Article

SCLERAL LENSES FOR EVERYONE

Expanding indications for healthy eyes create opportunities for patient satisfaction and practice growth

For many years, practitioners have had tremendous success using scleral lenses to correct irregular astigmatism and to treat ocular surface disease, even in patients with compromised corneas. Scleral lenses were the earliest type of contact lens, manufactured first from blown glass scleral shells and then from polymethyl methacrylate (PMMA).1,2 Early designs had several shortcomings, including poor oxygen transmissibility, which led to lens-induced corneal edema, corneal hypoxia, and eventually discontinuation of lens wear. In addition, each lens was handcrafted and impossible to replicate if broken or lost. With improved materials and reproducible designs, these shortcomings have been overcome.

Scleral lenses are applied with preservative-free fluid in the bowl of the lens, which continuously bathes the ocular surface. This creates a smooth anterior optical surface, correcting for corneal irregularities and improving visual acuity. If higher-order aberrations (HOAs) are present, the post-lens tear reservoir under a scleral lens can help to minimize the effect of HOAs by eliminating corneal surface irregularities.

Indications for modern scleral lenses are expanding to include not only irregular corneas but also mild-to-severe ocular surface disease.3 Scleral lenses can be used for corneas with regular, normal, prolate shapes without disease, ectasia, or irregularities; however, coexisting conditions may be present, such as ocular surface disease, including dry eye, meibomian gland dysfunction, blepharitis, or demodex. Some practitioners are now using scleral lenses to correct refractive error for normal, healthy eyes, and each year, manufacturers introduce new lens designs for healthy eyes.

Why use scleral lenses for normal, healthy eyes? They can be used to correct most refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. I believe they can also help prevent contact lens dropout and contribute to practice growth. Interest in scleral lenses continues to rise as more practitioners embrace this technology. In a 2016 survey, almost 60% of practitioners reported their use of scleral lenses had increased.4 With this growing interest in using scleral lenses for healthy corneas, we need substantial new research on the long-term effects of scleral lens wear for both irregular corneas and healthy eyes.

In this article, I discuss emerging applications for scleral lenses in healthy eyes and offer some fitting and troubleshooting tips.

PREVIOUS CONTACT LENS FAILURES

The reason for contact lens dropout is multifactorial, according to the reports of the Tear Film and Ocular Surface Society International Workshop on Contact Lens Discomfort.5 Contact lens discomfort, which eventually leads to dropout, may be caused by lens-related or environmental factors or both. According to these reports, multiple aspects can be modified to improve comfort. Modifiable contact lens parameters are material, design, fit and wear, and lens care. Environmental factors that cannot be altered include inherent patient factors (age, gender, ocular and systemic disease), modifiable patient factors (medication compliance), the ocular environment, and the external environment (humidity and air quality).

Even with advances in contact lens technology, dropout rates range from 15% to more than 20%.6-9 Under the age of 45, comfort issues are the primary reason for contact lens dropout.5 After age 45, vision and comfort are almost equally stated as the reason for dropout.10 In the soft lens-wearing population, 93% of patients were not wearing multifocal contact lenses at the time of dropout.

Scleral lenses can resolve the two primary reasons why soft contact lens wearers drop out of lens wear: poor comfort and inadequate vision, particularly in patients with astigmatism and presbyopia.9 Because of their excellent stability and gas permeable optics, scleral lenses provide superb vision, and if needed, front toric optics can correct residual astigmatism. For patients who experience glare and halos with contact lens wear, scleral lenses offer a solution by virtue of their larger optical zone diameter (OZD). Typically, the OZD of soft contact lenses is 6 mm to 7 mm, which may be reduced to 4 mm to 5 mm in toric designs.11 Scleral lenses offer an OZD of 8 mm to 9 mm, which can be customized and made even larger if needed. Thus, scleral lenses reduce halos and glare and improve vision, even in difficult conditions, such as driving at night.

