Article

THE SCOPE STUDY: AN OVERVIEW

This study evaluated the who, what, why, and how of scleral lens prescribing.

The SCOPE (Scleral Lenses in Current Ophthalmic Practice Evaluation) study group was formed in 2014 and received initial organizational support from the Fellows Doing Research special interest group of the American Academy of Optometry. The group consists of clinicians who have extensive scleral lens experience and an interest in better understanding the role and performance of these devices in clinical practice. Members (Drs. Muriel Schornack, Jenny Fogt, Jennifer Harthan, Amy Nau, Cherie Nau, Ellen Shorter, and advisor Joe Barr) represent a variety of practice modalities, including private practice, optometric education, and academic medical practice; members bring their own unique perspective to the group. Our goal is to systematically explore clinical aspects of scleral lens practice and to engage in translational research related to scleral lenses.

At the time of the SCOPE study group’s formation, the use of scleral lenses was rapidly expanding beyond tertiary care centers and into specialty contact lens practices. This rapid growth was facilitated by a proliferation of new scleral lens designs from nearly every major specialty contact lens manufacturer. As more eyecare providers began to fit scleral lenses, many experienced scleral lens fitters have generously offered to share their personal experiences with those who were beginning to incorporate the devices into their practices. However, this expert advice was frequently based upon individual practice patterns and preferences rather than an objective study of optimal fitting characteristics. Because of this, the advice offered by one expert sometimes differed from the suggestions offered by another. As the field of experts grew, so did the potential for variability in scleral lens prescription and management practices.

A review of peer-reviewed scleral lens literature published in early 2015 demonstrated that approximately half of the articles pertaining to sclerals published between 1983 and the end of 2014 were case reports or retrospective case series that described the use of particular scleral lens designs in individual practices.1 The remainder of literature published during that time period consisted of reviews of ocular systemic conditions for which sclerals were being prescribed, prospective observational studies, retrospective observational studies, or descriptions of various lens designs. There were no studies that evaluated scleral lens outcomes across multiple lens designs or practices. Generalizable data on scleral lens prescription and management practices did not exist.

When scleral lenses were used only to manage severe corneal irregularity or ocular surface disease, and were only prescribed in tertiary care centers, the pool of patients who wore scleral lenses and the group of eyecare providers who prescribed them were too small to allow for the formation of specific guidelines for their use. Each case of ocular pathology was unique; the best scleral lens solution for one such condition could vary considerably from what would be considered ideal in another patient. However, wider dissemination of scleral lens use should make it possible to explore similarities among cases and to begin to develop some level of consensus on best practices for scleral lens prescription and management.

In consideration of all of these factors, we decided to explore the current state of scleral lens practice. We wanted to find out who was fitting scleral lenses, conditions and indications for which these lenses were being prescribed, scleral lens designs being used, recommendations for wearing schedules and care products, and what complications had been observed in scleral lens wearers. Data gathered both could provide scleral lens fitters with information on common prescription and management practices and could provide baseline data from which more targeted studies could be developed.

Our initial project was a cross-sectional study of scleral lens prescribers. In conjunction with the Mayo Clinic Survey Research Center, we designed a 25-item survey for distribution to individuals who had demonstrated an interest in contact lens fitting through membership in professional organizations dedicated to advancement of contact lens-related knowledge and skill. The study was reviewed by the Mayo Clinic Institutional Review Board and was in compliance with the tenets of the Declaration of Helsinki.

The survey was available between Jan. 15, 2015 and Mar. 31, 2015. The survey was distributed via e-mail to all members of the Scleral Lens Education Society (SLS); the Cornea, Contact Lenses and Refractive Technologies section of the American Academy of Optometry (AAO); the Contact Lens and Cornea section of the American Optometric Association (AOA), and the Contact Lens Association of Ophthalmologists (CLAO). Survey respondents were given the opportunity to suggest names of additional scleral lens fitters who were subsequently invited to participate via e-mail. In addition to direct e-mail solicitation, a link to the survey was included in the Feb. 2015 and Mar. 2015 editions of the I-Site electronic newsletter.

