the best base curve radius for GP, scleral and hybrid lens fitting and computerized contact lens fitting techniques are now available which reduce the complexity and chair time of lens fitting as well as improving comfort and visual performance [ 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 ]. A new customized impression-guided scleral lens fitted with 3D technology was recently developed which further improved the accuracy of scleral lens fitting [ 98 ].

Future areas of research such as comparative studies to analyse the efficacy and comfort of the various contact lens types and validated quality of life questionnaires specific to the keratoconus population would enhance discussion on this subject. Another area of future research would be to compare the outcome of contemporary surgical options for keratoconus to that of contact lens wear.

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Lim, L., Lim, E.W.L. Current perspectives in the management of keratoconus with contact lenses. Eye 34 , 2175–2196 (2020). https://doi.org/10.1038/s41433-020-1065-z

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A Case of Early Keratoconus Associated with Eye Rubbing in a Young Child

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• Published: 15 June 2020
• Volume 9 , pages 667–676, ( 2020 )

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• Victoria Dimacali 1 , 2 ,
• Miltos Balidis 1 ,
• Aspasia Adamopoulou 1 ,
• Athina Kozei 1 , 3 , 4 &
• Nikolaos Kozeis 1 , 3  

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Introduction

Keratoconus usually presents during puberty and is considered rare in young children.

Case report with clinical findings and computerized corneal tomography.

We report the case of an 8-year-old girl with early bilateral keratoconus who presented with allergic conjunctivitis and persistent eye rubbing. Although our patient did not exhibit steep keratometry, early cones and inferotemporal thinnest corneal thicknesses were detected in both eyes using Scheimpflug imaging (Oculus GmbH Pentacam, Wetzlar, Germany). Belin/Ambrósio total D values were 1.85 on the right and 2.11 on the left. Improvement in best-corrected visual acuity was noted after treatment of allergic eye disease, and corneal tomographic findings remained stable 4 months after initial consult.

This is a case of early diagnosed keratoconus in a young patient. Diagnosis of this condition in young children is challenging, as these patients are less likely to report visual complaints, and clinical examination is usually unremarkable. Keratoconus screening should be considered in children with atopy and eye rubbing behavior regardless of age, even in those with no other associated pathology and with negative family history.

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Keratoconus (KC) is an ocular disorder in which there is progressive thinning and ectasia of the cornea due to alterations in its collagen structure [ 1 ]. It is associated with blurring of vision, light sensitivity, myopia, and irregular astigmatism, and may occasionally result in corneal scarring and acute corneal edema. Both eyes are affected although one eye may precede the other [ 2 ]. At present, no primary pathophysiologic explanation for keratoconus has been elucidated, as it is probably caused by various environmental, biomechanical, genetic, and biochemical disorders [ 3 ].

Keratoconus often presents during the second decade of life. It can be isolated or associated with other ocular and systemic disorders including vernal keratoconjunctivitis, atopy, Down syndrome, intellectual disability, and Leber congenital amaurosis [ 3 , 4 , 5 ]. However, it is considered a rare condition in young children [ 4 , 6 , 7 ].

Although vigorous eye rubbing seems to be a significant risk factor for keratoconus, the exact mechanism involved is still unknown [ 3 , 4 , 8 , 9 ]. Here we present the case of a young child with early keratoconus (EKC) with frequent eye rubbing due to allergic eye disease. Data regarding EKC in very young children are still limited, and any new reports are important. The study was conducted according to the tenets of the Declaration of Helsinki and was approved by the Ophthalmica Eye Institute Ethics Committee. The parents of the patient signed an informed consent form for publication of the case and the patient’s clinical details.

Case Presentation

An 8-year-old girl was referred to our clinic for blurred vision in both eyes, reportedly starting 2 weeks prior to consult. Although her past ocular, medical, and family histories were otherwise unremarkable, her parents mentioned that she often rubbed her eyes vigorously. Her cycloplegic refraction was +0.25/−0.50/175° and +0.50/−0.75/180° for the right and left eyes, respectively, and her best-corrected visual acuity (BCVA) was 20/30 in both eyes. The findings from the ocular (clinical and paraclinical) and orthoptic examinations proved unremarkable. Both corneas were clear and had no clinical signs of ectasia, while the conjunctivae were mildly erythematous with some papillae.

Computerized corneal tomography was performed using rotating Scheimpflug imaging (Oculus GmbH Pentacam, Wetzlar, Germany). The curvature maps showed asymmetric bow-tie astigmatism, with a significantly skewed radial axis of almost 60° on the right, and asymmetric vertical D pattern astigmatism on the left (Fig.  1 ). Kmax was only 43.5D on the right and 44.1D on the left, and anterior astigmatism was 0.5D and 0.8D, respectively. Pachymetry at the apex was 501 μm on the right and 504 μm on the left, with thinnest corneal thicknesses (TCT) of 496 μm and 492 μm located inferotemporally in both eyes [−0.62/−0.55 and +1.02/−0.68 ( x / y ), respectively]. The Belin/Ambrósio Enhanced Ectasia Display total D values (BAD-D) were 1.85 on the right and 2.11 on the left (Fig.  2 ). Abnormalities were also detected in the anterior elevation maps of both eyes, as well as the anterior elevation value of the left eye at its thinnest point. Posterior elevation maps on best-fit sphere mode showed isolated islands in both eyes, with maximum elevation values corresponding to the TCT location in the left eye.

Pentacam maps of both eyes taken at initial consult. Curvature maps show asymmetric bow-tie astigmatism on the right and asymmetric vertical D pattern astigmatism on the left

Belin/Ambrósio Enhanced Ectasia display of both eyes at initial consult. The total D values were 1.85 on the right and 2.11 on the left. Pachymetric progression maps were within normal limits

The BAD is a feature of the Pentacam, which uses data from elevation maps, pachymetry, best-fit sphere, and enhanced reference surface in a regression analysis to arrive at an overall “D” value, or BAD-D, which reflects the probability of ectasia [ 10 ]. The current version is the BAD III, which utilizes nine tomographic parameters [ 11 ]. Studies have shown that among the keratometric, pachymetric, and posterior elevation indices, the D value has the highest area under the receiver operating characteristic curve in differentiating between clinical and subclinical keratoconus (SKC) eyes and control eyes [ 12 , 13 ].

A D value of 1.88 was found by one study to identify 99% of known KC cases, with a false-positive rate of 2.5% [ 10 ]. Cut-off points in use for SKC in the literature are 1.45 by Ambrósio et al. [ 14 ], 1.54 by Hashemi et al. [ 15 ], and 1.61 by Ruiseñor Vazquez et al. [ 16 ]. A cross-sectional study which included SKC and KC eyes and normal eyes found that the best cut-off D value was 1.83 for identifying clinical KC from controls (100% sensitivity and 96.0% specificity), and 1.73 for differentiating bilateral SKC eyes from normal eyes (96.7% sensitivity and 79% specificity) [ 12 ].

The D values of our patient were greater than 1.73 in both eyes. The left eye, which had the higher BAD-D, also showed a suspicious vertical D pattern. This pattern has been proposed to reflect horizontal asymmetry in patients with suspected KC [ 17 ].

We treated the patient for 2 weeks with topical ketotifen 0.1 mg/0.4 mL twice a day, fluorometholone 0.1% four times a day, and preservative-free sodium hyaluronate gel four times a day, to reduce the discomfort and pruritus. She was also verbally encouraged by her parents to refrain from rubbing her eyes.

Two weeks later, the BCVA improved to 20/25 on the right eye and 20/20 on the left, and the refractive error decreased to +0.25D sphere in both eyes. The parents reported that the child’s eye rubbing had decreased significantly, so we decided to gradually taper off the medications and to do repeat imaging on the next follow-up.

Four months later, the BCVA was 20/20 in both eyes. The repeated imaging showed a slight increase in inferior steepening by 0.3D on the right and 0.2D on the left eye, while TCT and anterior and posterior elevation maps were stable (Fig.  3 ). We decided to have the patient follow up after 6 months and monitor her regularly thereafter.

Pentacam maps of both eyes taken 4 months after initial consult and initiation of medical therapy. Although there is mildly increased inferior steepening, TCT values and elevation maps remained stable in both eyes

Keratoconus usually presents during puberty and is relatively rare in young children. It is not typically suspected in the pediatric population when there are no other ocular and systemic associations and no family history. A large retrospective study of patients examined at a tertiary eye center in Lebanon found that only 0.53% of patients younger than 15 years of age were diagnosed with KC. The youngest patient with keratoconus was 9 years old. In general, those pediatric cases represented 2.96% of all keratoconus cases [ 6 ]. A retrospective study in a pediatric population in Saudi Arabia similarly detected keratoconus in 2.30% of patients 6 to 16 years of age [ 18 ]. The youngest patients with keratoconus reported so far in the literature are a 4-year-old girl from Turkey and a 4-year-old girl with Down syndrome from Switzerland [ 4 , 7 ]. Although limited data presently exists about EKC in young children, detection of ectatic disease at younger ages is expected to increase as imaging techniques become more advanced and awareness about screening improves. Our patient was 8 years old at presentation. Although she did not exhibit steep keratometry, Pentacam imaging of both eyes demonstrated localized steepening and an asymmetric bow-tie pattern, as well as inferotemporally displaced thinnest corneal points. Central corneal thicknesses and TCTs were also less than 500 μm in both eyes. This meets the standard diagnostic criteria proposed by Martinez-Abad et al. for SKC [ 19 ]. The main signs which must both be met are corneal topography with abnormal localized steepening or an asymmetric bow-tie pattern, and normal-appearing cornea on slit lamp biomicroscopy. Complementary signs, one of which must be met, are the following: keratometric power greater than 47.0D, oblique cylinder greater than 1.50D, central corneal thickness less than 500 μm, and clinical keratoconus in the fellow eye. Further investigation with corneal biomechanical analysis and epithelial mapping may also be done especially when clinical and tomographic findings are equivocal.

The 4-year-old girl from Turkey who was eventually diagnosed with keratoconus was a vigorous eye rubber presenting with decreased vision [ 4 ]. Our patient was similarly an eye rubber who presented with slightly reduced visual acuity. The association between eye rubbing and keratoconus is well known. A retrospective study found eye rubbing behavior to be present in 91.84% of patients diagnosed before age 15, which was significantly higher than 70.06% of those diagnosed after age 27 [ 20 ]. Another study found eye rubbing to be present in 79% of a pediatric population, with all patients showing clinical signs of allergic eye disease [ 5 ]. Although the exact mechanism by which keratoconus may develop remains to be elucidated, McMonnies proposed the following responses to occur due to eye rubbing: increase in corneal temperature, epithelial thinning, increased inflammatory mediators in the tear film, abnormal enzyme activity, intraocular pressure spikes, high hydrostatic tissue pressure, thixotropic decrease in ground substance viscosity, temporary displacement of ground substance from the corneal apex, curvature transfer to the cone apex, slippage between collagen fibrils at the cone apex, changes to keratocytes, and corneal scarring [ 21 ]. Eye rubbing has also been shown to raise the levels of tear metalloproteinase-13, IL-6, and TNF-α in both normal and keratoconic eyes [ 1 ].

Ectasia progression has been defined as steepening of the anterior or posterior corneal surface, or a thinning and/or an increase in the rate of corneal thickness change from the periphery to the thinnest point, with the changes being consistent over time and above the normal variability of the measurement system. A decrease in best-spectacle-corrected visual acuity, although often noted, is not necessary in documenting progression [ 3 ]. In our case, corneal tomographic findings remained stable over the next 4 months. In the case of the 4-year-old girl from Switzerland with Down syndrome who had rapid progression of keratoconus, stabilization of the tomographic measurements and visual acuity was achieved after consecutive bilateral collagen cross-linking [ 7 ].

Corneal collagen cross-linking (CXL) must be offered when any sign of progression is noted. The efficacy and safety of CXL in adults has been well established, but experience in the pediatric population is limited. Recent studies have demonstrated that conventional epithelium-off CXL is safe and effective in preventing progression for up to 10 years [ 22 ]. Accelerated CXL has also been shown by some studies to be safe and effective in children in slowing or preventing the progression of keratoconus for up to 3 years [ 23 , 24 , 25 ].

Early detection of keratoconus and its subclinical forms in young children is important albeit challenging, especially in patients with no evident risk factors or family history. Advanced cases at the time of diagnosis usually progress more rapidly in young children than in adults [ 6 , 26 , 27 ]. Nonsurgical management of KC should include verbal guidance to avoid eye rubbing, use of topical anti-allergic medication in patients with allergy, and use of lubricants for ocular irritation [ 3 ]. In early cases, control of the allergic reaction to decrease the eye rubbing impulse may reduce the inflammation and help avoid corneal complications [ 28 ]. Salomao et al. [ 29 ] stress the need for screening; though moderate and advanced cases of keratoconus are easily recognized, identification of mild and early forms of keratoconus remains a challenge. Ambrósio et al. [ 30 ] note that control of allergy and inflammation of the ocular surface is important, and new advances in diagnosis based on artificial intelligence, genetics, and other methods will increase the accuracy of diagnosis and lead to customized treatment planning. Our patient’s visual acuity improved and her tomographic profile remained stable just with conservative treatment. With this case, we would like to highlight the entity of EKC in very young children and the importance of screening in specific patients, since young children are less likely to report functional complaints and the cornea, by definition, appears normal upon clinical examination. The combination of suspicious eye rubbing behavior and symptoms should prompt further investigation.

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Acknowledgements

We would like to thank our patient and her parents for giving their consent for the publication of this case.

No funding or sponsorship was received for this study or publication of this article.

All named authors meet the International Committee of Medical Journal Editors (ICMJE) criteria for authorship for this article, take responsibility for the integrity of the work as a whole, and have given their approval for this version to be published.

Disclosures

The authors Victoria Dimacali, Aspasia Adamopoulou, Miltos Balidis and Athina Kozei declare that they have no conflict of interest. Nikolaos Kozeis is a member of the journal’s Editorial Board. It should also be noted that after the completion of the manuscript, the following occurred: author Nikolaos Kozeis changed his affiliation from “Ophthalmica” to “Pediatric Eye Centre of Greece, Thessaloniki, Greece”. Athina Kozei changed one of her affiliations from “Ophthalmica’’ to “Pediatric Eye Center of Greece, Thessaloniki, Greece”, and she retained the second one, School of Pharmacology, University of Nicosia; Nicosia, Cyprus.

