The Use of Scleral Rigid Gas Permeable Contact Lenses in Keratoconus – A Case Report

What Is Keratoconus?

• The prevalence of keratoconus (KCN) in the United States is approximately 8.8–229 per 100,000, affecting both men and women equally.
• KCN is a progressive, noninflammatory disease resulting in ectasia of the corneal stroma.
• It causes a decrease in visual acuity (VA) from changes in corneal shape that lead to increased myopia and irregular astigmatism.

Figure 1: Corneal topography demonstrating keratoconus pattern.

Risk Factors

• The cause of KCN is still not completely understood, but studies show a correlation between the disease and several environmental and genetic factors.
• Environmental factors include eye rubbing, family history, atopy, age, ethnicity, contact lens use, and exposure to sunlight.
• Genetically, genes VSX1 and SOD1 have been highly associated with KCN pathogenesis, which is autosomal dominant but can occur in a sporadic pattern.

Corneal Collagen Cross-Linking (CXL)

• There is currently no cure for KCN, however CXL has shown promising results in slowing disease progression, especially in severe progressive cases.
• CXL uses riboflavin and a photo-oxidative reaction to increase corneal stiffness by altering the collagen within the corneal tissue.
• The changes to the collagen consist of increasing the number of covalent bonds and increasing resistance to enzymatic degradation.
• CXL has been widely used internationally for managing KCN, but was only FDA approved in the United States in April 2016.
• This treatment method has become increasingly popular since its approval.

Corneal Transplant

• Before CXL, corneal transplant was the only treatment for KCN, indicated only when the disease had progressed into more advanced stages.
• Even after a corneal transplant, patients are still at risk for developing KCN again in the transplanted cornea.
• There is a significant risk for the development of glaucoma after a corneal transplant, as demonstrated in a study by Zheng et al.
• Depending on the severity of glaucoma, treatment could be lifetime eye drops or even another ocular surgery.
• Like KCN, glaucoma is an incurable condition that can lead to blindness.
• Even though CXL and corneal transplant are both FDA-approved methods for treating KCN, they do not always help with the major side effect of the disease — reduced vision.

Why Scleral Contact Lenses?

• Due to the optics of an irregular cornea often seen in KCN, spectacles often cannot correct the vision.
• Specialty contact lenses are typically used to help maximize vision.
• Corneal rigid gas permeable contact lenses (RGPCL) are often indicated initially, but scleral rigid gas permeable contact lenses (ScCL) have shown to be an excellent, safe, and effective alternative.
• Since scleral lenses do not interact with the cornea, there is a therapeutic benefit especially for patients with severe dry eye.
• A liquid layer between the ScCL and the cornea provides constant hydration to the corneal cells.
• ScCL are often reserved for more severe KCN, but with material and fitting advancements, they should be an option at any stage of the condition.
• ScCL help patients achieve their best potential VA and can delay the possible need for a corneal transplant.
• This case report supports the benefits of using a ScCL for a patient with moderate and severe KCN, achieving 20/20 VA with optimal comfort using custom-fitted ScCL.

Case Description

Visit 1: The Consultation — Patient History

• Patient DB: 51-year-old Hispanic male, referred to Insight Vision Optometry after a comprehensive eye exam at Sam’s Club Optical in May 2021.
• The referring optometrist diagnosed the patient with myopia, astigmatism, and bilateral keratoconus with the right eye being more severe than the left.
• No spectacle prescription was recommended due to the severity of the KCN; the patient was advised that a specialty contact lens would provide better vision than glasses.
• Medical history was unremarkable — the patient denied any medical diagnoses, medications, or allergies.
• The patient was unaware of any KCN prior to the May 2021 exam and denied any other ocular conditions or surgeries.

Visit 1: Clinical Findings

• Entering unaided VA — OD: 20/200, OS: 20/25
• Anterior segment evaluation revealed corneal central inferior thinning with striae OU — mild in OS and significantly worse in OD.
• Fluorescein dye evaluation revealed mild SPK staining over the cone apex of OD.
• Nasal and temporal pingueculas noted OU.
• The rest of the anterior segment was unremarkable.
• Posterior health was evaluated via retinal imaging — unremarkable with no signs of glaucoma, macular degeneration, or any retinal disease that could contribute to the reduced vision.

Visit 1: Topography and Scleral Mapping

• A KCN pattern was observed on the topometric exam using the Medmont corneal topographer.
• An OCT and scleral mapping (sMAP) were performed over DB’s naked eye.
• The sMAP software determines sagittal depth assuming a chord length of 16mm and incorporating a 300μm buffer.

