Interest in scleral lens use continues to increase as more eyecare professionals (ECPs) understand how invaluable they are to both their practice and their patients. In fact, they are often life-changing for patients who have corneal disease or dry eye and who have been unsuccessful with other forms of contact lenses. The purpose of this article is to provide a clinical primer for ECPs desiring to incorporate scleral lenses into their practice.

GETTING STARTED

A number of excellent sources are available to help anyone interested in fitting scleral lenses. This article certainly intends to be one such source, but there are many resources, such as more than 25 archived webinars available from the GP Lens Institute (GPLI) including a recent webinar specifically on this topic from Lynette Johns, OD. The Scleral Lens Education Society (SLS) also has webinars, workshops, and care and patient education videos among their numerous resources. The “Scleral Lens Troubleshooting FAQs” resource—available on both the GPLI and SLS websites—is a well-illustrated comprehensive downloadable guide to patient selection, fitting, troubleshooting, and lens care. Likewise, “A Guide to Scleral Lens Fitting (2nd edition) from Eef van der Worp, BOptom, PhD, is a must read. For a comprehensive resource, the “bible” of scleral lenses, Contemporary Scleral Lenses: Theory and Application by Melissa Barnett, OD, and Dr. Johns, is extremely helpful. Finally, Scleral Lens Issues and Complications: Their Recognition, Etiology, and Management, a new book from Daddi Fadel, DOptom, also includes valuable information. A list of these resources and others is provided in Table 1.

The next step would be contacting a laboratory with which you already have an account and have worked with their consultants and with which you are comfortable. Express your interest in working with sclerals. The consultants should be able to provide resources (webinars, videos, fitting guides, etc.) on their specific lens design(s). Watch the webinars/videos, read the guides, and become familiar with the fitting process and then obtain your fitting set(s). If possible, ask a laboratory consultant to visit your practice to teach you hands-on for your first few fits; or, visit a practice that fits sclerals to observe for a day. Your first few fits could consist of highly motivated patients who are very likely to be successful and/or staff members. Certainly, the benefits of initially fitting a staff member include both experience and familiarity with lens handling. If it is not possible for a consultant to visit the practice, you can take photos and/or video of your initial fit(s) and send those for review. If anterior segment photography is not possible, you can search the internet for slit lamp smart phone adaptors; there are several available, and they work well.

WHO ARE THE BEST CANDIDATES?

To determine whether patients are candidates for scleral lenses, consider their medical history, ocular history, and past contact lens successes/failures and then evaluate them for possible barriers to achieving success. The typical indications for fitting sclerals can be divided into broad categories, including vision improvement, ocular surface protection, and cosmesis/sports.¹ In fact, regardless of experience, practitioners overwhelmingly fit scleral lenses on patients who had irregular corneas (74.2%), while 16% were used for dry eye and 10% for uncomplicated refractive errors (i.e., astigmatism and presbyopia).² For individuals just getting started fitting scleral lenses, choosing good candidates can help you develop skills while having success.

The best candidates for these initial fits are keratoconus patients or post-refractive surgery patients who are corneal GP lens-intolerant. They will want to see better and to have the comfort of sclerals. They also will be motivated and easier to please (less picky) compared to patients who have healthy eyes and are less complicated compared to post-graft patients. Choose keratoconus patients who are struggling with comfort, dry eyes, or fit stability. Choose post-refractive surgery patients who notice diurnal fluctuations or who have decreased acuity with glasses. Dry eye patients are certainly great candidates and are not complicated to fit, but they have more long-term issues with wetting that can make management more complex. That said, the therapeutic benefit of the tear reservoir, which scleral lenses provide as a byproduct of how they are fit, often makes this option the only contact lens alternative for dry eye sufferers. Additionally, due to this reservoir, scleral lenses can protect the ocular surface for patients who have exposure keratopathy, graft-versus-host disease (GVHD), Sjögren’s, Stevens-Johnson syndrome, trichiasis, and symptomatic dry eyes.

