Scleral Lens Prescription and Management Practices: Emerging Consensus

Abstract

Purpose:

To describe international scleral lens prescription and management practices across multiple practice types.

Methods:

For this cross-sectional study, scleral lens practitioners were asked to complete an electronic survey that requested information about a single scleral lens patient. Data collected included practitioner demographics (practice type, country, years of experience) and patient indications for scleral lens wear, fitting process, lens design, and care products.

Results:

Data were collected for 259 patients (419 eyes). Most participants (60%) practiced in the US, 75% worked primarily in community practice, and 58% claimed more than 5 years’ experience fitting scleral lenses. Indications for scleral lens wear were corneal irregularity (87%), ocular surface disease (9%), and uncomplicated refractive error (4%). During the fitting process, the mean (SD) number of lenses ordered was 2.4 (1.6) (range, 1–16 lenses) during 3.8 (2.4) visits (range, 1–18 visits). Of patients, 62% used a daily surfactant cleaner, 47% used hydrogen peroxide disinfection, and 67% used single-use vials of nonpreserved saline. Mean lens diameter was 16.2 (1.1) mm (range, 11.8–23.0 mm). The landing zones were spherical (64%), toric (26%), quadrant-specific (7%), and custom (3%) designs. Optical power was spherical in 70%, toric in 27%, and higher-order aberration correcting in 3% of lenses. Only 5 lenses had multifocal optics.

Conclusions:

General consensus regarding prescribing patterns (lens design, wearing schedules, care products) between US vs non-US, community vs academic, and new vs established providers is reported in this study. Relatively low percentages of patients wearing lenses with advanced landing zones or optical designs suggest that these new options have not been widely adopted.

Introduction

Prescription and management practices for scleral lenses have been studied through both single-center retrospective reviews [1–6] and survey research [7, 8]. Although useful, both approaches have limitations for understanding how scleral lenses are being prescribed. Specifically, single-center studies tend to reflect the fitting philosophy and prescription patterns preferred by a single practitioner or a relatively small group of practitioners. Findings from such research may be difficult to extrapolate to a broader population. Survey research can potentially produce more generalizable data by drawing upon practice patterns from a larger, more diverse pool of practitioners; however, survey research lacks the statistical power of prospective studies. Furthermore, prior surveys were designed to ask practitioners to estimate values for various parameters of scleral lens fitting rather than to gather specific information based on a comprehensive review of records of all patients prescribed scleral lens within their practices [7, 8].

As scleral lens practice has matured, it now seems feasible to develop evidence-based practice patterns that are based on the fitting experience of practitioners working in a variety of practice types throughout the world. A previous study suggested an emerging consensus in areas of interest such as the fitting process, lens design, recommendations for lens care products, and wearing schedules [8]. Therefore, in the survey described herein, data were collected retrospectively on scleral lens prescription and management practices across a broad and diverse sample of practitioners through review of data for a single patient from each practice. Potential recall and selection bias were minimized by random patient selection and the use of patient records to gather data.

Methods

The study was approved by the University of Illinois Institutional Review Board. The cross-sectional, multicenter study used a web-based survey designed and distributed by using REDCap (Research Electronic Data Capture) data capture tools hosted at the University of Illinois at Chicago (Chicago, Illinois) [9, 10]. The survey was available from December 13, 2016, through March 31, 2017. Links to the survey were emailed directly to 2,790 members of the Scleral Lens Education Society, 604 participants in a previous SCOPE (Scleral Lenses in Current Ophthalmic Practice Evaluation) survey who agreed to be contacted for future studies [7], and 37 additional scleral lens practitioners suggested by survey participants. In addition, links to the survey were included in 2 electronic newsletters (I-site and the British Contact Lens Association newsletter) during the survey period. Up to 2 reminders were sent to individuals who did not respond to the initial invitation to participate. No remuneration was offered to participants. Data about patients’ visual outcomes and fogging complications and the survey have been published previously [11, 12]. The present study describes the fitting process, lens design, and wear and care recommendations for this representative sample of patients.