Compliance with Ethics Guidelines

The study was conducted according to the tenets of the Declaration of Helsinki and was approved by the Ophthalmica Eye Institute Ethics Committee. The parents of the patient signed an informed consent form for publication of the case and the patient’s clinical details.

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Data sharing is not applicable for this article as no data sets were generated or analyzed during the current study.

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Victoria Dimacali, Miltos Balidis, Aspasia Adamopoulou, Athina Kozei & Nikolaos Kozeis

Makati Medical Center, Metro Manila, Philippines

Victoria Dimacali

Pediatric Eye Center of Greece, Thessaloniki, Greece

Athina Kozei & Nikolaos Kozeis

School of Pharmacology, University of Nicosia, Nicosia, Cyprus

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Dimacali, V., Balidis, M., Adamopoulou, A. et al. A Case of Early Keratoconus Associated with Eye Rubbing in a Young Child. Ophthalmol Ther 9 , 667–676 (2020). https://doi.org/10.1007/s40123-020-00264-8

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Received : 03 December 2019

Published : 15 June 2020

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DOI : https://doi.org/10.1007/s40123-020-00264-8

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Keratoconus and Personality Traits: A Case-Control Study

Affiliations.

• 1 Ophthalmology Unit, Department of Experimental Medicine, University of Rome Tor Vergata, Rome, Italy.
• 2 Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL; and.
• 3 Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
• PMID: 37018764
• DOI: 10.1097/ICO.0000000000003284

Purpose: The aim of this study was to delineate the personality traits of patients affected by keratoconus (KC) compared with a group of nonkeratoconic controls matched in age and sex.

Methods: In this prospective interventional case-control study, 60 consecutive subjects (30 KC cases and 30 healthy controls), aged 18 to 30, were enrolled at the time of their first encounter at the ophthalmology unit of the Fondazione Policlinico "Tor Vergata", Roma. After completing the ophthalmic evaluation, participants were asked to respond to the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25). A complete psychiatric assessment was performed, including the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (SCID-5); the Symptom Check List-90-Revised (SCL-90); the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego-Modified (TEMPS-M); and the NEO Five-Factor Inventory (NEO-FFI).

Results: Cases had lower quality of life than controls, as demonstrated by lower scores in all NEI VFQ-25 subdomains. Nine patients with KC (30.0%) were diagnosed by the SCID-5 with at least 1 cluster C personality disorder, resulting in a 9-fold increased risk compared with controls. Moreover, keratoconic patients showed a more pronounced psychosomatic symptomatology (SCL-90) and a characteristic neurotic temperament (TEMPS-M and NEO-FFI).

Conclusions: Our results support the hypothesis that subjects with KC feature dysfunctional coping mechanisms and personality traits, which might already be present at the first clinical encounter. Ophthalmologists should question the mental and emotional status of patients with KC and be especially careful in managing these patients.

Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.

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Conflict of interest statement

The authors have no funding or conflicts of interest to disclose.

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Trends, Challenges and Controversies in Keratoconus

Get updated on the latest discourse on this increasingly relevant topic..