However, almost all irregular cornea patients can benefit from the potentially life-changing impact of scleral lenses. These lenses provide optical correction and mask astigmatism in patients who have ectasia, post-surgical corneas, post-trauma, scarring, or corneal degenerations/dystrophies. In addition, they often provide improved comfort compared to corneal GPs because they move little with the blink, do not decenter significantly, and do not rest on the highly sensitive corneal surface. With a larger diameter and optic zone compared to corneal GPs, scleral lenses can provide better centration and therefore better vision for some patients, especially in keratoconic eyes that have a decentered cone.³

For patients who have healthy eyes, fitting sets are available; they typically come with smaller diameters, are designed to vault the regular corneal surface, and provide correction for presbyopia, astigmatism, hyperopia, and myopia, even in high amounts. As scleral lenses exhibit little movement, scleral lens patients who have high astigmatism may find their vision more stable than they do with soft or corneal GP toric options. Scleral lenses are a great option to consider for patients who have hobbies or occupations that involve areas with dust/debris or water or for those who have an active lifestyle during which having their corneal GP lenses pop out could cause a significant decrease in vision and function.

LENS MATERIAL CONSIDERATIONS

As a result of the greater center thickness, very limited movement, and the presence of a large liquid tear film between lens and cornea, a hyper-oxygen-permeable (i.e., ≥ 100 Dk) material is necessary. Patients who have corneal disease or pathological dry eye—who are at greater risk for hypoxia—would benefit from the highest available Dk lens materials. Currently available hyper-Dk materials have between 160 and 200+ Dk. Additionally, ordering a lens with a polyethylene glycol (PEG) surface coating can help with surface wettability, especially with deposit-prone patients.

PRE-FITTING CONSIDERATIONS

Because scleral lenses can be more expensive, more time consuming to fit, and, in many cases, less durable compared to corneal GPs, it is helpful to talk to patients about fees, expectations, frequency of lens replacement, warranties, insurance coverage, etc. prior to entering too far into the process. This will ensure that patients are prepared for the cost and the time commitment to obtain an optimal fit.

It is also helpful to discuss the application and removal process in advance. Using a scleral lens can involve more work than a corneal GP lens can; for a long-time corneal GP wearer, the extra steps can be a negative, as can be the additional ongoing cost of the solutions and filling agents.

Prior to beginning the fitting process, carefully examine the eye and look for any factors that would impact success with scleral lenses such as endothelial disease, conjunctival obstacles, corneal vascularization, basement membrane dystrophies, etc. Obtain any diagnostic data that you can to help in the process, such as corneal topography or tomography, scleral shape imaging, or optical coherence tomography (OCT). It is important to understand that a scleral lens, despite vaulting the cornea, still provides the best outcome when it maintains a somewhat similar shape to the eye. Knowing a cornea’s topography allows you to choose a lens profile that minimizes the risk of lens-cornea touch or excessive vaulting. Scleral shape mapping technologies have greatly enhanced lens haptic customization capabilities by allowing fitters to know whether a scleral zone should be spherical, toric, or quadrant-specific from the outset of the fitting process. This translates to better patient comfort and a more efficient lens fitting process. In light of the recent pandemic, empirical scleral lens fitting may become the standard of care in the future. This will place a greater dependence on corneoscleral shape mapping technologies.

FITTING AND EVALUATION

Lens Selection When fitting diagnostically, choose your initial lens by following the fitting guide or using the instrumentation-based data that you have obtained. Keep in mind that larger corneas typically do better with larger and deeper lenses, while smaller corneas might be better off with smaller lens diameters.