Figure 2: Scleral mapping (sMAP) and OCT imaging performed over DB’s eyes.

Visit 1: Measurements Over Naked Eye

Table 1: Measurements taken over DB’s naked eyes.

Visit 1: Europa Diagnostic Lens Parameters

• Based on the topography and scleral elevation, a Europa diagnostic lens (Visionary Optics) was selected for both eyes.

Table 2: The Europa Lens made by Visionary Optics were the diagnostic lenses used.

Visit 1: Diagnostic Lens Fit and Vision Assessment

• Lenses were allowed to settle for approximately 5 minutes before assessment.

Table 3: Fit and vision assessment of the diagnostic Europa Lens on the patient’s eyes.

Visit 1: Custom Lens Decision

• Due to DB’s high scleral toricity and high internal cylinder, a custom impression ScCL was recommended for both eyes to maximally optimize visual acuity and fit.
• Other fitting modalities were also discussed with the patient.
• Right eye (OD) — Premium custom fit: The EyePrint Prosthetic uses an impression of the eye, similar to a dental mold, to design a lens with a 3D scanner utilizing three million data points from the mold.
• Left eye (OS) — Advanced custom fit: Uses the scleral mapping scan of the eye, with special software able to design a lens from one million data points.
• Two impressions of the right eye for the custom EyePrint Prosthetic were completed in-office.
• The sMAP images were sent to the Visionary Optics Lab for the advanced custom ScCL fit for the left eye.
• All images and the over-refraction were sent to both labs for the lens design.
• The patient was expected to return to the clinic once the ScCL arrived for a training session before being dispensed.

Visit 2: Training and Dispense — Custom Lens Parameters

• An EyePrint Prosthetic ScCL was ordered for the right eye and a Latitude ScCL for the left eye.

Table 4: Custom ScCLs parameters received by the manufacturers.

Visit 2: Vision Assessment Through Custom ScCL

• The ScCLs were inserted and allowed to settle for approximately 10 minutes before assessment.
• Throughout the over-refraction, the patient reported fluctuating vision which may have been due to the lens settling, affecting the reliability of the over-refraction.

Table 5: Vision assessment through custom ScCL.

Visit 2: Lens Fit Assessment

• Clearance was determined with an anterior segment OCT, checked at the center and limbus of the cornea.

Table 6: Lens assessment of the custom ScCL on DB’s eyes after 10 minutes of settling.

Visit 2: Insertion and Removal Training

• DB was educated on how to properly insert and remove the scleral lenses using a DMV plunger to insert and a small plunger to remove.
• The patient was taught to clean and store the ScCLs using Tangible Clean Multipurpose Solution and to use sodium chloride preservative-free saline to fill the lens bowl prior to insertion.
• DB had no difficulties with removing the lenses with the small plunger.
• They were advised to place the plunger inferiorly on the lens rather than directly center, creating an uneven pressure release for the lens to come off the scleral resting points.
• There were some difficulties with insertion — DB has deeper set eyes and larger hands, making it difficult to maneuver the lens when using one hand to open the upper lid and the other to hold the lower lid and DMV plunger with the ScCL.
• The most comfortable technique for DB was using one hand to hold the upper and lower lid while the other hand solely guided the DMV and ScCL.
• A scleral stand was suggested, which acts as a third arm, allowing the patient to hold open the eyelids with both hands while moving toward the stand that props up the DMV and ScCL.
• DB expressed feeling comfortable with insertion without the scleral stand.
• DB successfully completed training by removing and inserting the ScCL, and left the clinic wearing the lenses.
• DB was scheduled to return in one week for a follow-up to recheck VA and fit, and was advised to wear the lenses as much as possible to allow for adaptation.

Visit 3: One-Week Follow-Up — Patient Report

• DB had worn the ScCL OU for 4 hours prior to the appointment.
• Average wear time was about 1 to 2 hours, due to eye fatigue during wear.
• There were difficulties with reading and intermediate distance because the vision felt “too overwhelming,” causing eye tiredness.
• DB reported seeing better at intermediate distances without ScCL.
• With lenses, OD vision was much clearer than OS vision.
• There was mild discomfort with OS at the appointment but no redness from the ScCL.
• Some difficulties with insertion persisted because DB could not get the eyes wide enough, but ScCL removal was easy with the small plunger.

Visit 3: Vision Assessment

Table 7: Vision assessment through custom ScCL at 1 week follow-up.

Visit 3: Lens Fit Assessment After 4 Hours of Wear

Table 8: Lens assessment of custom ScCL after 4 hours of wear.