By Brian Chou, OD, and Jerome Legerton, OD, MS, MBA

is our annual diagnostic skills and techniques issue. In each article, eyecare experts offer practical tips and advice to help you brush up on exam techniques that you can put to use  everyday in your office. As it stands, relatively few patients are diagnosed with keratoconus in the modal eyecare practice, even though we now know the disease is far more prevalent than previously thought. New technologies allow for earlier and more frequent diagnosis. Given there are now enhanced treatment alternatives, including modern scleral contact lenses and corneal crosslinking (CXL), early detection represents an imperative. With such advances come new trends, challenges and controversies. Here, we investigate five in particular. Early Identification an Imperative A prompt diagnosis during adolescence is more important than ever because this is the critical time when CXL has the strongest indication to prevent the most progression. In contrast, if a patient already displays Munson’s sign with a spectacle-corrected visual acuity (VA) of count fingers, a surgeon may feel these eyes are beyond the time to benefit from CXL ( Figure 1 ). This would be analogous to how, in myopia management, it is valuable to initiate low-dose atropine therapy or peripheral defocus optical correction for a child with -1.00D myopia yet perhaps not so much for an adult with -12.00D myopia. Testing for genetic risk of keratoconus was commercially introduced in February of 2020 and marketed as an important method to gain early diagnostic certainty. Genetic testing has not yet achieved widespread clinical acceptance as a useful standalone predictive test. 1  Instead, tried-and-true clinical metrics continue as the basis for clinician keratoconus diagnoses. There may be an emerging role for data analytics and artificial intelligence in improving a clinician’s ability to diagnose keratoconus. In the past, various indices were proposed to aid in this capacity, including the KISA% index based on corneal topography. 2  Today with improved computational technologies, a neural network could be trained with databases of clinical metrics of those with and without keratoconus. The metrics could include best-spectacle corrected VA, intraocular pressure, corneal hysteresis, corneal thickness, corneal topography or tomography, aberrometry and pachymetry, as well as demographic data including age, race, family history of keratoconus, history of eye itching with severity and laterality, presence of allergy, asthma and eczema. A data-driven risk assessment of keratoconus may prove more sensitive and specific than that of an average clinician. Even so, the entry burden of multiple data fields may make real-time diagnosis using data analytics impractical. The greatest promise may require incorporation into electronic medical records or retrospective application to an existing patient electronic medical record database. One of the most effective pathways for new keratoconus diagnosis is through LASIK consults. Since the approval of LASIK in 1999, screening for surgical candidacy has fueled diagnosis for many new cases of keratoconus. Studies found between 6.4% to 9.6% of prospective LASIK patients were ruled as non-candidates due to probable keratoconus, whereas an estimated one in 375 in the general population are expected to have keratoconus. 3-6 Corneal topography or tomography, conducted across-the-board during LASIK consults, is arguably the single-most efficacious measurement to help a practitioner diagnose keratoconus. This unintended contribution to new keratoconus identification, however, is not optimized for early identification. Adolescents are non-candidates for LASIK, so they do not present for LASIK consultations. This prompts the question, “Should corneal topography be part of a routine comprehensive eye examination?” For early diagnosis, standard inclusion of corneal topography may be a positive step for early detection of keratoconus; even so, it is not required now for a reasonably prudent practitioner. Furthermore, none of the major vision plans require a corneal topographer to join or stay on their panels. There are forces in play that may change this, creating new incentives that should lead to improved and widespread keratoconus screening. In the meantime, early identification of keratoconus in adolescents and young adults who may progress rapidly remains a challenge. Challenge and Trend: Improving and expanding keratoconus screening. The corneal topographer is a foundational instrument for early identification, diagnosis and monitoring keratoconus rapidly and accurately, in the same manner the blood pressure cuff serves in identification, diagnosing and monitoring hypertension. Even so, not all practitioners have incorporated corneal topographers in their practices. One dynamic that may inspire movement toward adopting topography as part of routine examination is that there is now liability exposure for not diagnosing keratoconus and referring progressing disease for CXL in a timely manner. Sometime after the April 2016 FDA approval of the first CXL system, timely referral for this procedure became the standard of care for progressing keratoconus.  Today, more than 95% of commercial medical insurers provide some coverage for CXL. 7 If damage to an eye or vision loss occurs proximate to failure to diagnose and/or refer in a timely manner, the practitioner has heightened exposure to claims of negligence. The mere fact that medicolegal claims of this nature already exist foreshadows increasing practitioner medicolegal liability when not diagnosing keratoconus in a timely manner. Incorporating corneal topography as part of routine examination can mitigate this risk by improving the practitioner’s ability to diagnose and monitor keratoconus. One large vision provider network has already incorporated instrumentation, combining topography and wavefront aberrometry as a routine element of their comprehensive eye examination. 8 Combined corneal topography and aberrometry is expected to have greater power in diagnosing keratoconus than corneal topography alone. Other factors driving increased keratoconus screening include heightened public awareness and patients’ desire to be screened. Over the past decade, professional sports stars, including NBA great Steph Curry and MLB outfielder Tommy Pham, have openly discussed and raised public recognition of keratoconus. 9,10 Perhaps someday patients will commonly ask if their eye exam detects keratoconus in the same manner they ask if they have cataract, glaucoma or macular degeneration. Finally, there is a possibility that a judicial ruling establishes topography as part of the comprehensive eye exam. This would be similar to the 1974 Helling v. Carey case, in which the Supreme Court of Washington held that tonometry was a necessary part of the routine eye exam not only for patients age 40 and older, but for all. 11 However, most practitioners might prefer that their industry generate clinical care guidelines rather than leaving it to a judge or legislative body without clinical understanding and experience. Controversy:  Is concern about  progression overstated. It is well understood that keratoconus is expected to progress during adolescence to early twenties. This warrants the attention of all clinicians to ensure a timely referral for CXL to arrest disease progression. Yet for a keratoconus patient who has reached presbyopia and beyond, is concern for progression warranted and is there a concomitant over-referral for CXL? Keratoconus is understood to stabilize and arrest on its own by the third to fourth decade of life. 12 Although keratoconus can have a later onset, the probability of late onset keratoconus is low. Cases of late onset keratoconus may in fact represent pre-existing disease that was not identified sooner ( Figure 2 ). In some cases, corneal gas permeable (GP) contact lens wear may mask the diagnosis of keratoconus by confounding the topographical pattern through epithelial redistribution. If a corneal GP washout is not complete, the change in topographical appearance may masquerade as progressing keratoconus, whereas the cornea may, in fact, be returning to its natural shape. Diagnosis of keratoconus later in life may correlate with milder and stable corneal distortion. Form fruste disease may escape detection due to the lack of suspicious findings. By the time classic clinical signs of keratoconus are detectable—Munson’s sign, Vogt’s striae and Fleischer rings—the keratoconus has existed for years. It is expected that a significant number of keratoconus patients diagnosed using these classic clinical signs may already have achieved stability. With today’s emphasis on carefully monitoring for progressive corneal distortion, it is reasonable to wonder if CXL is worthwhile when the keratoconus may have stabilized on its own. Unnecessary CXL may represent an alpha risk of increased health care cost and complications from the CXL vs. beta risk of progression by a failed prognostication of nonprogression.  Standard epi-off CXL is not without its risks, with one paper citing a complication rate of between 1% to 10%. 13 A large-scale review of 2,025 eyes undergoing accelerated CXL found haze formation in 9.1% in the early postoperative period and failure of treatment in 4.2% in the late period, with other common complications including loss of two or more Snellen lines in 2.4% and delayed epithelial healing in 1.8%. 14 There are also rare reports of corneal melting and perforation after CXL. 15  Even with this understanding of complication risk, practitioners and patients with keratoconus may take comfort in knowing that the overall rate of corneal transplantation has already plummeted by fivefold with the success of scleral contact lenses. 16 Inducing fear during the counseling of keratoconus patients who are beyond their 40s to stimulate them to believe they may progress to corneal transplantation and that CXL prevents corneal transplantation may present an alpha risk for the patients that is not reasonable. A conservative approach for these seemingly late onset cases may include serial monitoring to confirm stability.  A standard of care is suggested for the intentional use of CXL that is moderated by age of onset and clinical metrics to support progression or the lack thereof, rather than an across-the-board application of CXL for all that are newly diagnosed. The personalized recommendation for intentional CXL would strike a balance between alpha and beta risk. Corneal Crosslinking or Contact Lens Treatment First? For a newly diagnosed patient with keratoconus and poor best spectacle-corrected VA, is the first order treatment CXL or contact lens prescribing? There is no practitioner consensus yet; rather, the treatment plan is managed on a case-by-case basis with differences from one practitioner to another. It is reasonable to pursue both concurrently for many keratoconus patients since CXL is not expected to normalize the shape of the cornea sufficiently to reduce the higher order aberrations that impact best spectacle-corrected VA. It is worth noting that medical insurance coverage for CXL may take months to even over a year to obtain, depending on administrative burden and criteria needed to demonstrate to the third-party payer to establish progression. It is advantageous that during this time, the patient benefits from vision improvement via contact lens prescribing and gains proficiency with lens handling. These adolescent patients need vision correction to perform well in the classroom and on the sports field. In lieu of being held in limbo waiting for the CXL approval, the patient benefits from contact lens wearing and the restoration of their visual performance immediately. Practitioners report that most patients in sclerals prior to CXL can wear the same lenses following surgical recovery. This observation suggests that it is reasonable to expect that contact lens re-prescribing may not be required after CXL. Keratoconus patients on some vision care plans should know that undergoing CXL can potentially reduce their corneal powers below the threshold for reimbursement. 17 One major plan sets a 53.00D steep keratometry criteria for the stepped-up necessary contact lens reimbursement for scleral prescribing. In the event of a reduced post-surgical steep keratometry meridian power, these patients may receive a surprise bill for out-of-pocket costs for subsequent scleral lens prescribing. At the same time, the same patient may enjoy peace of mind by minimizing the risk of disease progression. To avoid this coverage issue, initiating contact lens prescribing before CXL may be financially advantageous for the patient who may be teetering close to the third-party vision plan threshold for scleral lens reimbursement. A practitioner prescribing contact lenses before CXL should know that corneal gas permeable lenses or hybrid contact lenses may confound the surgeon’s ability to assess the pre-treatment topography and the post treatment progression. Soft lenses and sclerals impact corneal shape less and are expected to cause less interference with topographical and tomographic evaluation for disease progression. Challenge and  Emerging Trend:  Wavefront-guided  contact lenses. Retrospective medical records review and prospective predictions conclude that custom soft lenses may be the lens of choice for sizeable number with keratoconus. 18 Presently, custom soft contact lenses indicated for keratoconus have increased thickness and deliver oxygen transmissibility below the Holden-Mertz criteria for daily wear. They are lathe cut and have a high cost of goods, making disposability infeasible. New ultrahigh Dk lens materials and molding methods may deliver higher oxygen transmissibility along with reduced cost of goods that might allow a monthly disposable modality ( Figure 3 ).  Also keep in mind that increased adoption of aberrometers by eyecare practitioners and software for converting simultaneous aberrometry and registration data to lens manufacturing is enabling wavefront-guided scleral contact lenses and custom soft lenses that manage the higher order aberrations that commonly reduce VA in keratoconus ( Figure 4 ). The ultimate achievement of improved best corrected contact lens VA is anticipated. Over the past 25 years, keratoconus treatment has advanced tremendously. While corneal gas permeable contact lenses and penetrating keratoplasty have ongoing roles for long-term keratoconus management, their frequency of use is muted today. This is largely due to the dramatic success of scleral lenses in restoring vision and collagen crosslinking in minimizing disease progression. New custom wavefront-guided soft lenses for keratoconus may emerge as a viable alternative for mild to moderate keratoconus.  Unfortunately, the greatest challenge from a public health perspective is that far too many adolescents and young adults with keratoconus remain undiagnosed, and there remains a cohort with known keratoconus who have not yet received the optimized treatment available today.  Dr. Chou practices at ReVision Optometry, a referral clinic for keratoconus and scleral lenses in San Diego. He reported the first US case of Intacs for keratoconus and is a past recipient of the National Keratoconus Foundation’s Top Doctor award. He has no relevant financial interests to disclose. Dr. Legerton is the co-founder of SynergEyes, Innovega, Prolign Technologies and Ocular Surface Innovations. He is an inventor of more than 200 US and international patent cases and is honored with the American Optometric Association Outstanding Achievement Award, the American Academy of Optometry Founders’ Award, the Contact Lens Manufacturers Association Trailblazers Award and the Orthokeratology Academy of America Achievement Award.  1. Cole J. KCN genetic testing: where does it fit in? RCCL. 2022;159(1):10-3. 2. Rabinowitz YS, Rasheed K. KISA% index: a quantitative videokeratography algorithm embodying minimal topographic criteria for diagnosing keratoconus. J Cataract Refract Surg. 1999;25(10):1327-35. 3. Xu K, McKee HD, Jhanji V. Changing perspective of reasons for not performing laser-assisted in situ keratomileusis among candidates in a university eye clinic. Clin Exp Optom. 2013;96(1):20-4. 4. Sharma N, Singhvi A, Sinha R, Vajpayee RB. Reasons for not performing LASIK in refractive surgery candidates. J Refract Surg. 2005;21(5):496-8. 5. Hori-Komai Y, Toda I, Asano-Kato N, Tsubota K. Reasons for not performing refractive surgery. J Cataract Refract Surg. 2002;28(5):795-7. 