Participants were asked to provide information about their primary type of practice, number of years of experience in fitting scleral lenses, and country of residence. Primary practice types were classified as community (private, group, and retail practices) or academic (academic institutions, hospitals, and tertiary care centers). For this study, practitioners with 5 or fewer years of experience in scleral lens fitting were classified as new, and those with 5 or more years of experience in fitting scleral lenses were classified as established. Data from practitioners who practiced in the US were compared with data from all other practitioners (referred to as international practitioners).

Participants were asked to provide detailed information about a single established patient with at least 6 months of scleral lens wear in their current lens design. Specifically, they were asked to provide information from the health record for the eligible patient they had evaluated most recently. The specific instructions about patient selection and record review were provided to minimize selection and recall bias.

Statistical Analysis

Descriptive data are reported. Comparisons made between 2 groups (US vs non-US prescribers, new vs established fitters, and academic vs community practice) were evaluated by 2-sample t tests with equal variances. Comparison of responses by indication for scleral lens wear (irregular cornea, ocular surface disease, or refractive error correction only) were evaluated using analysis of variance (ANOVA), and χ² tests were used to assess for distribution differences when comparing categorical responses by location, practice type, and fitting experience. A P value <.05 was considered as significant.

Results

Of the surveys sent, 352 individuals responded. Participants were not required to complete every survey item, and 93 of these participants did not respond to any of the items analyzed in this study. This yielded a sample of 259 patients (419 eyes) for analysis. Practitioner demographic information and patient indications for lens wear have been previously reported in detail [12]; however, the Box briefly summarizes the relevant data.

Box.

Demographic Information for Survey Participants and Indications for Scleral Lens Wear

Survey participants
Country of origin (n=225)
US: 135 (60%)
Non-US*: 90 (40%)
Main practice type (n=232)
Community (private/group/retail) practice: 173 (75%)
Academic (academic/hospital/tertiary care center) practice: 59 (25%)
Scleral lens fitting experience (n=233)
Established (>5 years): 135 (58%)
New (≤5 years): 98 (42%)
Patient indications
Indication for scleral lens wear (n=255)
Corneal irregularity: 221 (87%)
Ocular surface disease: 24 (9%)
Uncomplicated refractive error: 10 (4%)

^*Other countries represented in this sample (listed in order of the number of respondents from each country) were Italy, United Kingdom, Canada, India, Switzerland, South Africa, Spain, Australia, Columbia, Costa Rica, Greece, Mexico, Sweden, Brazil, Cyprus, Denmark, Ecuador, Germany, Namibia, Netherlands, New Zealand, Philippines, Portugal, Rwanda, and Israel.

Fitting Process (Number of Lenses and Visits)

The number of lenses ordered during the fitting process was reported for 236 patients (419 eyes). A mean (SD) of 2.4 (1.6) lenses per eye were needed to complete the fitting (range, 1–16 lenses). Practitioners based in the US ordered significantly more lenses per eye during the fitting process than those practicing outside of the US (2.6 [1.9] vs 2.0 [0.9]; P=.01 [t test]). There were no differences in number of lenses ordered based on indications for lens wear (F_2,230=0.27; P=.76 [ANOVA]). Two-sample t tests showed no statistical differences when community was compared with academic practices (P=.36) or established with new practitioners (P=.09).

The number of visits required to complete a scleral lens fit was reported for 207 patients; the mean (SD) number of visits per patient was 3.8 (2.4) (range, 1–18 visits). The number of visits did not vary by indication (F_2,201=0.12; P=.89 [ANOVA]). No significant differences were shown between the number of visits reported by US versus non-US practitioners (P=.61 [t test]) or between the number of visits reported by participants in community versus academic practices (P=.57). However, new practitioners required more visits than established fitters (4.2 [3.0] vs 3.5 [1.7]; P=.04) to complete the fitting process.