Visit 3: Monovision Trial and Modifications

• Since the patient had difficulties with near and intermediate vision, a monovision fit was discussed to maximize acuity at all distances and improve visual comfort.
• It was discussed that with a monovision fit, distance vision may be reduced to compensate for near vision, and depth perception will be reduced.
• A monovision fit was trial framed, but DB could not adapt to the vision.
• The patient opted to best correct distance vision in the ScCL for part-time wear and was educated that over-the-counter reading spectacles would be necessary to optimize near vision.
• The overall fit of the lenses was acceptable; the only modification needed was to change the prescription of the left eye since entering VA was 20/50.
• A new Latitude lens was ordered to adjust the OS prescription, incorporating the over-refraction determined at this visit.
• The patient will continue with the right lens to allow more time to adapt.
• Another modification to be considered at the next dispense appointment is possibly making the OD ScCL a smaller diameter for easier insertion.
• The patient is to return to the clinic for a new OS Latitude ScCL dispense when it arrives.

Discussion

Advances in Keratoconus Diagnosis

• Before the development of the corneal topographer, the only way to diagnose KCN was through slit lamp observed clinical signs, so it was often not diagnosed until later stages.
• Corneal signs such as corneal protrusion, corneal apex thinning, Vogt’s striae, Fleischer’s ring, and corneal scarring typically represent more advanced stages.
• In earlier stages of KCN, symptoms can include reduced vision from increased myopia and irregular astigmatism, visual distortions, and light sensitivity.
• Because of constant changes in vision, patients with KCN may need to frequently change their spectacle correction.
• Now that corneal topography is more readily available, early stages of KCN can be more easily diagnosed and treatment such as CXL can be implemented sooner to slow disease progression and preserve vision.

Effectiveness of CXL

• A 10-year study by Raiskup et al. showed that CXL was effective in decreasing the progression of the disease and stabilizing the cornea long-term, ultimately reducing the need for corneal transplant.
• By stabilizing the cornea, vision is preserved — CXL provides treatment in early diagnoses, especially in adolescents, with fewer complications compared to a corneal transplant.
• The Nordström et al. study demonstrated that after one year post-CXL, subjects had decreased corneal irregularities and improved vision.
• There was also no damage or cell loss to the corneal endothelium, demonstrating that CXL is not only effective but also safe.

Scleral Lenses vs. Corneal RGP Lenses

• In early stages of the disease, spectacle correction can provide adequate vision; however, as the disease progresses, glasses are unable to mask the irregular astigmatism.
• Corneal RGPCL are common for correcting keratoconus, but ScCL are becoming increasingly popular because they provide better patient comfort.
• In a study by Levit, Benwell, and Evans, although there was no significant difference in vision or vision quality of life, KCN patients preferred ScCL over corneal RGPCL because of the significant difference in comfort.
• ScCL are preferred because of their design — they rest only on the sclera, allowing the lens to vault over the cornea entirely, minimizing any corneal interaction.

Reducing the Need for Corneal Transplant

• ScCL can help reduce the need for a corneal transplant in patients with severe keratoconus, as observed in a study by Koppen et al.
• A majority of subjects with severe KCN had a decreased need for corneal transplant when successfully fitted with ScCL.
• Subjects who still underwent a corneal transplant after ScCL fitting were those unable to tolerate the lens.
• By fitting KCN patients with ScCL rather than treating with a corneal transplant, complications associated with the surgical procedure — such as glaucoma — are reduced.

Safety of Scleral Lenses

• A retrospective study by Fuller and Wang assessed the prevalence of ScCL complications including microbial keratitis, phlyctenulosis, corneal abrasion, contact lens-induced acute red eye, corneal infiltrates, pingueculitis, and hydrops.
• Complications were observed to be related to poor wetting, poor handling, reservoir fogging, lens intolerance, deposits in the eye, and broken lenses in the eye.
• Although adverse effects occurred in a small percentage of subjects, proper ScCL fitting and patient education are important to reduce the risk of complications.
• Management options for complications include adding a surface treatment to the lens, replacing the lens, and adjusting wear time.
• Overall, the study concluded that ScCL for KCN patients are safe and effective.