In a study that evaluated frequent or constant dryness and discomfort in patients currently wearing soft contact lenses, 23% reported dryness, 13% reported discomfort, and 27% reported at least 2 hours of uncomfortable lens wear.12 Corresponding ocular signs included limbal hyperemia (6%), bulbar hyperemia (10%), and corneal staining 12%.12

To address comfort issues, scleral lenses are applied with preservative-free fluid that constantly bathes the ocular surface. A 2012 study of patients with dry eye whose symptoms could not be controlled by conventional treatments found that mini-scleral lenses effectively decreased lens discomfort and dry eye symptoms, decreased the frequency of artificial tear use, and improved visual acuity.13 Thus, scleral lenses can benefit wearers who experience lens-induced dryness.

Diurnal variation in symptoms associated with ocular discomfort in contact lens wearers and non-contact lens wearers has also been evaluated.14 Researchers used the Ocular Surface Disease Index (OSDI) questionnaire to assess overall symptoms to evaluate diurnal changes in comfort, grittiness, stinging, irritation, and vision.

Contact lens wearers and symptomatic non-contact lens wearers exhibited a significantly greater diurnal decrease in comfort and subjective vision.14 The contact lens wearers reported significantly more dryness, grittiness, and irritation than the non-contact lens wearers.14 Interestingly, the diurnal decrease in dryness symptoms was most marked in young contact lens wearers.

In clinical practice, investigating how contact lenses feel and if patients experience fluctuating vision at the beginning, middle, and end of the day may help prevent contact lens dropout. The OSDI questionnaire is a useful tool for practitioners to use to evaluate symptoms including vision changes.14 It can be administered prior to any contact lens fitting and at subsequent visits to determine if changes are needed. If symptoms suggest contact lens discomfort or vision changes, scleral lenses can be prescribed to protect and lubricate the ocular surface.

In a recent study, researchers found that symptomatic soft contact lens wearers have poorer tear film kinetics than asymptomatic lens wearers.15 This is an area of research that needs to be explored in scleral lens wearers.

Patients who are intolerant of corneal GP lenses are ideal candidates for scleral lenses. The transition to scleral lenses is easy, and patients will benefit from crisp, clear vision and improved lens comfort — without the risk of lenses dislodging spontaneously.

SCLERAL LENSES FOR HEALTHY EYES

Several studies on the use of scleral lenses for healthy eyes have been reported in the literature. In a study of normal corneas, scleral lenses of 14.8 mm and 15.8 mm diameters were fit on 35 patients ranging in age from 19 to 37 years.16 These patients had high visual demands at distance, intermediate, and near, and they were accustomed to excellent visual acuity. Seventy-seven percent of patients successfully wore scleral lenses up to 16 hours per day and achieved logMAR visual acuity of 0.2 (Snellen 20/32) or better. The majority of patients were satisfied with scleral lenses; however, handling was the primary reason for any dissatisfaction.

Visser and colleagues assessed the performance of scleral lenses for a wide range of clinical indications.17 This cross-sectional study evaluated 281 current contact lens patients fitted with lenses based on a lens selection algorithm. The authors determined that contact lenses significantly improved corrected distance visual acuity compared to spectacles. In addition, satisfactory wearing times improved. The vision correction modality for both the scleral lens group and the soft lens group was generally effective, and each group had high subjective scores with similar results. Overall satisfaction was high in the scleral lens group (≥70 for 81% of patients).17

Researchers have also evaluated scleral lenses in asymptomatic patients with low-to-moderate (0.75D to 2.75D) refractive astigmatism. A multisite prospective crossover clinical study evaluated comfilcon A (Biofinity, CooperVision) soft toric lenses and hexafocon A (Boston XO, Bausch + Lomb) 14.3 mm diameter mini-scleral lenses in 36 patients.18 Patients wore each modality for 2 weeks and then switched modalities. One group wore soft toric lenses first, the other group wore mini-scleral lenses first. Patients preferred the vision of the mini-scleral lenses by 75% compared with the soft toric lenses in this study. There were no significant differences between the two groups in wearing time, subjective comfort, and objective vision. While 52.7% preferred to continue with mini-scleral lens wear, only 38.8% reported these mini-scleral lenses were easy or very easy to handle.18 Keep in mind that patients in this study were asymptomatic and still preferred the vision and wanted to continue with mini-scleral lenses. Thus, large-diameter GP lenses can be a good alternative to soft toric lenses to correct refractive astigmatism. These results suggest the value of offering an in-office on-eye demonstration of scleral lenses to current soft toric contact lens wearers.

