Contact lens prescribing trends for keratoconus at an academic medical center: increased utilization of scleral lenses for severe disease.

Abstract

Objectives:

To describe contact lens prescription trends for patients with keratoconus.

Methods:

Demographics, corneal curvature, visual acuity and type of contact lens prescribed were reviewed for all patients with keratoconus evaluated in the contact lens service in 2010 and 2020.

Results:

There were 292 patients in 2010 and 217 in 2020. In 2010, 69% were using corneal gas permeable lenses (GP), 16% soft toric, 13% hybrid, 2% soft sphere with no scleral lens (SL) wearers. In 2020, 60% were using corneal GP, 22% SL, 12% soft toric, 5% hybrid and 1% soft sphere. Mean LogMAR visual acuities with manifest refraction were 0.42 [0.33, 0-1.3) in 2010 and 0.35 [0.33, 0- 1.6] in 2020 improving to 0.19 [0.18, 0- 1.3; P=<.01] and 0.13 [0.14, 0- 0.60; p<.01] with contact lenses. Mean keratometry measurement in patients using SLs was 53.0 diopters [9.9, 42.1-84.5] which was steeper than 46.6 diopters in patient’s using all other lens types in 2010 and 2020 [3.9, 40.9-57.9; P<.01).

Conclusions:

SL prescription increased during the past decade; however, corneal GP lenses remain the most frequent lens prescribed for patients with keratoconus in this cohort. Despite being prescribed for patients with the most advanced disease, SLs provide good visual acuity.

Keratoconus is a non-inflammatory, primary corneal ectasia characterized by asymmetric and progressive corneal steepening, apical thinning and central scarring.¹ Based on registry data in the United States from 1935 to 1982, the occurrence of keratoconus is estimated to be 1 in 2000 with a prevalence of 54.4 cases per 100,000,² though the true incidence and prevalence is believed to be higher than previously reported, with a Netherlands study reporting a prevalence of 1 in 375.³ Visual acuity is typically reduced as keratoconus progresses. While patients with mild disease may be able to achieve acceptable vision with spectacles or soft contact lenses, many patients rely on the optics of rigid gas permeable lenses which mask irregular corneal astigmatism in order to achieve functional vision.

Although corneal gas permeable (GP) lenses have been the treatment of choice for visual correction in patients with keratoconus for more than 50 years,^4–6 scleral lenses (SL) have become an increasingly popular choice in the last decade. SLs, a large diameter of gas permeable lens which offer the same visual benefits as corneal GP lenses, were often reserved for individuals with severe keratoconus; however, this trend may be changing. In a 2020 survey of eye care practitioners who had fit at least five SLs in the past year, 41% ranked SLs as the initial correction of choice followed by 26% who ranked corneal GP’s as their first choice.^7–9 SLs have been shown to improve visual acuity and contrast sensitivity in eyes with corneal irregularity.^10–12 Previous studies have shown their prescription can decrease the need for corneal transplant in patients with advanced keratoconus; however, SLs may be considered for patients with less severe disease as well.^{4, 13} The purpose of this study is to describe changes in contact lens prescribing trends for the management of patients with keratoconus in 2010 compared to 2020 at an academic medical center.

Methods:

Medical records of all patients evaluated in the Contact Lens Service in 2010 and 2020 at the University of Illinois at Chicago Illinois Eye and Ear Infirmary with a diagnosis of keratoconus were reviewed. Eligible patients were seen for an office visit between January 1, 2009 and January 31, 2010 and a separate review was conducted between January 1, 2019 and January 31, 2020. The study was approved by the University of Illinois at Chicago Institutional Review Board.

Patients with a final contact lens prescription with follow up exams scheduled for 6 months or further were included. Demographics, corneal curvature, best-corrected visual acuity with manifest refraction, best-corrected visual acuity with contact lens correction and type of corrective lens prescribed were recorded for the right eye only. If the right eye had previously undergone corneal transplantation, left eye data was collected. Analyses were based on a single eye per individual in order to allow standard statistical methods to be utilized without having to make allowances due to between eye correlation.¹⁴ Snellen visual acuities were converted to LogMAR for analysis. Severity of corneal irregularity was categorized using mean keratometry readings using the Amsler-Krumeich classification stages I-IV.¹⁵ Data was not available for all parameters for each patient.

Descriptive statistics are reported. In addition, two-sample t-tests and chi-square tests were performed to examine changes in visual acuity, keratometry, demographics, and final lens type between 2010 and 2020. For analysis of change in visual acuity, only eyes that had best corrected visual acuity with both manifest refraction and contact lenses were included. Logistic regression was used to compare corneal severity in 2010 compared to 2020. A P-value<0.05 was considered statistically significant. Data was analyzed using SAS Institute Inc. 2018 (SAS 9.4M6, Cary, NC, USA).

Results:

In the 2010 subset, there were 292 patients (261 right eyes, 31 left eyes due to history of right eye corneal transplant) identified. Mean patient age was 43.9 years [13.8, 19-80] (mean [SD, Range]). Patient characteristics are detailed in Table 1. Mean LogMAR visual acuity with manifest refraction was 0.42 [0.33, 0-1.3) improving to 0.19 [0.18, 0- 1.3; P=<.01] with contact lens correction (Table 2). In the 2020 subset, there were 217 patients (195 right eyes, 22 left eyes due to history of right eye corneal transplant) identified with a mean age of 49.3 [14.6, 16- 81] (Table 2). In 2010, 69% of patients were using corneal GP, 16% soft toric, 13% hybrid, 2% soft sphere and there were no SL wearers. In 2020, 60% were using corneal GP, 22% SL, 12% soft toric, 5% hybrid and 1% soft sphere. LogMAR visual acuity with manifest refraction was 0.35 [0.33, 0- 1.6] with improvement to 0.13 [0.14, 0- 0.60; P=<.01] with contact lenses. Despite steeper mean keratometry measurements in the 2020 subset compared to the 2010 subset (50.7±7.4 (38.5-84.5) versus 48.7±5.2 (34.5-69.9); P<.01)), best corrected vision with manifest refraction and contact lenses were better in the 2020 subset (P<0.01 and P<0.01; Table 2).