Lens Wearing Schedule and Care Regimen

Mean (SD) duration of lens wear in this patient sample was 2.5 (2.0) years (range, 0.5–16.0 years [n=257]). Patients of new practitioners had fewer years of scleral lens wear than patients of established practitioners (1.7 [1.2] vs 3.1 [2.3]; P<.001); however, no differences in duration of lens wear were shown for patients of US versus non-US practitioners (P=.40) or for those seen in community versus academic practices (P=.30 [t test]). There was no difference in mean duration of lens wear based on indication for fitting (F_2,252=0.96; P=.40 [ANOVA]).

The overall mean (SD) daily wearing time was 12.8 (2.9) hours (range, 4–18 hours). Patients who received care from US practitioners reported longer daily wearing time than those of non-US practitioners (13.3 [2.6] vs 12.2 [2.1] hours/day; P=.006), but daily wearing time did not differ based on either practice type (P=.60) or practitioner experience (P=.22 [t test]). Similarly, ANOVA revealed no differences in mean daily wearing time when indications for lens wear were compared (F_2,240=0.62; P=.50).

The lens cleaning regimen was reported for 246 patients. Of those, 152 patients (62%) used a separate daily surfactant, and use of a daily cleaner did not vary by indication for scleral lens wear (P=.10), practice type (P=.90), or practitioner experience (P=.60). However, US practitioners were less likely than international prescribers to recommend a separate daily cleaner (57%, US; 70%, international; P=.05). Disinfection and soaking solutions were reported for 245 patients. Of these patients, 116 patients (47%) used hydrogen peroxide disinfection and soaking solutions, 66 (27%) used a conditioning solution for gas permeable lenses, 45 (18%) used multipurpose solutions for gas permeable lenses, and 18 patients (7%) used soft lens multipurpose solutions. Disinfection and soaking solution use did not differ among primary indication (P=.60), practice type (P=.98), or experience (P=.50), although US patients reported higher use of hydrogen peroxide for disinfection and soaking than non-US patients (62% vs 28%; P<.001 [Pearson χ²]).

The bowl of the lens was filled before application by 243 patients using the following solutions: nonpreserved saline in single-use vials (163 [67%]), nonpreserved saline from multiuse bottles (51 [21%]), nonpreserved artificial tears (11 [5%]), preserved saline (11 [5%]), and multipurpose solution (7 [3%]). Nonpreserved saline in single-use vials was used by 75% of patients from the US compared with just 55% of non-US patients. Single-use vials were used by 80% of patients with ocular surface disease compared with 66% of those with corneal irregularity and 56% with refractive error only.

Lens Design

Lens diameter, landing zone design, and optical characteristics were recorded for each lens. The mean (SD) lens diameter reported was 16.2 (1.1) mm (range, 11.8–23.0; n=419) (Figure 1). Lens diameter differed by primary indication for lens wear (F_2,219=4.3; P=.01 [ANOVA]); however, the small number of lenses fit for ocular surface disease and correction of refractive error limited reliability of this analysis. Mean lens diameter for eyes with various indications were as follows: corneal irregularity, 16.2 (0.1) mm (n=193); ocular surface disease, 15.9 (0.4) mm (n=20); and correction of refractive error, 17.0 (0.3) mm (n=9). No differences in lens diameter were noted based on practice location (P=.87), practice type (P=.29), or practitioner experience (P=.07).

Figure 1.

Distribution of Lens Diameters. Of lenses, 8% were <15.0 mm in diameter, 68% were between 15.0 and 16.9 mm in diameter, and 24% were ≥17.0 mm in diameter.