6. Godefrooij DA, de Wit GA, Uiterwaal CS, Imhof SM, Wisse RP. Age-specific incidence and prevalence of keratoconus: a nationwide registration study. Am J Ophthalmol. 2017;175:169-72. 7. Insurance coverage for iLink corneal crosslinking. Glaukos. . Accessed January 17, 2023.  8. Clarifye: the digital eye exam that gives more information. LensCrafters. . Accessed January 17, 2023.   9. Horsting L. Steph Curry, the NBA’s greatest shooter ever, has had vision problems his whole career. WarriorsWire. . April 3, 2019. Accessed January 17, 2023.  10. Kolakowski R. Rays’ Tommy Pham shares story of eye condition that threatened career. Tampa Bay Times. . October 16, 2019. Accessed January 17, 2023.  11. Ruskiewicz JP, Godio L, Myrowitz E, France L. Cost and quality implications of changes in tonometry use by optometrists. J Am Optom Assoc. 1983;54(4):339-44. 12. Gordon-Shaag A, Millodot M, Shneor E, Liu Y. The genetic and environmental factors for keratoconus. Biomed Res Int. 2015;2015:795738. 13. Seiler TG, Schmidinger G, Fischinger I, et al. Komplikationen der vernetzung der hornhaut [Complications of corneal cross-linking]. Ophthalmologe. 2013;110(7):639-44. German.  14. Çakmak S, Sucu ME, Yildirim Y, et al. Complications of accelerated corneal collagen crosslinking: review of 2,025 eyes. Int Ophthalmol. 2020;40(12):3269-77. 15. Tillmann A, Kampik D, Borrelli M, et al. Acute corneal melt and perforation—a possible complication after riboflavin/UV-A crosslinking (CXL) in keratoconus. Am J Ophthalmol Case Rep. 2022;28:101705. 16. Ling JJ, Mian SI, Stein JD, et al. Impact of scleral contact lens use on the rate of corneal transplantation for keratoconus. Cornea. 2021;40(1):39-42. 17. Chou B. New tools to tame keratoconus. RevOptom. 2019;156(4):42-9. 18. Gelles JD. Contact lenses for visual rehabilitation in keratoconus: characteristics and outcomes of contact lenses for keratoconus an evidence-based fitting algorithm. Presented at Global Specialty Lens Symposium 2020.  Related Content Imaging Tech Reveals Early Fuchs’ Dystrophy The Role of Toric Peripheries Most Informative Keratoconus YouTube Videos Least Popular Corneal Plus Conjunctival Staining Most Definitive for DED Diagnosis Advances in Endothelial Surgery: An Update for ODs Current Issue Table of Contents Read digital edition, read pdf edition, subscriptions, related topics. Contact Lenses and Solutions Copyright © 2024 Jobson Medical Information LLC unless otherwise noted. All rights reserved. Reproduction in whole or in part without permission is prohibited. Keratoconus Clinical Presentation Author: Karen K Yeung, OD, FAAO; Chief Editor: Hampton Roy, Sr, MD  more... Sections Keratoconus Practice Essentials Pathophysiology Mortality/Morbidity Patient Education Complications Laboratory Studies Imaging Studies Histologic Findings Medical Care Surgical Care Consultations Long-Term Monitoring Medication Summary Photoenhancers Antihistamines/Mast cell stabilizer, ophthalmic Mast cell stabilizers Second generation antihistamines Corticosteroids Hyperosmolar diuretics Immunomodulators Media Gallery KC generally presents in the early 20's to 30's, though patients can develop KC much earlier or later in years. Patients with keratoconus often report decreasing vision (distortions, glare/flare, and monocular diplopia or ghost images), with multiple unsatisfactory attempts in obtaining optimum spectacle correction. Soft contact lenses and spectacles may initially give satisfactory vision, but vision tends to decline over time and requires rigid gas-permeable contact lenses for correction. Other contact lens options include piggyback lens systems (usually a gas-permeable lens over a soft, perhaps silicone hydrogel, lens), hybrid lenses (eg, Synergeyes TM) and, increasingly over the past decade, gas-permeable scleral lenses. [ 21 , 32 ] Keratoconus is differentiated into mild, moderate, and advanced disease, as well as by shape. Mild keratoconus External and corneal signs are often absent or minimal. A history of multiple inadequate spectacle corrections of one or both eyes may be noted and may include oblique astigmatism on refraction as well as moderate-to-high myopia. Irregularly astigmatic keratometry values (egg-shaped), not necessarily on the steep side of normal (approximately 45 D), are consistent with diagnosis. Diagnosis can be confirmed with corneal topography or tomography, which may reveal inferior corneal steepening (approximately 80% of keratoconus cases), central corneal astigmatic steepening (approximately 15% of keratoconus cases), or even bilateral temporal steepening (extremely rare). Corneal tomography shows paraxial corneal thinning. Corneal sensitivity and tear secretion are decreased. [ 33 ] Moderate keratoconus    [ 22 ] One or more corneal signs of keratoconus are often present, as follows: Enhanced appearance of the corneal nerves is noted. Approximately 40% of eyes in patients with moderate keratoconus develop Vogt striae (fine-stress lines) in the deep stroma. Approximately 50% develop Fleischer ring, a deposition of iron in the basal epithelial cells in a (often partial) ring shape at the base of the conical protrusion. Approximately 20% develop corneal scarring. Superficial corneal scarring can be fibular, nebular or nodular. Deep stromal scarring may occur, perhaps representing resolved mini-hydrops events. Some patients show scarring at the level of the Descemet membrane (posterior limiting lamina), consistent in appearance with posterior polymorphous corneal dystrophy. This may be a posterior polymorphous corneal dystrophy variant. [ 34 ] Paraxial (usually inferior to the pupil) stromal thinning may be appreciated. Keratometry values typically increase to 45-52 D. Distortion of the retinoscopy and direct ophthalmoscope red pupillary reflex may allow observation of "scissoring" or an inferior distortion termed the oil drop sign. The Munson sign is noted when, upon downgaze, a "V" shape is visible in the cornea's profile against the lower lid margin. This is the accentuation of the conical shape of the modest to advanced keratoconus cornea. Advanced keratoconus Keratometry values are greater than 52 D. Enhancement of all corneal signs, symptoms, and visual loss/distortion, including Vogt striae, Fleischer ring, and/or scarring, is present. Acute corneal hydrops may occur. Shape-based differentiation Keratoconic eyes can also be divided by their shape. Nipple cones have a diameter of 5 mm or less and are located in the center or slightly below the center of the cornea. Oval cones are larger in diameter and reside inferonasally or inferotemporally to the center of the cornea. Globus cones involve approximately 75% of the cornea and are the least common. Although not definitively identified, genetic inheritance, systemic and ocular associations, eye rubbing, atopy and specifically ocular allergies, and contact lens wear are proposed risk factors. [ 35 , 36 ] Several reports suggest, perhaps coincidentally, associations with keratoconus and other corneal dystrophies. Advanced keratoconus rarely progresses to acute corneal hydrops (acute keratoconus), wherein breaks occur in the Descemet layer that lead to central stromal edema and secondary severe corneal scarring. Patients report a sudden loss of vision and some ocular discomfort or pain in one eye but usually not much conjunctival injection. Acute treatment of hydrops is palliative; many corneas flatten secondary to hydrops, and both visual acuity and contact lens application may rarely improve following such events. If secondary scarring is severe and central, corneal transplantation (ie, PKP) may be warranted. Patients with keratoconus develop all complications of contact lens wear, especially abrasion [ 37 ] and giant papillary conjunctivitis. Contact lens–related secondary giant papillary conjunctivitis may be treated with topical mast cell stabilizers, antihistamine, and, occasionally, steroid drops. Wisse RP, Kuiper JJ, Gans R, Imhof S, Radstake TR, Van der Lelij A. 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Corneal collagen cross-linking: a review of 1-year outcomes. Eye Contact Lens . 2014 Nov. 40 (6):345-52. [QxMD MEDLINE Link] . Tuft SJ, Hassan H, George S, Frazer DG, Willoughby CE, Liskova P. Keratoconus in 18 pairs of twins. Acta Ophthalmol . 2012 Sep. 90(6):e482-6. [QxMD MEDLINE Link] . Farjadnia M, Naderan M. Corneal cross-linking treatment of keratoconus. Oman J Ophthalmol . 2015 May-Aug. 8 (2):86-91. [QxMD MEDLINE Link] . Georgiou T, Funnell CL, Cassels-Brown A, O'Conor R. Influence of ethnic origin on the incidence of keratoconus and associated atopic disease in Asians and white patients. Eye (Lond) . 2004 Apr. 18(4):379-83. [QxMD MEDLINE Link] . Alió JL, Shabayek MH. Corneal higher order aberrations: a method to grade keratoconus. J Refract Surg . 2006 Jun. 22(6):539-45. [QxMD MEDLINE Link] . American Academy of Ophthalmology 2013 Annual Meeting. Presented November 16, 2013. Colin J, Malet FJ. Intacs for the correction of keratoconus: two-year follow-up. J Cataract Refract Surg . 2007 Jan. 33(1):69-74. [QxMD MEDLINE Link] . Fontana L, Parente G, Tassinari G. Clinical outcomes after deep anterior lamellar keratoplasty using the big-bubble technique in patients with keratoconus. Am J Ophthalmol . 2007 Jan. 143(1):117-124. [QxMD MEDLINE Link] . Goodman A. Crosslinking safe in children, adolescents with keratoconus. Medscape Medical News. November 28, 2013. Available at https://www.medscape.com/viewarticle/815184 . Accessed: December 7, 2013. Jafri B, Li X, Yang H, Rabinowitz YS. Higher order wavefront aberrations and topography in early and suspected keratoconus. J Refract Surg . 2007 Oct. 23(8):774-81. [QxMD MEDLINE Link] . Kelly TL, Williams KA, Coster DJ. Corneal transplantation for keratoconus: a registry study. Arch Ophthalmol . 2011 Jun. 129(6):691-7. [QxMD MEDLINE Link] . Kosaki R, Maeda N, Bessho K, Hori Y, Nishida K, Suzaki A. Magnitude and orientation of Zernike terms in patients with keratoconus. Invest Ophthalmol Vis Sci . 2007 Jul. 48(7):3062-8. [QxMD MEDLINE Link] . Rabinowitz YS. Intacs for keratoconus. Curr Opin Ophthalmol . 2007 Jul. 18(4):279-83. [QxMD MEDLINE Link] . Raiskup-Wolf F, Hoyer A, Spoerl E, Pillunat LE. Collagen crosslinking with riboflavin and ultraviolet-A light in keratoconus: long-term results. J Cataract Refract Surg . 2008 May. 34(5):796-801. [QxMD MEDLINE Link] . Schlegel Z, Hoang-Xuan T, Gatinel D. Comparison of and correlation between anterior and posterior corneal elevation maps in normal eyes and keratoconus-suspect eyes. J Cataract Refract Surg . 2008 May. 34(5):789-95. [QxMD MEDLINE Link] . Shimmura S, Tsubota K. Deep anterior lamellar keratoplasty. Curr Opin Ophthalmol . 2006 Aug. 17(4):349-55. [QxMD MEDLINE Link] . Sorbara L, Dalton K. The use of video-keratoscopy in predicting contact lens parameters for keratoconic fitting. Cont Lens Anterior Eye . 2010 Jun. 33(3):112-8. [QxMD MEDLINE Link] . Nattis A, Donnenfeld ED, Rosenberg E, Perry HD. Visual and keratometric outcomes of keratoconus patients after sequential corneal crosslinking and topography-guided surface ablation: Early United States experience. J Cataract Refract Surg . 2018 Aug. 44 (8):1003-1011. [QxMD MEDLINE Link] . An optic section of a keratoconic cornea shows corneal thinning. Vogt striae and some scarring can also be seen centrally; superiorly, a small (brown) section of the Fleischer ring is noted. The fluorescein pattern of a rather flat-fitted rigid contact lens on an advanced keratoconic cornea. Contributor Information and Disclosures Karen K Yeung, OD, FAAO Senior Optometrist, UCLA Arthur Ashe Student Health and Wellness Center; Clinical Assistant Professor, College of Optometry, Western University of Health Sciences Karen K Yeung, OD, FAAO is a member of the following medical societies: American Academy of Optometry Disclosure: Nothing to disclose. Barry A Weissman, OD, PhD, FAAO Retired Professor of Optometry, Southern California College of Optometry at Marshall B Ketchum University; Professor Emeritus of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine Barry A Weissman, OD, PhD, FAAO is a member of the following medical societies: American Academy of Optometry , American Optometric Association , California Optometric Society , International Society for Contact Lens Research Disclosure: Nothing to disclose. Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference Disclosure: Received salary from Medscape for employment. for: Medscape. Christopher J Rapuano, MD Professor, Department of Ophthalmology, Sidney Kimmel Medical College of Thomas Jefferson University; Director of the Cornea Service, Wills Eye Hospital Christopher J Rapuano, MD is a member of the following medical societies: American Academy of Ophthalmology , American Ophthalmological Society , American Society of Cataract and Refractive Surgery , Contact Lens Association of Ophthalmologists , Cornea Society , Eye Bank Association of America , International Society of Refractive Surgery Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: AAO; OMIC; American Society of Ophthalmic Trauma (ASOT); Avellino, Baxis; Bio-Tissue; Celularity; Dompe; Emmecell; Glaukos; Kala; Oyster Point; Tarsus; TearLab<br/>Serve(d) as a speaker or a member of a speakers bureau for: Dompe<br/>Received research grant from: Glaukos<br/>Received income in an amount equal to or greater than $250 from: AAO; OMIC; Baxis; Bio-Tissue; Cellularity; Dompe; Glaukos; Kala; TearLab<br/>stock options for: RPS, Fount Bio. Hampton Roy, Sr, MD † Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology , American College of Surgeons , Pan-American Association of Ophthalmology Disclosure: Nothing to disclose. Fernando H Murillo-Lopez, MD Senior Surgeon, Unidad Privada de Oftalmologia CEMES Fernando H Murillo-Lopez, MD is a member of the following medical societies: American Academy of Ophthalmology Disclosure: Nothing to disclose. What would you like to print? Print this section Print the entire contents of Print the entire contents of article Anterior Segment and Fundus Photography Postoperative Corneal Edema Peters Anomaly Fast Five Quiz: Are You Familiar With Dry Eye Disease? Corneal Abrasion Fast Five Quiz: Ocular Rosacea Elevated Estradiol Linked to Bulging Cornea in Premenopausal Women Optimal Management of Perianal Disease in Crohn's Disease: The Importance of a Multidisciplinary Approach Don't Overlook Bone Health in Coeliac Disease Cornea and External Disease Artificial Intelligence and Corneal Diseases Perioperative Care of the Patient With eye Pathologies Undergoing Nonocular Surgery Drug Interaction Checker Pill Identifier Calculators 2001/recap/977957 Highlights in Corneal Disorders From AAO 2022 2003/viewarticle/do-statins-have-effect-severe-disease-people-noncirrhotic-2023a1000d20education Do Statins Have an Effect on Severe Disease in People With Noncirrhotic Chronic Liver Disease? 0.25 LOC / CME / MOC Credit / CE Credits education You are being redirected to Medscape Education Yes, take me there 0.25 LOC / CME / MOC Credit / CE Do Statins Have an Effect on Severe Disease in People With Noncirrhotic Chronic Liver Disease? 2001/recap/994224 Key Data in Corneal Disorders From AAO 2023 2001/s/viewarticle/987848 FDA Says India-Made Eye Drop Linked to Some Infections, Blindness and One Death An official website of the United States government The .gov means it’s official. 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Advanced Search Journal List v.34(12); 2020 Dec Language: English | Chinese Current perspectives in the management of keratoconus with contact lenses 1 Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore, 168751 Singapore 2 Singapore Eye Research Institute, 20 College Road Discovery Tower Level 6, The Academia, Singapore, 169856 Singapore 3 Duke-NUS Medical School, 8 College Road, Singapore, 169857 Singapore Elizabeth Wen Ling Lim 4 Yong Loo Lin School of Medicine, National University of Singapore, 1E Kent Ridge Road, Singapore, 119228 Singapore Our aim is to review current and significant articles on contact lens wear in keratoconus patients. A comprehensive literature search of PubMed was performed for the following topics on contact lens wear in keratoconus patients: (1) characteristics of contact lens wearers, (2) safety and efficacy, (3) complications, (4) fitting techniques, (5) contact lens wear after procedures/surgeries, (6) patient satisfaction. A total of 104 studies were finally selected and reviewed. Gas permeable (GP) lens wear provided significantly better vision than glasses. Special cone design lenses had better patient comfort levels though there was no difference in best corrected visual acuity among the GP lenses. Soft lenses showed good efficacy for the treatment of mild-to-moderate keratoconus with newer designs improving visual performance such as customised hydrogel and novel pinhole lenses. Scleral and hybrid lenses provide good visual acuity and comfort for keratoconic patients previously intolerant to RGP lenses. RGP lens wear post-cross linking (CXL) is relatively well-tolerated. Contact lenses may still be required post intrastromal corneal ring procedures and post keratoplasty. Scheimpflug imaging and anterior segment optical coherent tomography (ASOCT) are useful in contact lens fitting. Computerized contact lens fitting techniques could reduce the chair time of lens fitting as well as improve comfort and visual performance. Contact lenses play an important role in the visual rehabilitation of keratoconus patients. New contact lens designs and materials have significantly expanded the available fitting options for keratoconus patients. Imaging technology can be utilized to guide contact lens fitting. 