The survey was sent to 4,407 individuals who were members of contact lens organizations and to an additional 226 individuals who were suggested by other participants. Individuals who did not respond to their initial e-mail invitations were sent up to three additional reminders at three-week intervals.

RESULTS

A total of 989 individuals responded to the survey. A number of respondents declined to answer all of the questions asked, so the number of responses for each item was less than 989. We were primarily interested in collecting data on prescribing patterns of individuals who had established at least some level of confidence with scleral lens fitting, although we also wanted to capture basic information on individuals who had just begun to prescribe scleral lenses. Thus, individuals who reported fitting less than five patients with scleral lenses were asked to provide demographic data only (first question only). Fitters who reported fitting five or more patients with scleral lenses (n = 723) were asked to complete the entire survey; results presented for the remaining questions summarize responses from these providers.

Who is fitting scleral lenses? Among our respondents, males outnumbered females (61%, 489 out of 800 responses). This percentage is approximately representative of the optometric profession at large. The National Eye Care Workforce Study, conducted in 2014, estimated that approximately 60% of optometrists are male.2

Figure 1 shows the age range of our respondents. We also asked respondents to identify the year in which their training was completed (Figure 2). While these questions provide similar information, we wanted to account for individuals who may have entered eye care as a second career or delayed their training for any other reason.

Figure 1. Age of survey participants.

Figure 2. Year of training completion of survey respondents.

We hypothesized that older individuals who may have completed their training before corneal GP lenses and hydrogel lenses became widely available may have continued to fit scleral lenses throughout their careers. Mid-career individuals, who trained following the introduction of other lens modalities, would have likely received little exposure to scleral lenses during their training and may have therefore been less likely to incorporate scleral lenses into their practices. The recent revival of interest in scleral lenses has led to inclusion of the topic in contact lens curricula, so we suspected that younger individuals who had received instruction in scleral lens fitting may be more likely to fit this modality.

Indeed, we found that individuals aged 25 to 34 years old made up the largest group of scleral lens fitters. However, scleral lens fitters were relatively evenly distributed across other age ranges, with a predictable drop in the number of fitters over the age of 65 (due to retirement). This suggests that mid-career eyecare providers are embracing scleral lenses as a useful addition to their contact lens practices.

Distribution of respondents according to year of training completion does suggest that recent graduates may be more likely to fit scleral lenses compared to individuals who graduated prior to 2009. An average of 15.6 respondents reported completion of training in each year from 1950 to 2008. From 2009 to 2014, the average number of respondents reporting completion of training each year was 39.5. Looking at this data in another way, nearly 30% of respondents completed their training in 2009 or later. This certainly would suggest that inclusion of scleral lenses in contact lens curricula may encourage their use in clinical practice.

We asked respondents to tell us the year in which they fit their first scleral lens (Figure 3). Although scleral lenses fabricated from GP materials were first described in 1983,3 lenses made of polymethylmethacrylate (PMMA) had been used throughout the 20th century. This explains the small number of providers who began to fit scleral lenses well before the introduction of GP lens designs. It is interesting to note that the earliest hint of resurgence in interest in scleral lenses appears to have begun more than two decades after the introduction of lenses fabricated from GP materials. Our data indicates that more than 50% of our respondents fit their first scleral lens in 2010 or later. Additionally, more than 80% began fitting scleral lenses in 2007 or later.

Figure 3. Year of first scleral lens fit.

Next, we asked respondents to identify their primary mode of practice. Although most peer-reviewed studies on outcomes of scleral lens wear originated from specialty contact lens practices or tertiary care centers, the volume of scleral lens-related articles in other publications, along with the number of scleral lens-related lectures and workshops being offered independently and in conjunction with professional meetings, suggested that scleral lenses were certainly being prescribed outside of these settings. More than half of our respondents did, in fact, work in either private, group, or retail practice (Figure 4).