Landing zone design was reported for 406 eyes. Spherical landing zones were most frequently prescribed (254 [63%]), followed by back-surface toric (111 [27%]), quadrant-specific (30 [7%]), and custom (11 [3%]) designs. There were no differences in scleral lens landing zone design based on indication for lens wear (P=.19), practitioner location (P=.56), practice type (P=.48), or practitioner experience (P=.67) (Pearson χ² tests). Because it was possible that patients who had been fit more recently were more likely to wear lenses with nonspherical landing zones, the distribution of landing zone designs worn by patients with less than 5 years and 5 or more years of lens wear was evaluated. Data were available for 200 participants who responded to both items (patient duration of lens wear and lens landing zone design). Figure 2 shows the distribution of landing zone design based on duration of wear for these 200 patients.

Figure 2.

Landing Zone Design Associated With Duration of Lens Wear. Spherical landing zones were common in the earliest commercially available scleral lens designs, whereas toric, quadrant-specific, and custom landing zone designs were introduced more recently. Nonetheless, there was little difference between the percentage of spherical landing zones prescribed for patients with ≥5 and <5 years of lens wear.

Optical power was reported for 407 lenses. Spherical optical power was prescribed most frequently (70%, 285 lenses), followed by front-surface toric optical power (27%, 111), and incorporation of correction for higher order aberrations (3%, 11). There were no differences in the type of optical power prescribed based on indication for scleral lens wear (P=.36), practice location (P=.41), practice type (P=.42), or practitioner experience (P=.10) (Pearson χ² tests). Of the 285 lenses with spherical power, 70 (25%) had nonspherical landing zones, compared with 76 of 111 lenses (68%) with toric optical power. Most lenses were single-vision correction; 5 lenses with multifocal optics were reported.

Discussion

The findings from this survey showed that respondents in community practice outnumbered those in academic practice, which were similar to results of a previous survey [13]. Much of published research about scleral lenses originates from a relatively limited number of academic practices [14]. Whereas survey research such as this most certainly has limitations, it does represent an opportunity for community practitioners, who may provide care for a substantial proportion of the scleral lens–wearing population, to contribute their experience to discussions regarding scleral lens prescription and management practices.

Fitting Process (Number of Lenses and Visits)

Not surprisingly, new fitters ordered more lenses per eye during the fitting process than did their more established counterparts. It was, however, interesting to note that providers based in the US ordered more lenses per eye than did their international counterparts. The reason for this disparity is unclear. No differences were noted in percentages of patients who wore advanced landing zone designs between US and international providers, so it cannot be assumed that providers outside the US have better access to superior lens designs. However, US-based and international manufacturers may have different policies on warranty exchange or remakes. Thorough exploration of these potential differences is beyond the scope of this study.

Previous studies described the efficiency of the scleral lens fitting process and reported that scleral lens fitting requires from 1.4 to 3.2 lenses per eye and 2.8 to 6.2 visits per patient [12–14]. The mean of 2 lenses per eye and 4 visits per patient reported in this study roughly aligns with these values. A prospective study by Macedo-de-Araujo et al [15] suggested that increased scleral lens fitting experience may improve the efficiency of the fitting process; they reported that mean (SD) reorders per eye decreased from 0.95 (0.74) for the first 20 patients fit by a single provider to 0.25 (0.43) for the 141st to 156th patients fit by that provider. In addition, significant improvements in fitting efficiency were reported once the provider had completed 60 scleral lens fits. Because practitioners in the current survey were asked only the number of years of scleral lens fitting experience (not the total number of lenses ever fit), practitioners who had the most experience were not able to be reliably identified. However, new practitioners did report more visits during the fitting process than established practitioners. The efficiency of the fitting process has implications for the adoption of imaging and impression-based technology for scleral lens design. Even with this advanced technology, it has been reported that a mean of 2.1 lenses (range, 1–5) per eye may be necessary to complete the fitting process[16]. Although technology-assisted fitting may eliminate the need to order a third or fourth scleral lens during the fitting process, substantial overall increases in fitting efficiency may be difficult to realize, particularly for more established practitioners.