摘要 当前关于接触镜治疗圆锥角膜的观点 本文旨在对圆锥角膜患者佩戴角膜接触镜的重要文献进行回顾。我们于PubMed进行了全面的文献检索, 聚焦于圆锥角膜患者佩戴接触镜的问题: (1) 接触镜佩戴者的特点 (2) 安全性和有效性 (3) 并发症 (4) 适配技术 (5) 手术后的接触镜的佩戴 (6) 患者满意度。文中最终纳入并回顾了104项研究。 佩戴透气性 (Gas permeable, GP) 镜片比眼镜具有更好的视野。特殊设计的锥形镜片使病人拥有更佳的舒适度, 尽管最佳矫正视力与GP镜片之间并没有差异。软性镜片在治疗轻中度圆锥角膜方面显示出良好疗效, 新设计的如定制水凝胶和新型针孔镜片改善了视觉性能。巩膜和混合镜片为不能耐受RGP镜片的圆锥角膜患者提供了良好的视力和舒适度。佩戴RGP镜片后交联 (post-cross linking, CXL) 相对耐受性较好。角膜基质环术和角膜成形术后仍需佩戴接触镜。 Scheimpflug成像和眼前节光学相干断层扫描 (anterior segment optical coherent tomography, ASOCT) 有助于接触镜的适配。计算机化的接触镜适配技术可以减少镜片配戴的占用时间, 提高舒适度和视觉性能。 角膜接触镜在圆锥角膜患者的视觉康复中起着重要作用。新接触镜的设计和材料极大地扩展了圆锥角膜患者可用的适配选择。成像技术的利用有助于指导接触镜的配戴。 Introduction Keratoconus is a progressive noninflammatory ectatic disorder of the cornea characterized by thinning and protrusion of the cornea leading to irregular astigmatism, myopia and poor vision [ 1 ]. It is the most common corneal ectatic condition with a prevalence of about 54 per 100,000 people in the United States [ 2 ]. A more recent nation-wide study performed in the Netherlands showed that the estimated prevalence of keratoconus in the general population is 1:375 (265 cases per 100,000, 95% CI: 260–270) which are five to ten times higher than previously reported values in population studies [ 3 ]. The mean age at diagnosis is 28.3 years with 60.6% of patients being male [ 3 ]. Risk factors include both genetic and environmental factors such as eye rubbing, personal history of atopy, and family history of keratoconus [ 4 ]. Due to its chronic and debilitating nature, keratoconus has a significant impact on vision-related quality of life (VRQoL) [ 5 ]. Hence the management of keratoconus patients involves long term care with the need for nonsurgical and surgical management options. The corneal ectasia preferred practice pattern by the American Academy of Ophthalmology contains useful clinical guidelines for the overall management (nonsurgical and surgical) of keratoconus [ 6 ]. In the early stages of keratoconus, the vision could be corrected with glasses. However, in the moderate to advanced stages, spectacles play a limited role and contact lenses may be required for vision correction [ 7 ]. The global consensus on keratoconus and ectatic diseases recognized the importance of contact lenses in the visual rehabilitation of these patients. They recommend that rigid contact lenses be used in cases of unsatisfactory vision with glasses or conventional soft contact lenses (SCLs). In a patient who has failed a trial of corneal gas permeable (GP) lenses, the alternative contact lens options include hybrid (rigid center, soft skirt), toric, bitoric, keratoconus design SCLs, keratoconus design corneal GP contact lenses, piggy-back, corneoscleral, miniscleral, and scleral lenses [ 8 ]. The recent U.S. Food and Drug Administration approval of corneal cross-lining (CXL) provides an option that may slow or halt the progression of keratoconus. In recent years, there have been advances in the surgical management of keratoconus with surgical procedures such as CXL, topography guided excimer laser treatment combined with CXL, intrastromal corneal ring procedures performed alone or in combination with CXL, intraocular contact lenses performed alone or in combination with CXL, and anterior lamellar keratoplasty procedures. While these procedures have resulted in better visual outcomes, contact lens wear may still be required in postoperative visual rehabilitation. With recent developments in contact lens properties and design, a greater range of contact lens options are available for patients with corneal irregularities. These options include larger diameter GP lenses, scleral lenses, hybrid lenses, and custom soft lenses. The ultimate aim is to optimise visual outcomes, patient satisfaction, and comfort for keratoconus patients using contact lenses. The benefits of new and more comfortable contact lens designs, combined with CXL’s effect on progression, should continue to reduce the number of individuals needing some form of keratoplasty procedure. The purpose of this paper is to provide a review of current and significant articles focusing on the safety and efficacy of contact lenses in the visual rehabilitation of keratoconus. A comprehensive literature search of PubMed, an electronic database, was performed up to 17th February 2019. The keywords used were: “contact lens”, “rigid contact lens”, “rigid gas permeable”, “RGP”, “Rose K contact lens”, “soft contact lens”, “scleral contact lens”, “miniscleral contact lens”, “piggyback contact lens”, “prosthetic contact lens”, “PROSE”, “hybrid contact lens”, “eye print pro”, “keratoconus”, “KC”, “corneal ectasia”, “ectasia”, “Scheimpflug”, “anterior segment optical coherence tomography”, and “ASOCT”. Using this method, 699 search results were generated. The references of retrieved articles were also searched for other relevant articles. Publications in English on the following topics on contact lens wear in keratoconus patients were included in our review: (1) characteristics and survey of contact lens wearers, (2) safety and efficacy, (3) complications, (4) fitting techniques, (5) contact lens wear after cross-linking, intracorneal ring segment insertion or penetrating keratoplasty (PK), (6) satisfaction and quality of life. Publications which did not contain information of interest were excluded. A total of 104 studies were finally selected and reviewed. In this paper, GP lenses refer to corneal GP lenses (older term RGP lenses). Results and discussion Characteristics and survey of contact lens wear in keratoconus patients. Cohort and cross-sectional studies show that the majority of keratoconus patients wearing contact lenses are fitted with corneal GP lenses. (Table ​ (Table1). All 1 ). All the different types of contact lenses mentioned in this paper have been tabulated for easy reference (Table  2 ). Characteristics and survey of contact lens wear in keratoconus patients. Authors Study design No of eyes Severity Follow-up (months) Soft contact lens GP Others Outcomes Wagner et al. [ ] Prospective cohort 1209 95% steep K ≥ 45 D 8 years NA 65% Contact lenses: 74% Spectacles: 16.1% No vision correction: 3.6% ↓ contrast sensitivity Weed et al. [ ] Prospective longitudinal 200 patients Mean steep K: 50.76 ± 4.86 D 4 years 1% 90.6% Hybrid lenses: 6.4% Scleral: 2% 93% VA ≥ 6/9 achieved with GP (90.6%) 4% required PK Bilgin et al. [ ] Retrospective longitudinal 1004 Mild: 55 (5.47%) Moderate: 547 (54.5%) Advanced: 326 (32.5%) Severe: 76 (7.6%) 6.4 ± 7.3 years NA Majority of eyes (>90%) NA successful outcomes delaying need for surgery achieved in 98.9% eyes Lim et al. [ ] Retrospective cohort 228 NA NA 0 96.1% Keratosoft/softperm: 0.8% Scleral: 0.4% 87% VA ≥ 6/9 Fatima et al. [ ] Retrospective cross-sectional 142 Mild: 20 (14.4%) Moderate: 51 (36.7%) Advanced: 45 (32.4%) Severe: 23 (16.6%) NA 0 Conventional GP:113 (79.5%) Rose K: 29 (20.4%) Boston scleral: 2 (0.1%) 91% VA ≥ 6/9, 99% VA ≥ 6/18 Shneor et al. [ ] Prospective cross-sectional 244 pts NA NA 13% 67.7% Scleral: 4.2% Corneal transplantation: 21.3% 78.7% wore CL Wei et al. [ ] Prospective cross-sectional study 129 KC patients: 53.62 D KC suspect: 45.60  D (  < 0.001) NA 8 121 (94%) NA 67% wore CL 83.3% KC eyes/100% KC suspect eyes VA > 20/40 (0.3), KC patients ↓ contrast sensitivity Rashid et al. [ ] Retrospective case review 254 pts Mild: 6.2% Moderate: 22.9% Severe: 71% NA 0 31.1% GL: 34.6% GL + GP: 32.3% PK: 16.5% NA GP gas permeable, K keratometry, D diopters, NA not applicable, PMMA polymethyl methacrylate, SGP semi gas permeable, VA visual acuity, KC keratoconus, pts patients, CL contact lens, GL glasses, PK penetrating keratoplasty. Summary and classification of all the contact lens models included in this review. Corneal GP lens Soft lens Corneo-scleral/scleral lens Hybrid lens Conventional Kerasoft IC (Ultrasound International Limited, Bedfordshire, UK) Rose K2 XL ClearKone (SynergEyes) Rose K Toris K silicone hydrogel (SiHy) MSD miniscleral SoftPerm Rose K2 Customised hydrogel Bitangential miniscleral Soper Novel pinhole soft lens (Purecon, New Delhi) Scleracon (Lenticon, Madrid, Spain) Boston Equalens II Multicurve Miniscleral RGP (ESCLERA, Mediphacos, Buritis, MG, Brazil) Boston 7 Soft (Hioxifilcon A and Lucifilcon A) Jupiter (Essilor Contact Lens Division, Dallas, Texas) CFKE PROSE (Boston Foundation for Sight, Needham Heights, MA, USA) Menicon Z EyePrintPRO (Advanced Vision Technologies, Lakewood, Colo.) YK (Lucid Co, Seoul, South Korea) Zenlens (Alden Opital/Bausch and Lomb, Kingston-upon-Thames, UK) Pancorneal toric RGP Aphex KC RGP GP gas permeable, PROSE prosthetic replacement of the ocular surface ecosystem, CFKE conflex air keratoconus 100 UV. Long-term studies (Collaborative Longitudinal Evaluation of Keratoconus (CLEK) and the Dundee University Scottish Keratoconus Study (DUSKS)) show that most patients are fitted with contact lenses when vision can no longer be corrected to at least 20/30 with glasses [ 9 , 10 ]. Longitudinal and cross-sectional studies worldwide on the characteristics and survey of contact lens wear in keratoconus patients show that GP lenses remain the mainstay treatment for keratoconus [ 11 – 16 ], with the majority of keratoconus patients attaining good visual acuity (VA) with lens wear. In the (CLEK) study looking at patients with moderate to severe keratoconus (95% had steep keratometry of >45 D), 74% of patients wore contact lenses, 16.1% wore spectacles, and 3.6% had no vision correction [ 11 , 16 ]. The CLEK population had good visual outcomes with 78% of patients achieving a best corrected visual acuity (BCVA) of 20/40 (6/12) or better in both eyes. 65% of patients wore GPs in both eyes and most of them (73%) reported that their lenses were comfortable. Most GP lenses (88%) were fitted with apical touch [ 11 , 16 ]. In the DUSKS study, contact lens wear was the mainstay of treatment (76% of 200 patients wore contact lenses) with 91% wearing GP lenses, 6% wearing hybrid contact lenses, and 2% wearing scleral lenses [ 9 ]. In another longitudinal study, due to good visual outcomes, contact lens wear delayed the need for surgery in keratoconus patients in 98.9% of eyes [ 17 ]. In a study on 130 keratoconus patients (228 eyes) in the United Kingdom, GP lenses of the spherical, elliptical and special cone lens design were used in 96.1% of eyes [ 12 ]. With contact lens wear, 87% achieved a VA of 6/9 (20/30) or better and 65% were able to wear their lenses for more than 12 h a day [ 12 ]. Another cross-sectional study in New Delhi showed similar findings with 99.9% of eyes wearing GP lenses (79.5% conventional GP, 20.4% Rose K) and 91% of eyes achieving a VA of 6/9 (20/30) or better [ 13 ]. Conventional GP lenses refer to non specialty design GP lenses. In Israel, similar results were also found in a cross-sectional study which reported that 78.7% of patients wore contact lenses (67.7% RGP, 13% soft CL, 4.2% scleral) and 21.3% of patients had undergone corneal graft surgery [ 14 ]. In Singapore, 67% of keratoconus patients wore contact lenses with 94% of them wearing GP lenses [ 15 ]. With contact lens wear, 83.3% of keratoconus eyes and 100% of keratoconus suspect eyes achieved a VA of 0.3 (decimal) (20/40). In the United Kingdom, Pullum et al. studied the characteristics of 538 patients with scleral contact lens wear over a 5-year period and found that primary corneal ectasia accounted for 61.4% of eyes [ 18 ]. Recent advances in surgical options for keratoconus include cross-linking, intracorneal rings, photorefractive keratometry, phakic intraocular lenses, and anterior lamellar keratoplasty. Although it would be important to compare the results of surgery and contact lens wear for a similar disease stage, there is currently no published literature on this subject. Contact lens efficacy and comfort Comparative studies—gp and soft/scleral/hybrid lenses. Comparative studies show that specialty design contact lenses, new design scleral lenses and hybrid lenses had better patient comfort levels than conventional GP lenses (Fig.  1 , Table ​ Table3 3 ). a Left eye Pentacam tomography: central conical pattern shown on the keratometry map. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Left eye: maximum keratometry 57.4 D; minimum keratometry 53.6 D; Rose K2 GP lens 6.30 mm BC/−8.25 D/8.7 mm Dia.). Comparative studies on contact lens efficacy and comfort (GP and soft/scleral/hybrid contact lenses). Author Study design Contact lens type No. of eyes Follow-up (months) Keratometry (D) BCLCVA (logMAR) Contrast sensitivity Wear-time (hours)/comfort Cons Gupta et al. [ ] Randomised comparative trial Rose K vs. Soper 60 3 Sim K max Rose K: 56.72 ± 4.54 Soper: 55.5 ± 3.88 Rose K: 0.06 ± 0.09 Soper: 0.09 ± 0.1 NA Rose K group had better comfort scores NA Levit et al. [ ] Randomised controlled trial Zenlens (Scleral lens) vs. Rose K 34 4 Kmax (mean): 6.2 mm (±0.60) No significant difference (  = 0.563) No significant difference (  = 0.316) SL had higher subjective comfort scores (  = 0.002) NA Kazanci et al. [ ] Comparative Rose K, Boston Equalens II, Boston 7, CFKE 229 ≥12 NA Significant ↑ VA (  < 0.05) NA Rose K: 9.7 ± 0.88; Boston Equalens II: 8.0 ± 1.39; Boston 7: 7.9 ± 1.19; CFKE: 8.7 ± 2.24 NA Fernandez-Velazquez et al. [ ] Retrospective comparative KIC and Rose K 94 KIC, 97 Rose-K ≥6 Sim K steep: 47.90 ± 3.70 (KIC), 49.00 ± 3.42 (Rose K) 0.04 ± 0.07 (KIC), 0.04 ± 0.07 (Rose K) NA 11.6 ± 1.5 (KIC), 11.1 ± 1.5 (Rose K) NA Betts et al. [ ] Case series Rose K and habitual 20 2 Steep K: 51.74 ± 4.48 (steep eye) NA Improvement 0.67 ± 1.28 points (5-point scale) 15.33 ± 2.74 (Rose K) 14.89 ± 2.76 (habitual) NA Hassani et al. [ ] Comparative GP, ClearKone SynergEyes hybrid 28 NA Mean K: 7.23 ± 0.62 (mm) ClearKone: 0.022 ± 0.03 GP: 0.057 ± 0.09 (  = 0.004) NA NA NA Carracedo et al. [ ] Comparative study ClearKone vs. habitual CL 33 1 Mean K steep: 55.11 ± 9.37 0.16 ± 0.12 (habitual) −0.006 ± 0.058 (ClearKone) 1.26 ± 0.22 (habitual) 1.65 ± 0.19 (ClearKone) (  < 0.001) VAS comfort score: 8.37 ± 1.43 (ClearKone) NA Hashemi et al. [ ] Comparative case series ClearKone-Synergeyes, GP 40 pts NA Mean K ClearKone: 48.68 ± 5.82 (R) 48.99 ± 4.28 (R) ClearKone: 0.01 ± 0.02 (R) GP: 0.02 ± 0.03 (R) (  = 0.22) NA Comfort: ClearKone > GP NA D diopter, BCLCVA best contact lens corrected visual acuity, K keratometry, max maximum, NA not applicable, VA visual acuity, KIC kerasoft IC, RGP rigid gas permeable, CL contact lens, VAS visual acuity score, R right. a Alden Opital/Bausch and Lomb, Kingston-upon-Thames, UK. Many comparative studies compared the efficacy and comfort of GP lenses with other lens types or glasses. Among GP lens types, Rose K had better patient comfort levels [ 19 , 20 ]. Most studies reported that GP lens wear provided significantly better vision and improved three-dimensional depth perception as compared with glasses though there was no difference in best contact lens corrected visual acuity (BCLCVA) among the GP lenses (Boston Equalens II, Boston 7, CFKE, Rose K, and Rose K2) [ 20 , 21 ]. There was also no difference in BCLCVA between Rose K and Kerasoft IC contact lenses for the treatment of mild-to-moderate keratoconus [ 22 ]. The study by Betts et al. reported no improvement in the VA in keratoconic patients wearing Rose K as compared with habitual lenses, though comfort levels were significantly higher, with 72% of patients stating that they preferred Rose K lenses over their habitual lenses and 87% reporting that they would continue wearing Rose K lenses [ 23 ]. A new randomized controlled study by Levit et al. compared the efficacy and comfort of Rose K and Zenlens (a Scleral lens manufactured