Figure 4. Mode of practice of scleral lens fitters.

Although a majority of the scleral lens-related studies published prior to 2014 originated from the United States, practices in 14 different countries were represented in that body of literature. In this first SCOPE survey, 72% of respondents reported practicing in the United States, 4% were from Canada, and 3% were from India (n = 799); an additional 47 countries were represented by survey participants.

For whom are scleral lenses being prescribed? To give us an idea of the number of patients who have been fit with scleral lenses, we asked providers to estimate the number of patients for whom they had prescribed scleral lenses. In total, 84,375 patients were represented by individuals who completed the survey. The mean number of patients fit by each provider was 125 (range 5 to 3,600). Most respondents (69%, n = 678) had fit 50 or fewer patients, but 13% reported fitting more than 200 patients.

Respondents also were asked to estimate the percentages of their scleral lens patients in each of the following categories: corneal irregularity, ocular surface disease, and refractive error. Responses were averaged to estimate the distribution of patients who wore lenses for each of these general indications. Results were consistent with previously published literature. Corneal irregularity was reported as the most common indication for scleral lens wear at 74%, followed by ocular surface disease (16%) and refractive error (10%) (n = 673). Participants were also asked to identify all of the specific conditions for which they had prescribed scleral lenses. Figure 5 shows the responses.

Figure 5. Conditions for which scleral lenses have been prescribed.

In addition to identifying conditions for which scleral lenses were being fit, we also wanted to explore the placement of scleral lenses within the overall management of corneal irregularity and ocular surface disease. We asked respondents to rank various forms of intervention for these general indications in the order in which they would consider each therapeutic option. Corneal GP lenses were ranked as the first option considered for optical correction of corneal irregularity by 44% of respondents (n = 629), but scleral lenses were considered first-line therapy by 34% of respondents. According to our results, scleral lenses appear to be used more frequently compared to hybrid lenses, custom hydrogels or silicone hydrogels, or piggyback lens systems for this indication. In the management of ocular surface disease, scleral lenses were reportedly used after lubricant drops, topical medications, and punctal occlusion, but before moisture chamber glasses, autologous serum tears, amniotic membrane grafts, and surgical intervention (such as tarsorrhaphy or conjunctival flaps).

How are scleral lenses being fit? Participants were asked to estimate the percentage of lenses that they had prescribed in each of three diameter categories (less than 15mm, 15mm to 17mm, greater than 17mm). Responses were then averaged to determine a mean percentage of lenses prescribed in each of these diameter ranges (Figure 6).

Figure 6. Distribution of lens diameters prescribed.

Participants were also asked to identify all of the specific lens designs that they had utilized. All lens designs available in the United States when the survey was administered were included as keyed responses; participants could also indicate lens designs utilized through free-text entries. Not surprisingly, lens designs that were used most frequently were those that had been on the market for the longest periods of time. A total of 60 different designs were reported. Given that the survey was conducted several years ago, data on usage of specific lens designs may no longer be accurate. New scleral lens designs have been introduced, and some of the earliest lens designs may have been eclipsed by these newer models. It is distinctly possible that the number of lens designs currently in use is even greater than it was in 2015.

We also asked about the use of anterior segment imaging equipment during the scleral lens fitting process. Participants were asked to identify all testing performed. Figure 7 shows the number of respondents who reported utilization of various imaging techniques. Additional testing equipment was identified within free text responses and included endothelial cell density, corneal pachymetry, confocal microscopy, aberrometry, and assessment of the ocular surface profile. Corneal topography was the most commonly performed test, and only about half of respondents to this item reported that they routinely obtained anterior segment optical coherence tomography or Scheimpflug imaging during the course of scleral lens fitting.

Figure 7. Testing performed during the course of scleral lens fitting.