Transitioning patients from other contact lens modalities to scleral lenses is not difficult and may improve their contact lens experience.

Consider patients with common refractive errors such as myopia, regular astigmatism, hyperopia, and presbyopia. If vision or comfort is not optimal with the current contact lens modality, offer the option of scleral lenses. If small amounts of spherical refractive error are present, other contact lens modalities (soft, hybrid, small-diameter GP) may be acceptable, but for patients who have significant refractive error, particularly if astigmatism is present, scleral lenses are beneficial. Even with eye movement, scleral lenses remain relatively stable on the eye.

Also consider scleral lenses for patients with astigmatism who notice fluctuating vision with soft toric lenses. Visual flux may occur with certain activities, such as changing view from a digital device to distance, or with physical movement and exercise. With their crisp GP optics and exceptional stability, scleral lenses maintain clear and consistent vision all day.

Scleral lenses are also ideal for patients with presbyopia and concomitant dry eye. There are numerous multifocal scleral lens options, including dual aspheric, center-distance, and center-near designs, that provide exceptional vision at all distances. Of note, multifocal scleral lenses can also be used in patients with irregular corneas.

SCLERAL LENSES FOR DRY EYES

Dry eye and contact lens dropout seem to go hand in hand. In clinical practice, patients with signs and symptoms of dry eye disease are more likely to experience contact lens discomfort.19 In addition, dry eye becomes increasingly frequent with advancing age, which may exacerbate contact lens discomfort.

Because scleral lenses protect and bathe the ocular surface, they are excellent for patients with presbyopia and dry eye. For patients with otherwise healthy eyes who have astigmatism, presbyopia, and dry eye, scleral lenses are good options. An in-office demonstration is extremely beneficial for these patients.

SCLERAL LENSES FOR ATHLETES

Many of the characteristics of scleral lenses make them particularly well suited to athletes, and practitioners often prescribe them for patients with healthy eyes who participate in sports, including snow and water skiing, bicycling, and gymnastics. Just the fact that scleral lenses remain stable without dislodging with quick movements make them a fantastic option for athletes.

What’s more, athletes are often exposed to challenging environmental conditions, such as wind, dust, chalk, or sand, all of which can lead to discomfort with soft contact lenses, and particularly with small-diameter GP lenses. As scleral lenses provide a sealed ocular surface environment, eyes are protected from all elements.

Athletes also have demanding visual needs. Crisp, stable, clear, consistent vision is essential for optimal athletic performance, and scleral lenses provide these benefits. The large customizable optic zone is generally advantageous but particularly for athletes with large pupils who experience nighttime flare and glare with pupil dilation.

Scleral lenses can vastly improve the quality of life for athletes, particularly those who no longer enjoy their sporting activity because of discomfort and instability with traditional contact lenses.20

While safety eyewear is recommended for all athletes, scleral lenses can help protect against trauma.21,22

TIPS FOR FITTING HEALTHY EYES

Essential tools for fitting scleral lenses on healthy eyes include keratometry, topography and/or Scheimpflug imaging, horizontal visible iris diameter, and a scleral lens diagnostic fitting set. Some manufacturers offer empirical ordering of scleral lenses for healthy eyes.

Inquire about the patient’s visual needs, including frequency of desired contact lens wear, work requirements, digital device use, hobbies, athletic activities, and general visual demands. Evaluate the anterior segment for eyelid margin disease, including blepharitis, demodex, aqueous deficiency, and elevations of the conjunctiva, such as pinguecula or pterygium. Stain and evaluate the cornea and conjunctiva with sodium fluorescein prior to scleral lens application.

Additional testing, including tear breakup time, Schirmer tear test, tear osmolarity, MMP-9, and meibomian gland evaluation, provide useful baseline data, and a dry eye questionnaire can also be helpful prior to scleral lens fitting.

Follow the manufacturer’s recommendations or the fitting guide to ensure success. After allowing the lens to settle, evaluate the fit with anterior segment optical coherence tomography (OCT) or sodium fluorescein under the lens with a slit beam using white light to determine central and peripheral lens clearance (Figure 1).