in Boston XO2 material, Alden Optical/Bausch and Lomb, Kingston-upon-Thames, UK) [ 24 ]. It found no significant difference in VA ( P  = 0.563) or contrast sensitivity ( P  = 0.316). However, scleral lens wearers had higher subjective comfort scores ( P  = 0.002) [ 24 ]. When comparing GP/habitual lenses to hybrid lenses, visual outcome is equivocal with two studies showing that ClearKone (SynergEyes) hybrid lens wear had improved VA as compared with GP/habitual lens [ 25 , 26 ] while Hashemi et al. did not find a significant difference between these two lenses [ 27 ]. Contrast sensitivity was shown to be better in ClearKone lens wearers as compared with GP lenses [ 26 ]. Patient satisfaction and VRQoL were better in those who used ClearKone lenses [ 26 , 27 ]. Between hybrid lenses, the ClearKone lens has a better oxygen permeability at the central cornea, 2.0 mm and 4.5 mm temporal to the central cornea as compared with the SoftPerm lens as the soft lens material in ClearKone is silicone hydrogel (SiHy) compared with hydrogel material in the SoftPerm lenses [ 28 ]. SoftPerm lenses have since been discontinued in 2010 due to oxygen permeability issues. In summary, the comparative studies show that newer specialty design keratoconus GP lenses had better comfort levels than conventional or habitual GP lenses although there was no difference in the BCVA between the two groups. For mild-to-moderate keratoconus, soft keratoconus design lenses (Kerasoft IC) attained similar BCLVA to Rose K lenses with better comfort levels achieved. The new hybrid lens (ClearKone) had better patient satisfaction and VRQoL  than GP/habitual lenses. A new scleral lens design (Zenlens) was more comfortable than Rose K lens. Non-comparative studies—soft lenses Studies show that soft lenses are able to provide satisfactory vision in mild-to-moderate keratoconus (Table 4 ). Newly designed soft lenses, customized hydrogel lenses and pinhole contact lenses widen the scope of vision correction of keratoconus with soft lenses. Non-comparative studies on contact lens efficacy and comfort (soft and GP lenses). Author Study design Contact lens type No. of eyes Follow-up (months) Keratometry (D) Mean BCLCVA (logMAR) Contrast sensitivity Wear-time (hours)/comfort Cons Sultan et al. [ ] Case series Toris K soft 64 24 Km: 49.42 ± 6.47 RGP: 0.14 ± 0.16 Toris K: 0.20 ± 0.19 NA NA SPK (3), GPC (3), corneal edema (1) Katsoulos et al. [ ] Case series Customised hydrogel 8 NA NA −0.003 0.049 (50% contrast VA) NA NA Lunardi et al. [ ] Retrospective cross-sectional Bicurve, monocurve RGP 325 NA K2: 52.43 ± 8.51 0.20 ± 0.10 (  < 0.05) NA NA NA Szczotka-Flynn et al. [ ] Retrospective case series Menicon Z RGP 64 (33 KC, 31 irregular corneas) NA NA NA NA NA NA Kang et al. [ ] Case series YK CL 129 17.5 ± 13.8 Sim K max: 52.86 ± 5.13 0.79 ± 0.21 (Snellen) NA 12.1 Corneal staining/erosion Lee et al. [ ] Case series Multicurve 60 11.4 Sim Kmax: 55.8 ± 6.3 (steep eye) 48.7 ± 4.5 (flat eye) 71.6% ≥20/30 NA 11.9 NA Gumus et al. [ ] Case series Toris K soft 50 2 weeks 54.5 NA NA Comfort score: 92% NA Nejabat et al. [ ] Prospective case series RGP 156 NA Sim K2: 53.30 ± 4.70 0.036 ± 0.04 NA NA NA Kamar et al. [ ] Case series Pancorneal toric RGP 30 ≥2 NA 0.70 ± 0.18 (  = 0.007) NA NA NA Yanai et al. [ ] Retrospective case series Aphex KC RGP 29 40.9 ± 19.7 NA 0.1 NA 12.6 ± 3.2 NA Jain et al. [ ] Case report Rose K design CL 38 13 ± 3.5 Average Sim K Mod: 48.61 ± 1.24 Severe: 60.88 ± 5.31 94.7% VA ≥ 20/40 NA 94.1% 12–14 h Epithelial abrasion (2), hydrops (1) D diopter, BCLCVA best contact lens corrected visual acuity, Km mean keratometry, GP gas permeable, SPK superficial punctate keratitis, GPC giant papillary conjunctivitis, NA not applicable, VA visual acuity, KC keratoconus, CL contact lens, max maximum, mod moderate. Three non-comparative case series performed on soft lenses show good efficacy for the treatment of mild-to-moderate keratoconus. Sultan et al. showed that Toris K SiHy soft lenses are an effective alternative to GP lenses for the treatment of all grades of keratoconus (Amsler–Krumeich classification grades 1–4; mean keratometry 49.42 D), with no significant difference in BCVA with the two lenses [ 29 ]. The Toris K lenses are newly designed SiHy lenses with a toric front surface that is able to improve visual performance. Customised hydrogel contact lenses which incorporate vertical coma correction have also been found to improve both monocular and binocular visual performance in patients with mild-to-moderate keratoconus [ 30 ]. Higher order aberrations in patients with keratoconus can also be eliminated by wearing a novel pinhole soft lens (Purecon, New Delhi: 2.5 mm clear pupil, 8.3 mm base curve, 11.9 mm iris diameter, and 13 mm overall diameter) [ 31 ]. The pinhole effect is able to correct the aberropia caused by higher order aberrations such as vertical coma in patients with keratoconus. Non-comparative studies—GP lenses Case studies performed on GP lenses show that they are effective for the treatment of keratoconus and lens wear is comfortable (Table  4 ). The type of GP lens most frequently used depends on the severity of keratoconus, with monocurve GP lenses most frequently fitted in patients with mild-to-moderate keratoconus while bicurve GP lenses more frequently fitted in patients with severe and advanced keratoconus [ 32 ]. Two types of GP lenses (Menicon Z and YK) have comparable efficacy and comfort. YK lenses (Lucid Co, Seoul, Korea) are proprietary multicurve GP lenses for keratoconus. Menicon Z GP lenses are effective with an 82% success rate (as defined by VA, comfort, and corneal physiology) and a mean duration of wear of 2.5 years [ 33 ]. YK lenses have also been shown to be effective with 94.5% of eyes achieving a VA of 20/40 (6/12) or better (average VA 0.79 ± 0.21 Snellen decimal). It also has relatively high patient comfort levels, with 97.6% of eyes tolerating the contact lens with a mean wearing time of 12.1 h per day and 90.7% reporting that the lenses were comfortable [ 34 ]. In another study reported by Lee et al., YK lenses improved efficacy and comfort in keratoconus patients [ 35 ]. Overall, 71.6% of eyes achieved a VA of 20/30 or better, 94% tolerated the fitting, 85% reported complete comfort, and the mean wearing time was 11.9 h per day [ 35 ]. Non-comparative studies—scleral and hybrid lenses Fitting corneal GP lenses in advanced cases of keratoconus can be challenging as a result of lens decentration, dislocation, or discomfort. Scleral and hybrid lenses have been shown to provide good VA and comfort for keratoconic patients, some of whom were previously intolerant to RGP (Table ​ (Table5, 5 , Figs.  2 – 5 ). The advantages of scleral lenses over GP lenses are increased comfort and stability of lens wear. Scleral lenses with their large diameter allow for vaulting over the irregular and steep corneas and therefore have an increasing role in the treatment of corneal ectasia, providing another viable nonsurgical option. In general, scleral lenses are more comfortable than corneal GP lenses since there is no contact with the cornea which has more innervation than the sclera. Also, their larger diameter results in a more comfortable lens-to-lid interaction. In the recent years, newer scleral lens designs have expanded the scope of contact lens wear in keratoconus patients. The current recommendation by the Scleral Lens Education Society is to move away from using diameter classification in scleral lens nomenclature since it would not be accurate for extremely large or small eyes [ 36 ]. Instead, scleral lenses are classified based on the resting zone area of the lens on the ocular surface. Corneal lenses (Fig. ​ (Fig.1) are 1 ) are lenses which rest entirely on the cornea, corneo-scleral lenses (Figs. ​ (Figs.2 2 – 4 ) are lenses which rest partly on the cornea and partly on the sclera and scleral lenses (Fig. ​ (Fig.5) are 5 ) are lenses which rest entirely on the sclera [ 36 ]. In this paper, we will use this new classification and refer to semi-scleral lenses as corneo-scleral lenses (Table  6 ). a Left eye Pentacam tomography showing an inferior steepening pattern on keratometry map with corresponding posterior elevation on the posterior elevation map. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Refraction: −0.25/−4.00 × 105° [6/6]; Capricornia corneo-scleral lens 7.00 mm BC/−7.75 D/13.50 mm Dia [6/6]). Non-comparative studies on contact lens efficacy and comfort (scleral and hybrid lenses). Author Study design Contact lens type No. of eyes Mean follow-up (months) Keratometry (D) Mean BCLCVA (logMAR) Contrast sensitivity Wear-time (hours)/comfort Cons Romero-Jimenez et al. [ ] Case series Rose K2 XL corneo-scleral 30 6–9 Mean K: 7.24 ± 1.03 (mm) 0.09 (  < 0.001) NA 9.3 ± 2.2 Corneal/conjunctival abrasion Looi et al. [ ] Case series GP scleral 2 PMD, 1 KC NA NA VA > 6/12 in 4 eyes NA Whole day NA Baran et al. [ ] Case series PROSE 118 corneal ectasia 6 52.0 ± 8.5 0.09 ± 0.15 (  < 0.001) NA NA NA Pecego et al. [ ] Retrospective Jupiter scleral 107 (KC, astig, corneal scarring) 3–17 NA VA ≥ 20/30 in 78 eyes (73%) NA NA NA Kim et al. [ ] Retrospective case review MSD Miniscleral (diameter 15.8 mm) 38 18 ± 3.5 6.24 ± 0.54 (mm) 0.10 ± 0.11 NA 10.1 ± 2.3 Corneal injection (6) Visser et al. [ ] Case series Scleral with bitangential (nonrotationally symmetrical) periphery 213 (KC, OSD, PK, astig) 9.4 weeks NA 0.8 (Snellen) NA NA NA Otten et al. [ ] Prospective case series New bitangential miniscleral 133 (L, 45% KC) 84 days (median) NA 0.022 [median] (−0.097 to 1.301) NA 14 (median) NA Ozkurt et al. [ ] Retrospective case series SoftPerm 24 23 NA 83.3% (CL) vs. 12.5% (no CL) ≥20/40 NA NA GPC (25%) PCV (25%) Arumugam et al. [ ] Retrospective PROSE 85 irregular cornea, 68 refractive, 17 OSD 4–6 h NA 0.23 ± 0.30 (irregular corneas) 0.17 ± 0.16 (refractive) 0.44 ± 0.52 (OSD) NA NA NA Rathi et al. [ ] Retrospective case series/PMD PROSE scleral lens 20 7.25 Sim K max: 54.66 ± 6.3 0.05 ± 0.08 (  = 0.0001) NA 9.30 Hydrops (3) Montalt et al. [ ] Case series Corneoscleral 27 12 46.79 ± 4.67 0.00 ± 0.14 (  < 0.001) Total HOAs decreased by 55% 13.44 ± 2.38 NA D diopter, BCLCVA best contact lens corrected visual acuity, K keratometry, NA not applicable, GP gas permeable, PMD pellucid marginal degeneration, KC keratoconus, VA visual acuity, PROSE prosthetic replacement of the ocular surface ecosystem, astig astigmatism, OSD ocular surface disease, PK penetrating keratoplasty, L Left eye, CL contact lens, GPC giant papillary conjunctivitis, PCV peripheral corneal vascularization, max maximum, HOA high order aberrations. a NKL Contactlenzen (Emmen, the Netherlands). a Left eye Orbscan topography: vertical bowtie pattern on the keratometry map showing residual high with-the-rule astigmatism. b Left eye cobalt blue filter image with fluorescein dye showing an apical clearance fit pattern. (Refraction: +2.75/−12.50 × 165° [6/9]; Rose K corneo-scleral lens 6.40 mm BC/−11.00 D/14.40 mm Dia [6/7.5]). a Right eye Pentacam tomography showing an inferior steepening pattern on keratometry map with corresponding posterior elevation on the posterior elevation map. b Right eye cobalt blue filter image with fluorescein dye showing an apical bearing fit pattern. (Refraction: pl/−8.00 × 95° [6/15]; Capricornia corneo-scleral lens 6.80 mm BC/−10.50 D/13.50 mm Dia [6/7.5]). a Right eye slit lamp photograph showing a well centered scleral lens with adequate corneal clearance. b Adequate scleral lens edge lift with no blanching of the conjunctival vessels seen. (F4 lens [Innovative Sclerals, UK] 8.27BC/−0.25D/14.50 mm scleral radius/23 mm overall diameter [6/9]). Old versus new classification of scleral lenses according to the Scleral Lens Education Society (SLS). Definitions New classification (2015) [ ]—corneal/scleral bearing Old classification (2010) [ ]—diameter Corneal Lens rests on the cornea only 8.0–12.5 mm Corneo-scleral Corneal bearing and scleral touch 12.5–15.0 mm (previously known as semi-scleral) Scleral Mini-scleral: scleral bearing and minimal corneal touch (Lens is up to 6 mm larger than HVID) Mini-scleral: 15.0–18.0 mm Large-scleral: scleral bearing and maximum corneal touch (Lens is more than 6 mm larger than HVID) Large-scleral: 18.0–25.0 mm HVID horizontal visible iris diameter. The Rose K2 XL lens, a corneo-scleral contact lens, provided good visual acuity (BCLCVA 0.09 logMAR) and comfort for patients with irregular corneas [ 37 ]. In patients unsuitable for conventional GP lens wear, scleral lens wear could be a good alternative, with all patients in a study achieving a BCLCVA of 6/12 (20/40) or better [ 38 ]. In patients with corneal ectasia, prosthetic replacement of the ocular surface ecosystem (PROSE) custom lens wear has been shown to be effective with a lens wear of 88% at 6 months and an improvement in NEI VFQ-25 score of 27.6 points ( p  < 0.001) on a 100-point scale [ 39 ]. PROSE custom lenses are designed by using proprietary computer-assisted design and manufacture US patented software that is linked to a manufacturing lathe to create a smooth lens surface and to allow for control of the vault of the lens independent of base curve radius. PROSE treatment is an excellent alternative to keratoplasty for eyes with ectasia that are contact lens intolerant. Jupiter scleral lenses (15.0–24.0 mm in diameter) have also been shown to produce good results with 73% of patients reporting a BCLCVA of 20/30 (6/9) or better and 78% finding the lens comfortable in a study by Pecego et al. [ 40 ]. In a Korean population, MSD miniscleral lenses (15.8 mm) are also suitable for keratoconus patients, with a mean logMAR acuity of 0.10 ± 0.11. Overall, 97% of patients reported comfortable lens wear and the mean daily lens wear time was  10.1 ± 2.3 h [ 41 ]. Bitangential scleral lenses (20 mm) are effective for keratoconus with a median decimal BCVA of 0.8 in one study [ 42 ]. Bitangential scleral lenses have a non-rotationally symmetrical periphery that aims to enable gentle positioning on the scleral surface, increasing fitting tolerance and optimal centration. A new bitangential mini-scleral lens has also been developed by Otten et al. (Visser Contact Lens Practice, Nijmegen-Utrecht, the Netherlands) (median diameter 16 mm; range: 15.5–17 mm). These lenses provided good VA with a median BCLCVA of 0.022 (logMAR) and were comfortable (79% reported a comfort score of either a 4 or 5 (out of 5), 82% wore their lenses 12 h or longer a day) [ 43 ]. A study by Koppen et al. showed that scleral lenses reduce the need for corneal transplants in severe keratoconus, with 40 out of 51 eyes successfully treated with long-term scleral lens wear instead of undergoing corneal transplant surgery and a mean gain in VA (lens vs. spectacle-corrected VA) of 0.54 ± 0.18 (decimal) [ 44 ]. SoftPerm hybrid lenses are also effective with 83.3% achieving 20/40 or better VA [ 45 ]. However, SoftPerm lenses were fraught with complications such as corneal neovascularization, poor tear exchange, and tearing of the lens at the junction of the soft and GP portions and as such, these lenses were discontinued in 2010. Post corneal cross-linking GP lens wear post-CXL is relatively well-tolerated (Table 7 ), likely due to decreased corneal sensitivity and the flattening effect of CXL [ 46 ]. Unlu et al. found that after CXL, the mean duration of GP lens wear increased from 6.4 h/day (pre-CXL) to 12.6 h/day (3 months post-CXL) and 13.2 h/day (6 months post-CXL) [ 46 ]. However, certain problems have been identified in the use of GP lenses post-CXL. Sehra et al. evaluated the effect of GP lens wear after corneal cross-linking in keratoconus patients and noted that there is a delay in the regeneration of the corneal sub-basal nerve plexus when compared with spectacle lens wear after cross-linking [ 47 ]. Contact lens efficacy and comfort in keratoconus patients (post-surgery). Author Study design/indications Contact lens type No. of eyes Follow-up (months) Keratometry (D) BCLCVA (logMAR) Contrast sensitivity Wear-time (hours) Cons Unlu et al. [ ] Case series/post-CXL GP 30 6 56.89 ± 4.60 NA NA 13.2 ± 1.7 NA Sehra et al. [ ] Prospective comparative/post-CXL GP CXL-CL: 26 CXL-GL: 21 K-CL: 25 9 (CXL pts), 6 (non-CXL) NA NA NA NA Delay in regeneration of CSNP and epithelial cell stress Singh et al. [ ] Prospective interventional case series/post-CXL GP 20 6 Mean K: 48.6 ± 3.3 0.07 ± 0.10 (  = 0.012) 1.3 ± 0.2 (  = 0.000); 0.3 ± 0.3 (  = 0.002) 9 ± 1.89 NA Visser et al. [ ] Prospective case series/post-CXL Scleral 18 12 NA 0.03 NA 16 NA Fernando-Velazquez et al. [ ] Retrospective case