Remember that choosing a scleral lens is more about sagittal depth than about curve, so choose a lens based on depth. Larger corneas, advanced cones, and post-penetrating keratoplasty (PK) corneas will all require deeper lenses. Smaller corneas, post-refractive surgery corneas, and flatter corneas will all require shallower lenses. Also remember that scleral lenses, like corneal GPs, come in standard and reverse geometry designs; the latter is often recommended for oblate post-refractive surgery corneas or for corneas that have a very decentered apex (pellucid marginal degeneration, Salzmann’s nodular degeneration, etc.). Choosing the correct lens geometry for the type of eye that you are fitting makes obtaining a good fit much easier when you are doing your final adjustments. In addition, be sure to evaluate the sclera for the presence of pingueculae, elevated cysts, scars, or symblepharon to determine the best lens diameter.⁴

Assessing the Fit Once an initial lens is selected based on diameter, geometry, and depth, prepare the lens and apply it using fluorescein in the bowl of the lens with saline to aid in visualization of the tear reservoir. Immediately assess the lens with cobalt blue light, low magnification, diffuse illumination, and a Wratten filter, if available. Ensure that there are no air bubbles and that the lens demonstrates full corneal and limbal clearance. If these initial criteria are met, then quickly assess central clearance with white light, an optic section, and moderate magnification.

If the initial vault is approximately that for which you were hoping at initial application (200 to 400 microns), allow the lens to settle for, at minimum, 20 to 30 minutes, if possible, before more carefully assessing the vault and the fit of the scleral zone. As the periphery of the lens sinks into the spongy conjunctiva, the lens will decrease in sagittal depth or “settle.” The amount of settling will vary by lens design but is often between 100 to 200 microns, with most of the settling occurring within the first eight hours of wear.⁵ The optimum clearance is 50 to 200 microns post-settling.⁶ The lens must not bear on the corneal surface; if it does, the epithelium can be disrupted by the mechanical force of such a heavy lens.

Using the slit lamp to make a thin optic cross-section, you can estimate the amount of clearance in microns between the cornea and back surface of the scleral lens. This technique is acceptable in almost all cases. Placing fluorescein in the bowl of the lens can make this measurement easier to do, and knowing the center thickness of the scleral lens in microns can make your estimation more accurate. For example, if the lens thickness (dark zone of optic section) is 250 microns, and the green zone (i.e., tear film) is approximately equal to the lens thickness, you can estimate that you have approximately 250 microns of clearance (Figure 1). The Michigan College of Optometry Scleral Lens Fit Scales (Table 1) are a valuable resource for estimating clearance.

Changing to a wide slit lamp beam is helpful to evaluate for any other areas of corneal touch, including the assessment of clearance over the limbus⁷ (Figure 2). The ideal amount of limbal clearance is 50 to 100 microns.⁶

The edge should not overly compress the conjunctiva in any region, nor should it lift off the sclera too much, as this can cause lens awareness and movement due to lid interaction. Aiming the light source in various angles while evaluating the edge can help to catch edge problems most readily (Figures 3 and 4). It may be helpful when evaluating an edge to pull the eyelids out of the way while maintaining primary gaze as much as possible; looking in any direction impacts the lens fit and alters the edge fit. Also, if the lens is decentering noticeably, manipulate the lens into a centered position, using a patient’s lids to help, and reassess the edges. Knowing that this is the position in which you would prefer the lens to stay, adjust edges to optimize the fit in this location. The most precise measurement of corneal clearance and scleral haptic landing can be taken by using an anterior segment OCT (AS-OCT). This can be especially useful in more complex, irregular cornea cases.

Disinfection Once a diagnostic scleral lens has been used, it is important to then properly disinfect it. According to the most recent International Organization of Standardization (ISO) Standards, the lens should be cleaned and then placed into a non-neutralizing lens case with an approved 3% hydrogen peroxide solution.⁸ The lens should be disinfected for, at minimum, three hours. The lens should then be rinsed with a multipurpose solution (MPS), patted dry, and then stored dry. The American Academy of Optometry (AAO), the American Optometric Association (AOA), the GPLI, and the Contact Lens Manufacturers Association (CLMA) developed a useful in-office guide with this information.⁹

After dispensing a new pair of lenses, it is recommended that patients wear their scleral lenses for a minimum of three-to-four hours before and to the initial follow-up visit. This allows for an assessment of possible complications that may not have been observed during the fitting appointment including corneal touch, inadequate limbal clearance, or haptics that become too tight or that lift up.