How are patients instructed to wear and care for their lenses? The average wearing time recommended following lens adaptation was 11.8 hours daily (range 2 hours to 19 hours). Several authors have suggested that periodic removal of scleral lenses during the course of the day may improve comfort or vision with lens wear and may contribute to successful lens wear.4,5 Participants were asked to indicate the frequency with which they recommended midday removal of lenses to their patients. A majority of fitters indicated that they recommend periodic removal and reapplication of lenses some, most, or all of the time (Figure 8).

Figure 8. Frequency of recommendation for midday removal.

Survey respondents were asked to specify products that they recommended to fill the bowl of the lens prior to application. Nonpreserved saline products, delivered either in single-use doses (393 of 653 respondents [60%]) or as bottled products (375 of 653 respondents [57%]) were most commonly recommended. Nonpreserved artificial tears were recommended by 215 respondents (33%). Between 1% and 10% of providers recommended filling the bowl of the lens with aerosol saline solution, preserved saline, multipurpose soft lens disinfection solution, preserved artificial tears, GP lens conditioning solution, tap water, and autologous serum tears. Since the administration of the survey, one of the products listed (a bottled, nonpreserved saline) has been taken off the market, and several new products specifically designed for use with scleral lenses have been introduced. Despite these changes in availability of specific products, we suspect that most providers recommend some form of nonpreserved saline for lens application.

Providers were asked to indicate all products that they recommended for disinfection and storage. The most commonly recommended were hydrogen peroxide disinfection products (399 of 651 respondents [61%]). However, GP lens conditioning solutions were also recommended (354 of 651 respondents [54%]), as were multipurpose GP products (321 of 651 respondents [49%]), and multipurpose solutions designed for use with hydrogel lenses (71 of 651 respondents [11%]).

Participants were also asked how frequently they recommended that patients rinse their lenses with tap water. Figure 9 shows these results.

Figure 9. Frequency of recommendation for tap water rinse.

What ocular issues or complications have been observed in patients who wear scleral lenses? Very few complications associated with scleral lens wear have been reported, despite the fact that scleral lenses tend to be prescribed for individuals who have some form of ocular pathology. As of yet, published literature includes only isolated case reports of microbial keratitis.6-8 Because we asked survey respondents simply to estimate the number of patients who had been fit with scleral lenses and did not ask them to report on the number of years of lens wear for each patient, our study design did not allow for the calculation of incidence of various complications.

We did, however, ask fitters to estimate the number of their patients who had experienced a complication associated with lens wear. The most commonly reported complication was ocular surface injury due to handling or application error (444 patients). Relatively small numbers of patients were reported to have experienced various forms of corneal pathology, including corneal edema (382 patients), neovascularization (238 patients), corneal infiltrates (144 patients), and toxic keratopathy (142 patients). Survey respondents reported only 70 cases of microbial keratitis (from an estimated 84,375 patients represented). While this may seem encouraging, we would point out that these numbers are very rough estimates only and may be inaccurate due to recall or reporting bias. Nonetheless, results suggest that vision-threatening complications associated with scleral lens wear may be relatively rare.

SUMMARY

Response rate to the SCOPE survey was less than 15%. While relatively low response rates are not uncommon in survey research, we must be aware of the potential selection bias that may be present in our results. We intentionally cast a wide net and attempted to reach as many potential scleral lens fitters as possible by including all members of several contact lens-related organizations. We did not expect all members of these organizations to be active scleral lens fitters. Our study did show that there are more than 700 individuals worldwide who have at least some level of interest and proficiency in fitting scleral lenses. We can also assume that at least 84,000 patients from more than 50 countries have been fit with scleral lenses.

A wide variety of scleral lens designs are now commercially available, and scleral lenses are now available in community as well as in specialty practices. As more providers begin to offer scleral lenses in their practices, patients should be able to more easily access the lenses without having to travel to tertiary care centers. Improved access means that increasing numbers of patients will be able to experience the benefits of scleral lenses. However, it also means that more patients will be exposed to potential risks that may eventually be associated with scleral lens wear. As access to scleral lenses expands, it will become not only possible, but necessary, to begin to describe complications of scleral lens wear and risk factors for the development of those complications. With an ever-expanding pool of scleral lens fitters currently in practice, we should be able to begin to develop multicenter studies that will produce generalizable data on outcomes of scleral lens wear, evidence-based guidelines for optimal scleral lens fit characteristics, and calculation of incidence rates for various complications of lens wear.