Importance of Scleral Shape Assessment

• Most traditional ScCL designs assume the sclera is a uniform, spherical shape — however, this is not the case for many individuals.
• Using a sMap3D corneo-scleral topographer, DeNaeyer et al. measured the elevation of both the cornea and the sclera on 140 eyes.
• Results: approximately only 5.7% of eyes had a spherical scleral shape, 28.6% had regular toricity, and 40.7% had asymmetric elevations and depressions.
• A majority of the population have a non-spherical sclera, yet most practitioners continue to fit scleral lenses empirically with a traditional lens design.
• Common complications from poor scleral landing include conjunctival blanching, conjunctival prolapse, and surface tissue staining.
• Determining the patient’s scleral shape at the initial visit can decrease fitting chair time and improve patient comfort.

Case Outcome

• In DB’s case, the stage of KCN was well advanced, especially in the right eye, so the reduced vision of 20/200 could not be corrected with glasses.
• Scleral lenses were selected over corneal RGP for maximum comfort and optimal visual acuity.
• A custom-fit ScCL was chosen over a traditional fit because of the patient’s high scleral toricity, determined at the consultation.
• A well-fitted ScCL was achieved after just one visit.
• By using custom ScCL designs — the Latitude and EyePrint Prosthetic — the patient achieved 20/20 vision in the previously 20/200 eye while maximizing comfort and reducing the risk of ScCL complications.
• Fitting DB in a ScCL has the potential to reduce the need for a corneal transplant later in life.

Conclusion

• Fitting a ScCL can be intimidating and has a stigma of being difficult and time-consuming, requiring many follow-ups and lens adjustments.
• However, with advancements in corneal imaging and mapping, diagnosing KCN and fitting ScCL is much simpler with less chair time.
• By gaining the confidence to fit ScCL, care and services can be provided to KCN patients without the need for an additional referral.
• ScCL have been shown to be safe and effective for achieving optimal vision for KCN patients, even after a couple of months post-CXL treatment.
• By diagnosing KCN in earlier stages, CXL can be implemented to immediately stabilize the cornea before the disease progresses.
• With the added ScCL fit, the potential need for a corneal transplant is significantly reduced along with the associated complications of the surgical procedure.

References

• Leucci, M., & Carter, M. (2018). Clinical signs in keratoconus. Optometry Today (London), 58(11), 86.
• Hashemi, H., Heydarian, S., Hooshmand, E., Saatchi, M., Yekta, A., Aghamirsalim, M., Valadkhan, M., Mortazavi, M., Hashemi, A. & Khabazkhoob, M. (2020). The Prevalence and Risk Factors for Keratoconus: A Systematic Review and Meta-Analysis. Cornea, 39(2), 263–270.
• Vinciguerra, R., Romano, M. R., Camesasca, F. I., Azzolini, C., Trazza, S., Morenghi, E., & Vinciguerra, P. (2013). Corneal cross-linking as a treatment for keratoconus: Four-year morphologic and clinical outcomes with respect to patient age. Ophthalmology, 120(5), 908–916.
• Zheng, C., Yu, F., Tseng, V. L., Lum, F., & Coleman, A. L. (2018). Risk of glaucoma surgery after corneal transplant surgery in medicare patients. American Journal of Ophthalmology, 192, 104–112.
• Fuller, D. G. & Wang, Y. (2020). Safety and Efficacy of Scleral Lenses for Keratoconus. Optometry and Vision Science, 97(9), 741–748.
• Koppen, C., Kreps, E. O., Anthonissen, L., Van Hoey, M., Dhubhghaill, S. N., & Vermeulen, L. (2018). Scleral lenses reduce the need for corneal transplants in severe keratoconus. American Journal of Ophthalmology, 185, 43–47.
• Raiskup, F., Theuring, A., Pillunat, L. E., & Spoerl, E. (2015). Corneal collagen crosslinking with riboflavin and ultraviolet-A light in progressive keratoconus: Ten-year results. Journal of Cataract and Refractive Surgery, 41(1), 41–46.
• Nordström, M., Schiller, M., Fredriksson, A., & Behndig, A. (2017). Refractive improvements and safety with topography-guided corneal crosslinking for keratoconus: 1-year results. British Journal of Ophthalmology, 101(7), 920–925.
• Levit, A., Benwell, M., & Evans, B. J. W. (2020). Randomised controlled trial of corneal vs. scleral rigid gas permeable contact lenses for keratoconus and other ectatic corneal disorders. Contact Lens & Anterior Eye, 43(6), 543–552.
• DeNaeyer, G., Sanders, D., van der Worp, E., Jedlicka, J., Michaud, L., & Morrison, S. (2017). Qualitative Assessment of Scleral Shape Patterns Using a New Wide Field Ocular Surface Elevation Topographer: The SSSG Study. Journal of Contact Lens Research and Science, 1(1), 12–22.