Figure 1. Scleral lens evaluation with sodium fluorescein using a slit beam with white light.

The general fitting philosophy for normal corneas is to use smaller diameter scleral lenses, also known as mini-scleral lenses. Currently, there are questions about how the combination of lens thickness, material, and post-lens fluid layer affects corneal physiology, hypoxia, and edema. Theoretical modeling studies of oxygen transmissibility and tension agree that scleral lenses should be manufactured with highly oxygen permeable (Dk) materials (>125-150+), low center thickness (200 to 250 microns), and low corneal clearances (less than 150 to 200 microns).23-27 One study demonstrated that the amount of corneal edema was 1.7% after 8 hours of scleral lens wear.28 Clinically, the reported edema is not observed and falls below physiological overnight edema, 4% without contact lens wear.29

Fortunately, for healthy eyes, smaller diameter scleral lenses (14.0 mm to 15.5 mm) are manufactured thinner (250 to 300 microns) and can use minimal clearance. In my experience, scleral lenses do not need excessive clearance to vault over the smooth, predictable surface on these corneas. Thus, smaller diameter scleral lenses can be worn successfully without inducing chronic edema on the corneal tissue; however, long-term research is still needed on the effect of scleral lenses on normal corneas.

SCLERAL LENS PROBLEM-SOLVING

Problem-solving techniques for scleral lenses for normal corneas are similar to those for larger diameter scleral lenses.

Proper care and handling of scleral lenses is critical to success, as dropout rates range from about 25% to 49%, and handling is the primary reason for dropout.30,31 Various online resources can help with scleral lens application and removal training. Be sure to caution patients that using the plunger on the center of the lens for removal will cause tremendous discomfort.

Scleral lenses must clear the cornea completely without the presence of bubbles, which can cause discomfort from focal corneal desiccation (Figure 2). Patients typically experience this discomfort 20 to 30 minutes after lens application. If bubbles are present, lenses should be removed and reapplied. Using a more viscous product in the bowl of the lens with application can help eliminate the formation of bubbles.

Figure 2. Inferior bubble in the post lens fluid reservoir.

If scleral lenses are tight and cause discomfort after 4 to 6 hours of wear, the peripheral curves need to be made flatter and/or toric. Visualizing the lens outside of the slit lamp and/or using anterior segment OCT will aid in viewing conjunctival vessel compression. If residual astigmatism is present, front toric optics can be employed.

Fogging in the post-lens fluid reservoir may occur with scleral lens wear.32,33 This post-lens tear debris may consist of various tear film components, and complications related to tear reservoir clouding are common in eyes with ocular surface disease.34 With mini-scleral lenses, there tends to be less fogging in the post-lens fluid reservoir compared with larger diameter scleral lenses.

PRACTICE MANAGEMENT PEARLS

Prescribing scleral lenses for healthy eyes can be an amazing practice-building opportunity that is financially and personally rewarding for patients and practitioners. One report noted that optometrists performed the same number of examinations per hour in 1997 as they did in 2012.35 This suggests additional opportunities exist for increasing patient volume, productivity, and profitability, specifically related to the average annual contact lens sale per contact lens examination and the average number of months elapsed between eye examinations.35,36 Particularly concerning is that the average contact lens dropout rate is 16%, even with the availability of premium designs and materials.8-10,37 This amounts to a sizable number of patients lost over the lifetime of a practice and significant lost revenue. For example, during 45 years of practice, this can have a $2 million impact.9 Not only is the individual patient lost, there is the “replacement cost” of bringing in a new patient to consider.36

If you’re interested in expanding your scleral lens practice, look to your current patients. You can offer this amazing technology to patients with astigmatism, dry eye, or presbyopia, to athletes, or simply to improve vision or comfort compared with their habitual contact lenses. Not only can this set your practice apart from others, it can result in a loyal patient base.

Once your practice is known for specialized care, patients will refer their family and friends, perhaps not for scleral lenses specifically, but for the latest in contact lens technology. Utilize manufacturers’ consultants and the Scleral Lens Education Society to stay current with the latest scleral lens technology and to help grow your specialized contact lens practice. Offer scleral lenses for healthy eyes to improve the contact lens experience and positively change the lives of both your patients and practice. CLS

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