COMMON PROBLEMS AND THEIR MANAGEMENT

If scleral lenses were perfect, practitioners would fit them on every contact lens patient. However, we realize that managing problems with scleral lenses can be challenging at times. As mentioned before, this is where your laboratory consultant is invaluable, and any information that you can provide (e.g., topography maps, photos/video of the fit, etc.) can be the difference between success and failure. In addition, the resources in Table 1 can be beneficial, as are Facebook groups that are specific to scleral lens fitters.

Flexure Flexure with a scleral lens should be relatively easy to manage. If a lens is flexing, as evidenced by over-Ks or over-topography, it simply means that there is toricity in the sclera and the lens does not align to that toricity. Evaluate the edges carefully, center the lens by manipulation if needed, and note where the edges are too steep or flat. This should match the axis of flexure. When observed, reorder the lens with toricity in the haptic to align the scleral zone as evenly as possible, and flexure should be minimized or eliminated; again, don’t hesitate to communicate with your laboratory consultant. Rarely, if ever, should a lens need to be made thicker to deal with flexure at this point in the evolution of scleral lenses. Instead, address flexure with a proper scleral zone fit.

Post-Lens Tear Debris Tear reservoir debris is a much-debated problem among scleral lens fitters. First, manage ocular surface debris and eyelid problems to the best of your ability before attempting a scleral lens fit. Tear reservoir debris can occur for a variety of reasons, including debris from the tear layer channeling through areas of poor lens alignment or inflammatory debris from physiologic stress on the cornea.

Debris that comes from the tear layer will follow a path of fluid flow from the edge of the lens inward, and it will often start to accumulate just minutes after applying a lens (Figures 5 and 6). It also has a mildly yellow hue due to the predominant lipid presence from the tear layer. Detect this by instilling fluorescein dye and observing for leakage. If the fluorescein leakage coincides with the trail of debris (Figure 7), address the lens fit and attempt to reduce the tear flow—often through the use of toric haptics for better scleral alignment—while reducing overall vault as well to make the fogging less visually impacting.

If the reservoir debris is related to inflammation, it will be milkier and will have a whiter hue (Figure 8). It typically will not follow the flow of external tears and will take longer to accumulate. If this is the case, address the situation by evaluating the lens fit for tightness and possibly by changing the filling solution to one that contains electrolytes. Other methods to help reduce post-lens tear debris include using topical mast cell stabilizers in atopic patients, adding a more viscous nonpreserved solution into the lens bowl, or removing and reapplying the lens more frequently, as needed.^10,11

Lens Surface Deposits Deposits on a scleral lens can occur for reasons other than the simple age of the lens or wear and tear. Due to the lack of tear exchange with a scleral lens, back-surface buildup can occur in the optic zone that appears as a white film. This type of film can often be removed by aggressive manual cleaning with lens polish and a velveteen cloth or cotton swab; using a modification unit for polishing is risky, as the hyper-Dk materials are easy to damage. Front-surface deposits are quite common in patients who wear scleral lenses for ocular surface disease (OSD). The drying of the lens surface allows deposits to stick to the dry lens more readily than if the lens were wetted with tears (Figure 9). In these instances, advise patients on proper care and that they should be using a good cleaning agent immediately upon lens removal. However, it is equally important—if not more so—to manage the OSD as effectively as possible. The lens should be (re)ordered with a PEG coating, and the surface should be lubricated frequently with eye drops. Too often, surface deposits for OSD patients are deemed to be due to improper cleaning, when in fact it is drying of the lens surface that is the core problem; this must be addressed to significantly improve the depositing issue. For these individuals, temporary improvement may be experienced by rubbing the lens—while still on the eye—with a plunger or cotton-tipped applicator moistened with preservative-free saline.

Hypoxia Hypoxia is a concern for all scleral lens wearers to a certain extent, but for those who have compromised endothelial function, it is a priority to avoid. Notably, caution should be used when fitting a post-transplant patient or anyone else who has experienced endothelial cell loss. These patients should be monitored carefully using serial pachymetry, photos, and a comprehensive slit lamp examination.