Lens Wearing Schedule and Care Regimen

Patients included in the study had been wearing lenses for a relatively short period of time. More than half of all patients in the study had worn lenses for 2 years or less, and less than 10% had worn lenses for more than 5 years. This finding was surprising because scleral lens fitting has become mainstream in the US in the past 5 to 10 years. There are several potential explanations for this result, including the possibility of sampling bias. Another explanation is that the use of scleral lenses has more recently become common outside of the US, and 40% of the respondents practiced internationally. The short duration of lens wear might also reflect patient attitudes regarding the difficulty of wearing scleral lenses. Patients with uncomplicated refractive error or mild ocular disease may find that, while scleral lenses improve vision or comfort, the increased cost and burden of care required for their maintenance eventually overwhelms any visual or comfort advantage. Specific survival data on scleral lens wear for patients with undifferentiated dry eye disease was reported by Schornack et al [17] in 2014; of 24 patients with dry eye symptoms with substantial ocular surface-tissue compromise, only 7 still wore their scleral lenses at their most recent visit. Of patients with documented discontinuation of lens wear, the mean duration of wear was just 10 months. Further study of scleral lens survival could provide valuable information for scleral lens practitioners as they consider this treatment modality with their patients.

Overall, distribution of care products reported in this study was consistent with that reported in a previous survey of scleral lens practitioners. In the previous study, 61% of participants recommended hydrogen peroxide care products, and 60% recommended nonpreserved saline delivered in single-use vials as the filling solution [7]. However, recommendations for lens care differed between US and international practitioners. US practitioners were less likely to recommend a separate daily cleaner for their patients and were more likely to prescribe a hydrogen peroxide–based disinfection system than their international counterparts. Nonpreserved saline delivered in single-use vials was the choice of more patients in the US than of patients outside the US, who were more likely to use multipurpose solution or preserved saline as filling solutions.

Lens Design

Mean lens diameter in this cohort of patients was 16.0 mm, and 68% of lenses prescribed were between 15 and 17 mm in diameter, which is consistent with a 2015 study that estimated 65% of lenses prescribed were between 15 and 17 mm in diameter [7]. Unlike the 2015 study, which indicated roughly equal percentages of lenses <15.0 mm and >17.0 mm in diameter, only 8% of lenses in the present study were <15.0 mm in diameter, whereas 24% were ≥17.0 mm. The smallest lenses reported in this sample were 11.8 mm in diameter (1 patient, 2 eyes). These data were included because the survey did not query corneal diameter; it is possible that the lenses did, in fact, achieve scleral fitting goals (complete vault over cornea and limbus). All other lenses were ≥13.5 mm in diameter.

In this study, 63% of the lenses described had spherical landing zones, which was of considerable interest. A recent study showed that the sclera is not rotationally symmetrical in most eyes [18]. Back-surface toric landing zone designs have been commercially available for nearly a decade, and positive patient outcomes with back-surface toric landing zones were described as early as 2006.[1, 19] A previous single-center study of scleral lens prescribing practices reported that toric landing zones were prescribed for approximately 80% of patients.[15] Thus, one might have expected to see greater representation of lenses with back-surface toric or quadrant-specific landing zones in the current patient population, particularly because most patients in this sample were fit after 2015. The possibility that a greater proportion of advanced landing zone designs would be observed with shorter durations of lens wear was explored; distribution of landing zone designs in lenses fit more than 5 years ago was similar to that of lenses fit within the past 5 years. It is possible that prescription of a high proportion of lenses with back-toric landing zones in single-center studies represented a practice-specific preference for those lens designs, which may not be generalizable to the overall population of scleral lens fitters. The paucity of patients wearing lenses with impression-based or image-based designs was not surprising, however, because these lens designs have been introduced more recently and may still have somewhat limited availability. Cost may also be a factor limiting widespread use of these custom designs.