Because of the design of the SCOPE study, conclusions that can be drawn are limited by several factors. Utilization of an internet-based delivery system may have led to an under-representation of less technically savvy individuals. The survey was presented only in English. All of the organizations whose members received direct invitations to participate were based in the United States, although membership in several of these organizations is open to individuals who reside elsewhere. It is possible that these factors led to over-representation of scleral lens practice within the United States.

We did not ask respondents to review all records of their scleral lens patients, so our data is based upon estimates of various parameters rather than absolute numbers. Recall bias and inaccurate estimation could certainly have affected our results.

The survey was administered in 2015, and practice patterns may have changed between administration of the survey and the present due to availability of new lenses or care products or the publication of new research on scleral lenses and their effects on the ocular surface.

However, the survey does offer a snapshot of how scleral lenses were being prescribed in 2015. It provided baseline data upon which further studies can be developed. Results raised additional questions regarding how and why scleral lenses are prescribed and led to the development of several additional projects, including an assessment of scleral lens fitting goals and a study of outcomes of scleral lens wear in individual patients. Given the rapidly changing landscape of the scleral lens industry, it may be interesting to design and administer a similar survey in several years to assess changes in patterns of scleral lens prescription and management.

Note: Further analyses of results are available in the SCOPE study group’s papers published in Eye and Contact Lens.9,10 CLS

The SCOPE study group would like to thank the Global Specialty Lens Symposium, AAO, AOA, CLAO, SLS, editors and staff of the I-Site newsletter, and all scleral lens fitters who took the time to complete the survey. We would also like to acknowledge support from the Mayo Clinic and Research to Prevent Blindness.

REFERENCES

  1. Schornack MM. Scleral lenses: a literature review. Eye Contact Lens. 2015 Jan;41:3-11.
  2. American Optometric Association, Association of Schools and Colleges of Optometry. National Eye Care Workforce Study: Supply and Demand Projections. 2014.
  3. Ezekiel DF. Gas permeable haptic lenses. Contact Lens Anterior Eye. 1983 Oct;6:158-161.
  4. Visser ES, Visser R, van Lier HJ, Otten HM. Modern scleral lenses part II: patient satisfaction. Eye Contact Lens. 2007 Jan;33:21-25.
  5. Ortenberg I, Behrman S, Geraisy W, Barequet IS. Wearing time as a measure of success of scleral lenses for patients with irregular astigmatism. Eye Contact Lens. 2013 Nov;39:381-384.
  6. Zimmerman AB, Marks A. Microbial keratitis secondary to unintended poor compliance with scleral gas-permeable contact lenses. Eye Contact Lens. 2014 Jan;40:e1-e4.
  7. Fernandes M, Sharma S. Polymicrobial and microsporidial keratitis in a patient using Boston scleral contact lens for Sjogren’s syndrome and ocular cicatricial pemphigoid. Contact Lens Anterior Eye. 2013 Apr;36:95-97.
  8. Bruce AS, Nguyen LM. Acute red eye (non-ulcerative keratitis) associated with mini-scleral contact lens wear for keratoconus. Clin Exp Optom. 2013 Mar;96:245-248.
  9. Harthan J, Nau CB, Barr J, et al. Scleral Lens Prescription and Management Practices: The SCOPE Study. Eye Contact Lens. 2017 Apr 6. [Epub ahead of print]
  10. Nau CB, Harthan J, Shorter E, et al. Demographic Characteristics and Prescribing Patterns of Scleral Lens Fitters: The SCOPE Study. Eye Contact Lens. 2017 Jun 14. [Epub ahead of print]