The risk of hypoxia can be reduced by maintaining a thin lens profile (which requires proper scleral zone alignment to avoid flexure), keeping vault to a minimum while still maintaining full vault (100 to 150 microns but no less than 50 microns at follow up), using a smaller-diameter lens to reduce lens suction, and selecting a hyper-Dk lens material.¹² Using a lens material at this level or higher reduces the risk of hypoxia. While many corneas that have been fitted far from optimally for oxygen delivery do very well, others struggle even with all aspects of the fit optimized for oxygen. We can deduce from this that there must be another mechanism at play that contributes to hypoxia or lack thereof.

It is possible that a lens that has less tendency to “suction” to the eye will demonstrate less signs of hypoxia over time. Therefore, when all other steps have been taken to reduce the risk of hypoxia but signs still develop, adjust the lens to fit more loosely, and ensure a degree of tear exchange to make sure that oxygen gets to the cornea around the lens, not just through it. While this may encourage debris accumulation, it is a trade-off that is sometimes needed in at-risk individuals.

Impingement When the outer edge of the scleral lens pinches into the conjunctiva, the pressure is observed as blanching (whitening) of the blood vessels at the lens edge; this is called impingement.¹³ Impingement leads to decreased patient comfort with longer wearing time. It is observed clinically as redness just beyond the lens edge and as conjunctival staining after lens removal if significant. Over time, this will also lead to conjunctival hypertrophy (Figure 10). This is differentiated from compression, in which the area of tightness is usually spread over a larger area and extends under the scleral landing zone of the lens.

Impingement may be localized either toward the lens edge (toe effect) or more toward the point of initial contact with the ocular surface (heel effect). Impingement is sometimes noticeable at initial fitting, but often it takes days or weeks of wearing time to fully manifest a marginally tight edge. Matching the geometry of the landing zone to the asymmetries of the ocular surface will prevent these clinical occurrences.

Managing an edge that is impinging can be as simple as flattening the edge of the lens to alleviate the localized pressure in that meridian or quadrant. However, when impingement is very focal, sometimes a localized edge adjustment—such as a microvault or edge vault—can be implemented to lift the edge just in the specific region of the impingement. Choosing the best approach will depend on the rest of the fit and whether a change to the edge might be desirable in areas above and beyond the area of impingement.

Staining Staining may result from hypoxia, mechanical interactions between some portion of the lens and the surface epithelium, or from toxic factors. It is important to assess staining using a slit lamp with lenses both on and off after several hours of wear. Signs such as indentation rings, limbal hyperemia, and corneal staining may indicate mechanical damage occurring after lens settling (i.e., insufficient clearance and possible bearing). Microcystic edema from limbal compromise is often easier to find after fluorescein staining where cysts have ruptured and epithelial damage has occurred. Mechanical and limbal hypoxia-induced damage is often confined to smaller areas, zones, or even patches (Figures 11 and 12). In contrast, solution-induced corneal staining from toxicity resulting from instilling a preserved saline into the bowl of the lens during application tends to be diffuse (Figure 13). Common sources include use of preserved saline, MPSs, preserved artificial tears, and cases in which peroxide solutions are not neutralized properly.

Conjunctival Prolapse Conjunctival prolapse is a typically benign occurrence described as the entrapment of conjunctival tissue under the scleral lens that drapes around the inferior limbal area⁶ (Figure 14). It is more likely to occur in patients who have loose conjunctival tissue, but it may also be a result of applying the lens with too much pressure, creating a suction force.¹⁴ Although patients are asymptomatic and the potential long-term risks are not yet known, if the prolapse is significant (causing neovascularization under the prolapse or corneal staining after removal), fitting a lens with the best possible alignment to the shape of the eye, minimizing areas of excessive vault when possible through more custom-fitted designs, and reducing lens suction as much as possible will minimize this problem.