A majority of lenses worn by patients in this sample had spherical optics, although 26% of lenses incorporated front-surface toricity to optimize refractive correction. This finding supports the clinical observation that scleral lenses are usually quite rotationally stable on the ocular surface, even if back-surface toricity is not incorporated into the lens design. The use of a scleral lens platform for correction of higher-order aberrations has been proposed [20, 21], but lack of commercial availability currently limits widespread use of lenses with this advanced optical design. Indeed, only 11 patients (22 eyes) in this sample were wearing lenses that incorporated correction of higher-order aberrations. Further developments in incorporating advanced optics on a scleral lens platform could potentially improve quality of vision for some patients as such designs become more widely available.

Acceptable visual and physiologic results were obtained for this patient population [12] despite the low use of more sophisticated lens designs and optical correction, which suggests that relatively uncomplicated scleral lenses may suffice for many patients. The scleral lens landing zone rests upon relatively soft conjunctival tissue, which is not as densely innervated as corneal tissue. Both of these physiologic characteristics may allow an acceptable and comfortable fit to be achieved despite a lack of perfect alignment between the conjunctiva and the lens landing zone. Most of the patients with data in this sample had some form of ocular pathology that may have limited their visual potential, which could preclude noticeable improvement in visual acuity even with advanced optical designs. Practitioners who achieve adequate results with standard scleral lens designs may be hesitant to invest the time and money to incorporate the latest imaging technology into their practices. However, advanced scleral lens designs have been reported to be successful for patients when standard designs have failed [16, 22].

Limitations of this study include those common to all survey research. Data could only be collected from individuals who responded to the survey, which could have created sampling bias. Attempts were made to distribute the survey to as many scleral lens fitters as possible, but it is likely that not every eye care provider who fits scleral lenses was specifically invited to participate, which may have introduced prescreening or advertising bias. Not all individuals who were invited chose to participate; thus, participants who elected to participate may not have been entirely representative of all scleral lens fitters. Furthermore, the survey was available only in English, which may have led to under-representation from non-English speakers. (Although this study received responses from a higher percentage of non-US practitioners than an earlier survey of international scleral lens prescribing patterns [13], Morgan et al’s [23] report on international overall contact lens prescribing trends during the year of the current study included a much smaller sample of patients from the US [319 of 19,598].) Because this was a retrospective record review, data collected were limited by what was available in the patient’s health record, so participants were not always able to provide a response to every survey item. Survey developers attempted to balance the need for complete data for each patient with the goal of broad participation even by participants whose data may have been incomplete. The present study solicited information on only 1 patient from each participant, regardless of the participant’s total scleral lens practice volume; therefore, prescription and management practices of relatively high-volume scleral lens practitioners may be underrepresented in the current sample. Although participants were specifically directed to provide information on an established scleral lens wearer, they may have selected a patient who was unusually successful or unsuccessful with scleral lens wear. Relatively small proportions of patients with ocular surface disease and uncomplicated refractive error precluded robust analysis of any differences in prescribing patterns between various indications for lens wear. However, there was considerable agreement in distribution of indications for lens wear, lens diameter, and care regimens recommended between this study and a previous study in which participants were asked to estimate values for various practice patterns [7, 13].

This survey, to our knowledge, represents the largest multicenter description of scleral lens fitting practices published to date. Whereas the field of scleral lenses remains dynamic, the results show that certain practice patterns (such as number of lenses, visits needed to achieve a fit, and indications for scleral lens use) are solidifying as the field matures. The relatively low percentage of patients wearing lenses with toric, quadrant-specific, or customized landing zones, along with low utilization of advanced optical designs, suggests that more advanced designs have not yet been widely adopted.

Highlights.

• This study confirmed corneal irregularity as the most common indication for scleral lens wear.

• The fitting process for scleral lenses is comparable to that of other specialty lenses.

• The mean diameter of scleral lenses is approximately 16 mm.

• A majority of patients in this sample wore lenses with spherical landing zones.

• Care regimen commonly featured daily cleaner, hydrogen peroxide disinfection, and single-use vials of nonpreserved saline.

Abbreviations

ANOVA

analysis of variance

SCOPE

Scleral Lenses in Current Ophthalmic Practice Evaluation