review/post-ICRS Hydrogel silicone (Kerasoft-IC) 30 10.3 ± 2.3 NA 0.04 ± 0.05 (  < 0.0001) NA 11.2 ± 1.2 Corneal injection Carracedo et al. [ ] Prospective, cross-sectional, double-blind/post-ICRS Soft (Hioxifilcon A and Lucifilcon A) 14 – Steep K: 52.49 ± 3.05 Flat K: 48.54 ± 3.58 Hioxifilcon A: 0.28 ± 0.13 for 0.4 mm (  = 0.046). Lucifilcon A: 0.29 ± 0.18 for 0.4 mm (  = 0.043). – – – Montalt et al. [ ] Case series/post-ICRS Corneo-scleral (Scleracon, Lenticon, Madrid, Spain) 27 12 Central K: 46.79 ± 4.67 0.00 ± 0.12 (  < 0.001) Improved 11.78 ± 3.93 NA Carballo-Alvarez et al. [ ] Case series/post-ICRS Soft and Piggyback 47 1 KM3: 47.70 ± 4.65 0.07 ± 0.09 (soft lens) NA NA NA Rocha et al. [ ] Retrospective/post-PK Mini-scleral GP (ESCLERA™ contact lenses - Mediphacos, Buritis, MG, Brazil) 27 NA Kmax: 58.4 ± 7.8 0.09 ± 0.12 NA NA Discontinuation of lens (4 eyes), Microbial keratitis (1 eye) Barnett et al. [ ] Retrospective/post-PK Jupiter scleral 48 2 weeks–2 years NA 20/25 (scleral) NA NA NA Geerards et al. [ ] Retrospective case series/post-PK Large-diameter (12 mm) tricurve GP 190 6 Steep K: 44.75 ± 5.32 20/25 NA 9.2 Punctate keratitis D diopter, BCLCVA best contact lens corrected visual acuity, CXL cross-linking, GP gas permeable, NA not applicable, CL contact lens, GL glasses, K-CL keratoconus patients on contact lens who did not undergo CXL, CSNP corneal sub-basal nerve plexus, ICRS intrastromal corneal ring segment, K keratometry, KM3 mean corneal power in the 3.00 mm central zone, PK penetrating keratoplasty, max maximum. a Lowest spatial frequency. b Highest spatial frequency. For scleral lenses, the duration of lens wear remained stable at a mean of 16 h/day both pre-CXL and 1-year post-CXL [ 48 ]. A good VA of 0.03 logMAR was achieved [ 48 ]. In a prospective interventional case series by Singh et al, GP lenses were fitted in post-CXL patients [ 49 ]. BCLCVA post-CXL initially worsened from a pre-operative level of 0.21 ± 0.27 logMAR to 0.51 ± 0.15 logMAR ( p  = 0.000) at 2 weeks post-CXL before gradually improving to 0.01 ± 0.10 logMAR ( p  = 0.012) at 6 months post-CXL. Contrast sensitivity assessed by FACT chart also improved from 1.1 ± 3.9 to 1.3 ± 0.2 (lowest spatial frequency, p  = 0.000) and from 0 to 0.3 ± 0.3 (highest spatial frequency, p  = 0.002) at 6 months follow up. Keratometric values were also significantly reduced 6 months postoperatively and duration of contact lens use increased from 1.25 ± 1.80 h preoperatively to 9 ± 1.89 h 6 months postoperatively ( p  = 0.000) [ 49 ]. Post intrastromal corneal ring segment (ICRS) As a result of modification of the corneal shape after ICRS implantation, contact lens fitting may be more challenging, especially GP lens fitting. Hence the use of different types of lenses (soft, scleral, corneoscleral, and piggyback) has been investigated in patients who previously underwent ICRS implantation. Overall, these lenses show good efficacy in the treatment of keratoconus post-ICRS implantation with good VA and function (Table 7 ). Similar to non-ICRS keratoconic patients, SCL fitting was only successful in Stage I and II keratoconus (mild to moderate), with 75% and 66.66% of post-ICRS patients respectively successfully fitted, whereas none of the patients with stage III keratoconus were fitted successfully [ 50 ]. Piggyback lenses were a good alternative for such patients [ 50 ]. Kerasoft IC lenses are effective in post-ICRS patients with low rates of complications and adequate VA and wearing time [ 51 ]. Kerasoft IC lenses (14–15.50 mm) (Ultravision International Limited, Bedfordshire, UK) are custom-lathe soft SiHy lenses that allows for a customized selection of central and peripheral regions. SCL central thickness equal or superior to 0.4 mm affects visual function in patients post-ICRS by decreasing ocular high order aberration (HOA) and improving visual function [ 52 ]. A corneo-scleral lens (Scleracon, Lenticon, Madrid, Spain; diameter: 12.60–13.50 mm) was designed with a multi-aspherical geometry design based on three curves (base curve, intermediate or small transition curve, and peripheral or scleral curve) [ 53 ]. This lens provided good VA (BCLCVA: 0.00 ± 0.12 [logMAR]; BSCVA: 0.22 ± 0.17 [logMAR]; p  < 0.001), a 33% decrease in total HOAs  (from 2.62 ± 1.31 to 1.75 ± 1.81 μm; p  < 0.009) and an improvement in spatial frequencies of contrast sensitivity (all p  < 0.05). The lens was also comfortable with 70.37% of patients reporting high ratings of subjective visual quality and mean wear time of 11.78 ± 3.93 h [ 53 ]. Post penetrating keratoplasty (PK) In patients who previously underwent (PK), contact lens wear is sometimes necessary for residual refractive error or recurrent disease. Contact lens fitting may be challenging after PK because of the corneal profile which is usually centrally flat and peripherally steep as a result of the graft–host junction. GP lenses usually lead to decentration and intolerance. The use of hydrogel lenses is limited due to the inability of these lenses to correct irregular or highly astigmatic corneas. In recent years, miniscleral RGP, scleral, and large diameter RGP lenses have been shown to be effective (Table 7 ). Miniscleral RGP lenses (ESCLERA™ contact lenses—Mediphacos, Buritis, MG, Brazil) were particularly successful in post PK patients previously unable to wear GP contact lenses [ 54 ]. However, lens use was discontinued in four eyes and microbial keratitis developed in one eye during follow-up [ 54 ]. BCVA obtained with the Jupiter scleral lenses (15.6–18.4-mm diameter) (Essilor Contact Lens Division, Dallas, TX) have been shown to be better than prior spectacle refraction or habitual contact lenses (most commonly GP) by two BCVA lines [ 55 ]. Overall, 91.7% of eyes achieved functional vision with BCLCVAs (Jupiter scleral lens) of 20/40 or better [ 55 ]. Tricurve RGP lenses with large diameters (12 mm) have been successfully fitted in 47% of 190 PK patients with good tolerance at the Rotterdam Eye Hospital [ 56 ]. Assessing satisfaction Patient comfort and satisfaction while wearing contact lenses is an important factor that affects patient compliance. The relationship between rigid contact lens comfort and keratoconus disease severity is still equivocal (Table 8 ). In the CLEK study, Edrington et al. identified factors associated with rigid contact lens comfort in keratoconus patients and found no association between decreasing patient-reported comfort and increasing disease severity as measured by steep keratometry or first definite apical clearance lens [ 57 ]. However, Wu et al. found that patients with severe keratoconus showed significantly reduced wearing time, NEI-VFQ-25 scores and overall satisfaction compared with patients with mild-to-moderate keratoconus [ 58 ]. Patient satisfaction and comfort with different types of contact lenses. Author Study design Contact lens type No. of eyes Severity Follow-up (months) BCLCVA Comfort Wear-time (hours) Edrington et al. [ ] Longitudinal cohort GP and polymethyl methacrylate 751 Comfortable: 52.97 ± 5.40 Irritating: 53.50 ± 5.60 NA High contrast entrance VA (letters correct): Comfortable: 44.88 ± 9.16 Irritating: 42.11 ± 9.54 Low contrast entrance VA (letters correct): Comfortable: 30.98 ± 10.28 Irritating: 28.04 ± 10.26 Comfortable: 13.70 ± 3.90 Irritating: 10.62 ± 5.04 Erdurmus et al. [ ] Cross-sectional GP (40), hybrid (20), soft toric (11) 71 <45D: 1 45–52D: 33 >52D: 37 GP: 17; Hybrid: 9.9; Soft toric: 20.2 GP: 18/25 Hybrid: 18/25 Soft toric: 20/25 CLIQ person measure RGP: 45.5 ± 8.2 Hybrid: 45.4 ± 7.5 Soft toric: 48.4 ± 10.5 GP: 13.5 ± 2.2 Hybrid: 12.5 ± 2.7 Soft toric: 11.6 ± 2.4 Yildiz et al. [ ] Cross-sectional GP and Soft silicone-hydrogel 27 Steep K GP: 52.3 ± 5.3 SHCL: 50.2 ± 4.8 NA GP: 0.06 ± 0.05 SHCL: 0.1 ± 0.1 CLIQ person measure GP: 42.8 ± 5.5 SHCL: 39.6 ± 5.5 (P = 0.06) NA Bergmanson et al. [ ] Cross-sectional Scleral 24 NA NA NA Patients preferred and experienced less dryness with scleral CL 14 Wu et al. [ ] Comparative GP 46 pts Mild: 9 Moderate: 19 Severe: 18 NA Mean binocular VA score: Mild: 89.7 ± 6.2 Moderate: 82.1 ± 9.4 Severe: 73.3 ± 8.6 Mild > moderate > severe Mild: 10.4 ± 1.4 Moderate: 9.6 ± 1.7 Severe: 4.8 ± 2.5 BCLCVA best contact lens corrected visual acuity, GP gas permeable, VA visual acuity, pts patients, D diopters, CLIQ Contact Lens Impact on Quality of Life Questionnaire, K keratoconus, SHCL silicone hydrogel contact lens, NA not applicable, CL contact lens. According to the CLEK study, the apical fitting relationship (flat vs. steep) does not appear to be associated with patient-reported comfort. Minimal peripheral clearance may contribute to decreased rigid contact lens comfort in keratoconus [ 57 ]. The impact of contact lens wear on quality of life in keratoconus patients appears to be similar between RGP, hybrid, soft toric, and silicone-hydrogel keratoconus lenses as can be seen by similar scores on the Contact Lens Impact on Quality of Life (CLIQ) Questionnaire [ 59 , 60 ]. Scleral lenses (17–18.2 mm) have a higher patient-reported comfort and satisfaction as compared with habitual lenses (mainly GP but also include soft, piggyback, and hybrid lenses) though midday fogging remains a limitation for many wearers [ 61 ]. Scleral lenses with their large diameter allow for vaulting over the irregular and steep corneas and also enable for more comfortable lens wear as the edge of the lens is not felt while blinking. However, a significant limitation in the assessment of quality of life in keratoconus patients is the lack of validated quality of life questionnaires specific for the keratoconus population [ 62 ]. Complications Corneal structural changes. Contact lens use in keratoconic patients has been associated with various structural changes such as decreased basal epithelial cell density, stromal keratocyte density, and endothelial cell count. Basal epithelial cell density has already been shown to be decreased in patients with keratoconus [ 63 – 65 ]. GP contact lens wear further decreases the basal epithelial cell density as compared with non-contact- lens-wearing keratoconus patients [ 66 , 67 ]. Patel et al. postulated that this decrease in basal epithelial cell density was due to the pathophysiology of keratoconus further worsened by contact lens wear [ 68 ]. Many studies have shown a decrease in stromal keratocyte density in keratoconic corneas as compared with normal corneas [ 67 , 69 – 71 ]. The effect of contact lens use on keratocyte density in keratoconus patients is still equivocal. Some studies have shown a further significant decrease in stromal keratocyte density in keratoconus patients who wear contact lenses (both GP and soft lenses) as compared with non-contact- lens-wearing keratoconus patients [ 66 , 69 ], while others report no statistically significant difference between the two groups [ 65 , 67 ]. Most of these studies looked at the effect of GP lenses on the corneal structure [ 66 , 67 ], one study included both GP and soft lenses [ 69 ] and one study did not specify the type of contact lens used [ 65 ]. It has been hypothesized that contact lens wear causes epithelial injury which triggers the production of apoptotic cytokines which reduce keratocyte density [ 69 ]. Conversely, a study by Acar et al. demonstrated an increase in posterior keratocyte density in piggyback and ClearKone lens wearers [ 72 ]. Endothelial cell count has been shown to be decreased by up to 18% in keratoconic patients using SoftPerm lenses but not in keratoconic patients using GP or soft lenses [ 70 , 73 ]. The low oxygen permeability rates of SoftPerm lenses as compared with GP and soft lenses could explain the lower endothelial cell counts observed. Cases of significant corneal edema have also been reported in keratoconus patients wearing hybrid lenses (SoftPerm and ClearKone SynergEyes), likely due to corneal hypoxia [ 74 , 75 ]. Other manifestations of corneal hypoxia in SoftPerm lens wear include peripheral corneal neovascularization [ 45 ]. A few studies have shown a link between keratoconus and dry eye, with a higher prevalence of clinical signs such as lower tear break up times (TBUT) and corneal staining, a higher concentration of pro-inflammatory markers such as interleukins and metalloproteinases in keratoconus patients [ 76 – 78 ]. GP wear has been shown to further exacerbate dry eye signs and symptoms in keratoconus patients. In a study by Carracedo et al., among keratoconus patients, GP wearers had lower Schirmer test scores and TBUT, higher diadenosine tetraphosphate (Ap4A) concentrations and higher symptom scores (McMonnies questionnaire) as compared with spectacle wearers [ 79 ]. A study by Moon et al. also found lower TBUTs and goblet cell densities in patients wearing GP for keratoconus or myopia [ 80 ]. Acar et al. found increases in IL-6 and IL-8 levels in keratoconus patients wearing piggyback and ClearKone contact lenses [ 72 ]. Conversely, scleral lenses have been noted to improve signs and symptoms of dry eye. A different study by Carracedo et al. showed that scleral lens wears had significantly lower Ocular Surface Disease Index scores and tear osmolarity but no changes were observed in Schirmer test scores and TBUT [ 81 ]. Ocular discomfort due to dry eye could contribute to increased eye rubbing seen in patients with keratoconus, a risk factor for keratoconus progression [ 82 , 83 ]. Infectious keratitis, though rare, is one of the most sight-threatening complications of contact lens wear. The type and material of contact lens affects the risk of keratitis and there is currently no study that shows that keratoconus patients have different incidences of infective keratitis than any other patients wearing similar types of contact lenses. In an epidemiological study performed in Australia, the annualised incidence of microbial keratitis per 10,000 wearers was lowest in daily wear GP CL wearers at 1.2 (confidence interval [CI], 1.1–1.5).  In order of increasing incidence of microbial keratitis per 10,000 wearers are the following lenses: daily wear soft CL wearers at 1.9 (CI, 1.8–2.0); daily disposable CL wearers at 2.0 (CI, 1.7–2.4); soft CL wearers (occasional overnight use) at 2.2 (CI, 2.0–2.5); daily disposable CL wearers (occasional overnight use) at 4.2 (CI, 3.1–6.6); SiHy CL wearers (occasional overnight use) at 5.5 (CI, 4.5–7.2); daily wear SiHy CL wearers at 11.9 (CI, 10.0–14.6); overnight wear soft CL wearers at 19.5 (CI, 14.6–29.5) and inovernight wear of SiHy at 25.4 (CI, 21.2–31.5) [ 84 ]. Hence the incidence of contact lens-related microbial keratitis was lowest in GP lens wearers, higher in soft lens wearers and the highest in overnight soft lens wearers [ 84 ]. In keratoconus patients, acanthamoeba keratitis has been reported in scleral lens users [ 85 ]. Possible risk factors suggested for microbial keratitis in scleral lens wearers were the large diameter of the contact lens which predisposes  to corneal hypoxia, the use of large amounts of saline solution for scleral lens fitting and poor lens storage [ 85 ]. Noninfective keratitis has also been reported in a keratoconus patient wearing mini-scleral lenses [ 86 ]. Fitting techniques There has been a change in the contact fitting technique for keratoconus over the years from an apical touch to a three-point touch technique. Zadnik et al. reported on the safety and efficacy of flat- and steep-fitting rigid contact lenses in 761 keratoconus eyes in the CLEK study [ 87 ]. The results showed that, contrary to popular belief, keratoconic eyes fitted with an apical touch fluorescein pattern did not have an increased risk of being scarred centrally at baseline [ 87 ]. However at the end of the study there was a significant difference in the development of scarring and in the likelihood of requiring PK between flat fit lens patients and apical clearance fit lens patients. Another study compared the three-point-touch and apical touch fitting approaches in Rose K2 GP lenses in 109 eyes [ 88 ]. No statistically significant differences in optimal lens fit rates were found between three-point-touch and apical touch fitting approaches and between nipple and oval cones [ 88 ]. Sorbara et al. performed a retrospective review on the use of corneal topography to determine the types of keratoconus (centred or nipple, oval cones, severe cones or pellucid marginal degeneration (PMD)) and the type of GP lens that fitted optimally based on the type of keratoconus [ 89 ]. Inventory sets for keratoconus that had progressively smaller BOZDs (back optic zone diameter) as the base curve steepened were found to fit best when prescribed for centred or nipple cones and those