LENS CARE AND PATIENT EDUCATION

In almost all cases, scleral lenses are prescribed on a daily wear schedule, which requires daily application, removal, and disinfection. For lens application, it is essential to fill the lens bowl only with preservative-free saline to prevent toxicity to the corneal surface. There are several branded preservative-free saline products currently available on the market, or practitioners can use a sodium chloride inhalation solution. All but one are available in unit-dose form. It is important to educate your scleral lens patients throughout the fitting process on the use of acceptable preservative-free saline products, as they can be more challenging to find commercially compared to other contact lens care products. Keeping the recommended products available in your office for sample or purchase may improve patient compliance or prevent the inadvertent transition to a preserved saline solution.

For lens application, apply the saline-filled lens with the patients’ head positioned parallel to the floor or table and with their chin tucked down to avoid air bubbles in the fluid reservoir. Air bubbles usually occur from inadequately filling the lens bowl or from spilling out too much saline during application.¹⁵ It is helpful to overfill the bowl, creating a positive meniscus. Air bubbles can lead to patient discomfort as the cornea desiccates in those areas; therefore, the best practice is to initially evaluate the lens fit and to remove the lens and reapply it if a bubble is present, even if small.

Stabilizing the lens using a large plunger device is most often recommended; using an open plunger without suction (meaning the end is cut off) makes it easier to keep the lens clean and is less complicated to use because you don’t need to squeeze the plunger to release it. Some patients who have shaky hands or smaller lid apertures find the assistance of a stand to hold the plunger in place very useful. Remind patients that when they feel something touching their eye, it is the saline in the lens and not the lens itself, so they still have a quarter inch left to push before it is applied. Using a smooth motion, avoid applying the lens with too much force. It is expected that excess fluid will spill out of the bowl upon application. Wait to release the upper and lower eyelids until this occurs and the peripheral edges are contacting the conjunctival surface all around.

For lens removal, using a smaller removal suction cup device (without a hole) is the most common technique, especially with larger-diameter lenses. Always confirm that the scleral lens is actually in place on the eye before attempting removal with this device. Wet the tip of the plunger, have patients look into a mirror straight in front of them (not down), look up very slightly, and touch the plunger gently to the lower one-third of the lens (i.e., between lens edge and iris). Do not push any harder than necessary, because it only causes the lens to stick to the eye more firmly. Then, gently move the plunger away in an upward/outward motion once it is suctioned to the lens surface. Never position the plunger in the center of the lens. This can cause pressure/pain, a corneal abrasion, a dehisced corneal graft after transplantation, and ultimately unsuccessful removal of the lens from the eye. Without the plunger accessory, it is still possible to remove scleral lenses manually. Gently push the lower eyelid with your index finger under the lower edge of the lens to break suction, allowing the lens to pop out.¹

Application and removal devices should be disinfected after use and replaced every three months—the same frequency that a contact lens case is replaced. Avoid contamination of the preservative-free saline container, and strictly follow the replacement guidelines of the product to reduce the risk of infection.

After scleral lens removal, a preservative-free hydrogen peroxide disinfection system or multipurpose GP lens solution should be prescribed to disinfect and store the lenses overnight. Scleral lenses should never be stored in saline solution overnight due to the risk of microbial keratitis.¹ The scleral lens manufacturer often provides guidelines for acceptable lens care products.

SUMMARY

We hope that this guide will serve as a beneficial resource as you begin or continue your scleral lens journey—a journey that culminates in many, many, happy endings. There is little to compare in contact lens practice than watching patients cry (happy tears) after having their life changed by application of scleral lenses. CLS

REFERENCES

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11. Review of Optometry Staff. Leukocytes May Cause Scleral Lens Fogging. Rev Optom. 2019 Jan 31. Available at https://www.reviewofoptometry.com/article/leukocytes-may-cause-scleral-lens-fogging . Accessed Sept. 11, 2020.
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14. Miller W. Managing Scleral Lens-Induced Conjunctival Prolapse. Contact Lens Spectrum. 2015 Sept;30:48.
15. Mickles C, Barnett M. Simple Tips for Troubleshooting Sclerals. Rev Cornea Contact Lens. 2016 Apr 15. Available at https://www.reviewofcontactlenses.com/article/simple-tips-for-troubleshooting-sclerals . Accessed Sept. 11, 2020.