that had a constant BOZD with a certain lens diameter that did not vary with the base curve were found to perform better on oval cones. Very large cones, as with PMD benefited from lenses with very large BOZDs [ 89 ]. Several studies looked at topographical predictors of the best base curve radius for GP lens fitting. The predictors include: K-minimum for pancorneal GP lens fitting [ 90 ], 5-mm average keratometry on the axial map for Rose K lens fitting [ 91 ], anterior chamber depth on Pentacam corneal tomography for Esclera (R) scleral contact lens fitting [ 92 ], and mean weighted corneal sagittal height at a 7.4-mm chord for ClearKone lens fitting [ 93 ]. Computerized contact lens fitting has been shown to reduce chair time in contact lens fitting and improve visual performance. A new web-based algorithm (free access at www.calculens.com ) for selecting the back-optic zone radius of spherical GP lens in keratoconus eyes was found to improve spherical KAKC GP fitting (Conoptica) [ 94 ]. Two studies compared FITSCAN (a contact lens fitting software in built in the Orbscan TM II z (Bausch & Lomb Surgical, Rochester, NY)) and conventionally fitted GP lenses and found that there was a slight bias towards flatter apical fitting in the Fitscan design [ 95 , 96 ]. One of the studies showed that selecting the BC of the initial trial lens 0.22 mm steeper than the FITSCAN calculated base curve may help to reduce the complexity of GP contact lens fitting in keratoconus [ 95 ]. Wavefront-guided scleral lens correction in keratoconus optically compensates for HOA  concomitant with the disease and can provide visual image quality equivalent to that seen in normal eyes [ 97 ]. EyePrintPRO (Advanced Vision Technologies, Lakewood, Colo.), a new customized impression-guided scleral lens fitted with 3D technology, was recently developed [ 98 ]. After creating an impression mold over the ocular surface using polyvinyl siloxane material, the mold is then scanned with a 3D scanner. Lathe technology is subsequently used to create the posterior surface of the scleral lens according to the contours of the mold [ 98 ]. A piggyback lens fitting study found that negative-powered SCLs provide a flatter anterior surface in comparison with positive-powered lenses in subjects with keratoconus and thus they might be more suitable for piggyback contact lens fitting [ 99 ]. Scheimpflug imaging and anterior segment optical coherent tomography (ASOCT) are useful in scleral contact lens fitting [ 92 , 100 ]. Pentacam (Oculus, Germany) measurements such as anterior chamber depth and pentacam-measured corneal height can be good predictors of the most appropriate Esclera lens to be fitted in keratoconus patients [ 92 ]. Likewise, corneal sagittal height measured with Visante OCT (Carl Zeiss, Germany) is an effective method of determining the appropriate lens/cornea relationship for scleral contact lenses [ 100 ]. The scleral lens vault (PROSE, Boston Foundation for Sight, Needham Heights, MA, USA) measured with ASOCT reduced significantly after 4 h of lens wear during scleral lens trial indicating that the final assessment of the scleral lens may be performed after 4 h of lens wear [ 101 ]. In another study, the corneal sagittal height measured with the Visante OCT showed a likelihood of clearance loss after 1 h of scleral lens wear [ 102 ]. Esen et al. looked at the influence of apical clearance on mini-scleral lens settling, clinical performance, and corneal thickness changes [ 103 ]. The average amount of settling was 62.8 μm after 8 h, 80% of which occurred during the first 4 h. Settling rate was significantly lower in the low apical clearance group ( P  = 0.01) with the smaller diameter lenses settling more ( P  = 0.03). Slight corneal swelling (1.3%) occurred after 8 h of wear. Another study looked at anterior corneal curvature and aberration changes after scleral lens wear in keratoconus patients with and without ring segments and found that short-term scleral lens wear showed flattening of the anterior corneal surface in all subjects [ 50 ]. Spectral domain OCT can image and measure the tear film thickness in keratoconic patients with different fitting patterns of GP lenses, in particular Rose K2 lenses and can be used to evaluate and modify the lens parameters to increase patient satisfaction. Lens intolerance may be related to edge lift rather than central fitting [ 104 ]. Despite advances in the surgical treatment of keratoconus, contact lenses remain an important and popular option for visual rehabilitation in keratoconus, with various designs enabling a large proportion of patients to attain satisfactory VA. [ 12 – 14 , 16 – 18 , 57 ] New contact lens designs and materials have significantly expanded the available fitting options for keratoconus patients. GP lens wear provided significantly better vision and improved three-dimensional depth perception as compared with glasses [ 20 , 21 ]. Among GP lens types, special cone lens design lenses such as Rose K lenses had better patient comfort levels though there was no difference in BCLCVA among the GP lenses [ 19 – 21 , 23 ]. Soft lenses show good efficacy for the treatment of mild-to-moderate keratoconus with newer designs improving visual performance such as customised hydrogel contact lenses incorporating vertical coma correction and novel pinhole soft lens reducing higher order aberrations [ 29 – 31 ]. Scleral and hybrid lenses provide good VA and comfort for keratoconic patients, some of whom were previously intolerant to GP lenses [ 37 – 43 ]. Newer design scleral lenses have expanded the scope and comfort of contact lens wear for keratoconus patients. GP lens wear post-CXL is relatively well-tolerated, likely due to decreased corneal sensitivity and the flattening effect of CXL [ 46 ]. Contact lenses may still be required post intrastromal corneal ring procedures and post keratoplasty and in these conditions, custom soft lenses and scleral lenses are more successful than GP lenses due to the altered post-surgical corneal shape. Imaging technology, such as corneal topography and anterior segment optical coherence tomography, can be utilized to guide contact lens fitting and to better understand the corneal microstructural changes associated with contact lens wear. Several topographical predictors of the best base curve radius for GP, scleral and hybrid lens fitting and computerized contact lens fitting techniques are now available which reduce the complexity and chair time of lens fitting as well as improving comfort and visual performance [ 90 – 97 ]. A new customized impression-guided scleral lens fitted with 3D technology was recently developed which further improved the accuracy of scleral lens fitting [ 98 ]. Future areas of research such as comparative studies to analyse the efficacy and comfort of the various contact lens types and validated quality of life questionnaires specific to the keratoconus population would enhance discussion on this subject. Another area of future research would be to compare the outcome of contemporary surgical options for keratoconus to that of contact lens wear. Compliance with ethical standards The authors declare that they have no conflict of interest. Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. 102 IMAGES Advanced Keratoconus: Case Study Advanced Keratoconus: Case Study Very Early Keratoconus: Case Study Central Keratoconus: Case Study Advanced Keratoconus: Case Study Advanced Keratoconus: Case Study VIDEO Keratoconus Corrections @GulaniVision KERATOCONUS management of keratoconus; part 3 Speaking with keratoconus patients about research and treatments Keratoconus Contact Lens MCG researchers study keratoconus COMMENTS A Case of Early Keratoconus Associated with Eye Rubbing in a Young Child A retrospective study in a pediatric population in Saudi Arabia similarly detected keratoconus in 2.30% of patients 6 to 16 years of age . The youngest patients with keratoconus reported so far in the literature are a 4-year-old girl from Turkey and a 4-year-old girl with Down syndrome from Switzerland [4, 7]. Although limited data presently ... New Keratoconus Risk Factors: A Cross-Sectional Case—Control Study Methods. This observational study occurred from June 2019 to February 2021 in a university hospital (France). The case group consisted of 195 patients with keratoconus in at least one eye who were followed up by a corneal specialist. The control group consisted of 195 patients without any evidence of keratoconus on slit-lamp examination and ... Management of keratoconus: an updated review Studies comparing C-CXL and I-CXL in early keratoconus have shown comparable effects in stabilizing progressive keratoconus (138, 139). Another study reported that at a 2-year follow-up, I-CXL could halt keratoconus, albeit less efficiently than C-CXL (80 vs. 92.5%). They reported a demarcation line at a depth of 216 μm observed in 35% of cases. Keratoconus: An updated review Keratoconus is a bilateral and asymmetric disease which results in progressive thinning and steeping of the cornea leading to irregular astigmatism and decreased visual acuity. Traditionally, the condition has been described as a noninflammatory disease; however, more recently it has been associated with ocular inflammation. Fourteen years follow-up of a stable unilateral Keratoconus: unique Our study focuses on a single patient therefore it illustrates the mere possibility that unilateral keratoconus exists. We present the case of a 19-year-old male with no previous ocular or general health conditions who presented to our clinic in November 2006 for incidental finding of decreased vision of the right eye (OD) on a routine examination. The Prevalence and Risk Factors for Keratoconus: A Systematic Review The outcome of the study was the prevalence of keratoconus and its risk factors, including eye rubbing, family history of keratoconus, atopy, allergy, asthma, eczema, diabetes type I and type II, and sex. Results: In this study, 3996 articles were retrieved, of which 29 were analyzed. These 29 articles included 7,158,241 participants from 15 ... A Case-Control Study of Keratoconus Risk Factors Purpose: To evaluate risk factors associated with keratoconus in a case-control setting. Methods: This single center, prospective, case-control study was carried out from May 2014 to November 2017 at the Rothschild Foundation (Paris, France). Two hundred two patients with keratoconus and 355 control patients were investigated and followed by a single ophthalmologist. A Case-Control Study of Keratoconus Risk Factors : Cornea This single center, prospective, case-control study was carried out from May 2014 to November 2017 at the Rothschild Foundation (Paris, France). Two hundred two patients with keratoconus and 355 control patients were investigated and followed by a single ophthalmologist. New dawn for keratoconus treatment: potential strategies for corneal Keratoconus is a progressive corneal ectatic disorder characterized by thinning of corneal stroma and asymmetrical conical protrusion of the cornea, which can lead to visual impairment or even blindness [1,2,3].Keratoconus is one of the leading indications for corneal transplantation surgery worldwide [4, 5], with an incidence of 1/2000 in the general population and even higher among young ... A multi-ethnic genome-wide association study implicates ... Keratoconus is a leading cause for visual impairment in adolescents and young adults which, untreated, can lead to legal blindness 1,2,3,4,5,6,7.The prevalence of keratoconus varies between ethnic ... Very Early Keratoconus: Case Study Case Study. A 40-year-old male presented for follow-up for keratoconus and for evaluation for corneal collagen cross-linking in his right eye. His best-corrected visual acuity on the Snellen chart was 20/20 in both eyes with a rigid gas permeable lens in his right eye and spectacle correction in his left eye. Current perspectives in the management of keratoconus with contact In a study on 130 keratoconus patients (228 eyes) in the United Kingdom, GP lenses of the spherical, elliptical and special cone lens design were used in 96.1% of eyes [12]. With contact lens wear ... Keratoconus: A historical and prospective review Not every case of keratoconus is progressive. Progression is related to some factors, such as young age and eye rubbing. Confirmation of progression has been an area of research and debate. The very early studies depended on a single or a few parameters to describe progressions, such as the change in K-max, refraction, or corneal thickness. A Case of Early Keratoconus Associated with Eye Rubbing in a Young Introduction Keratoconus usually presents during puberty and is considered rare in young children. Methods Case report with clinical findings and computerized corneal tomography. Results We report the case of an 8-year-old girl with early bilateral keratoconus who presented with allergic conjunctivitis and persistent eye rubbing. Although our patient did not exhibit steep keratometry, early ... Keratoconus: An updated review Epidemiological studies indicate substantial global variation as the prevalence and incidence rates of keratoconus have been estimated to be between 0.2 and 4,790 per 100,000 persons and 1.5 and 25 per 100,000 persons/year, respectively (Table 1; Fig. 1, Fig. 2), with the highest prevalence and incidence rates typically occurring in 20 to 30 year olds [27], [28], [29]. New Keratoconus Risk Factors: A Cross-Sectional Case—Control Study observational study occurred from June 2019 to February 202 1 in a university hospital (France). e case group consisted of 195 patients with keratoconus in at least one eye who were followed up by ... Advanced Keratoconus: Case Study Case study 1. A 14-year-old female patient with a history of ocular allergy controlled with eye drops and progressive advanced keratoconus (KC) in both eyes presented for evaluation, complaining of worsening of the vision in both eyes in the last 6 months. Despite having new rigid contact lenses (RCLs), she was unable to wear them long enough ... Effects of Scleral Contact Lenses for Keratoconus Management on Visual The present study was designed as a prospective case series. The study was approved by the ethical board of the Sapienza University of Rome, Umberto I Hospital, and was conducted in accordance with the tenets of the Declaration of Helsinki. ... Corneal abrasion associated with contact lens correction of keratoconus-a retrospective study. Keratoconus and Personality Traits: A Case-Control Study Purpose: The aim of this study was to delineate the personality traits of patients affected by keratoconus (KC) compared with a group of nonkeratoconic controls matched in age and sex. Methods: In this prospective interventional case-control study, 60 consecutive subjects (30 KC cases and 30 healthy controls), aged 18 to 30, were enrolled at the time of their first encounter at the ... Keratoconus: What Surprises the Experts? For keratoconus suspects, asking pertinent questions about a history of eczema, asthma, allergy, and eye rubbing should be a part of the entering case history. 1 In those already diagnosed with keratoconus, the aforementioned conditions still need to be managed, as well as sleep apnea, connective tissue disorders, inflammatory bowel disease ... Trends, Challenges and Controversies in Keratoconus In the meantime, early identification of keratoconus in adolescents and young adults who may progress rapidly remains a challenge. Fig. 2. Tangential topography of a 53-year-old male, which confirmed a first-time diagnosis of keratoconus. Best-spectacle corrected visual acuity was 20/20- in each eye with -0.50-2.00X038 OD and -0.50-2.50X137 OS. Keratoconus Clinical Presentation: History, Physical, Causes Kymes SM, Walline JJ, Zadnik K, Sterling J, Gordon MO, Collaborative Longitudinal Evaluation of Keratoconus Study Group. Changes in the quality-of-life of people with keratoconus. ... Siscovick D, Aldave A. Variation in the lysyl oxidase (LOX) gene is associated with keratoconus in family-based and case-control studies. Invest Ophthalmol Vis ... Current perspectives in the management of keratoconus with contact Introduction. Keratoconus is a progressive noninflammatory ectatic disorder of the cornea characterized by thinning and protrusion of the cornea leading to irregular astigmatism, myopia and poor vision [].It is the most common corneal ectatic condition with a prevalence of about 54 per 100,000 people in the United States [].A more recent nation-wide study performed in the Netherlands showed ... assignment essay homework paper phd report resume review speech thesis