Table 1:

Demographics of patients with keratoconus using contact lenses in 2010 and 2020 subsets

Variable	2010 (n=292)	2020 (n=217)	Significance
Age (mean ± SD, Range)	43.9 ±13.9 (19-80)	49.3±14.6 (16-81)	P<0.01
Gender n (%)
Female	118 (40.6)	86 (39.6)	P=0.83
Male	173(59.4)	131 (60.4)
Race n (%)
White	127 (43.5)	86 (39.6)
Hispanic	61 (20.9)	51 (23.5)
African American	27 (9.3)	49 (22.6)
Asian	5 (1.7)	2 (0.9)
Other/Unknown	72 (24.6)	29 (13.4)

Table 2:

Ophthalmic characteristics of patients with keratoconus in 2010 and 2020 subsets

	2010	2020
Spectacle Best Corrected Visual Acuity (LogMAR) mean ± SD (Range)	0.42±0.33 (0-1.3, n=286)	0.35 ±0.33 (0-1.6; n=175)	P=0.018
Best Corrected Visual Acuity with Contact Lens and by Lens Type	0.19±0.18 (0-1.3)	0.13±0.14 (0-0.6)	P<0.01
Soft Sphere	0.28±0.37 (n=6)	0±0 (n=2)
Soft Toric	0.16±0.15 (n=46)	0.08±0.12 (n=26)
Corneal Gas Permeable	0.21 ±0.18 (n=197)	0.13 ±0.14 (n=99)
Hybrid	0.15±0.13 (n=37)	0.12±0.13 (n=11)
Scleral	---	0.16 ±0.16 (n=37)
Mean Keratometry (D)	48.7±5.2 (34.5-69.9) n=259	50.7±7.4 (38.5-84.5) n=208	P=0.09
Flat Keratometry (D)	48.0±5.2 (28.6-71.0) n=259	48.8±7.4 (34.4-81.0) n=208	P=0.16
Steep Keratometry (D)	49.4 ±6.0 (37.6-69.4) n=259	52.6 ±8.1 (37.8-88.0) n=208	P<0.01
Amsler-Krumeich Classification, n (%)	131 (50.6)	93 (44.7)	P=0.016
Stage I
Stage II	83 (32.1)	55 (26.4)
Stage III	10 (3.9)	17 (8.2)
Stage IV	35 (13.5)	43 (20.7)

Type of contact lens prescribed based on Amsler-Krumeich classification are shown for the 2010 and 2020 subsets in Figure 1. Of 202 patients using corneal GP lenses in 2010, 26 (12.8%) were prescribed a piggyback system. In the 2020 group, 22 (16.9%) of 130 patients using corneal GP lenses were using a piggyback system. There were no patients using SL in 2010 and 48 patients wearing SLs in 2020. More than half (56.3%) of these patients using SLs had been refit from corneal GP lenses. The mean keratometry measurement in patients using SLs was 53.0 diopters [9.9, 42.1-84.5] which was steeper than the mean keratometry measurement of 46.6 diopters in patient’s using all other lens types in 2010 and 2020 [3.9, 40.9-57.9; P<0.01]; Table 3). Of 35 patients with stage IV keratoconus in 2010, 33 (94%) were fit in corneal GP and 2 in hybrid lenses. In the 2020 subset of 43 patients with stage IV severe keratoconus, 27 (62.8%) were fit in corneal GP, 2 soft toric, one hybrid and 13 SL (30.2%). Mean keratometry in all corneal GP wearers was less steep compared to those using SLs (50.18 vs. 53.01, P<0.01; Table 3). Mean keratometry of all patients categorized in the severe stage IV category was 66.6D for SL wearers versus 59.7 D for corneal GP wearers (P<0.01).

Figure 1.

Type of Contact Lens used by patients in 2010 and 2020 groups. Mode of contact lens is illustrated for the 2010 and 2020 subsets of patients with keratoconus. Severity of keratoconus is illustrated using Amsler-Krumeich severity classification stages I, II, III and IV.

Table 3:

Mean and steep keratometry measurements by contact lens type in 2010 and 2020 (Diopters)

	2010			2020
	n	Mean ± SD	Steep ± SD	n	Mean ± SD	Steep ± SD
Soft Sphere	6	44.50±3.31	45.37 ±3.98	2	43.74±2.91 (n=2)	44.74±3.97
Soft Toric	41	45.07±2.76	45.27±3.67	26	47.16±4.41(n=26)	49.29 ±5.61
Corneal Gas Permeable	182	49.75±5.46	50.52±6.16	123	50.82±6.74	52.37 ±7.24
Hybrid	30	47.95±3.94	48.69±4.94	10	49.36±4.62	51.33 ±4.49
Scleral	0	--	--	47	53.01±9.90	55.67±10.77

Discussion:

In this study, contact lens prescribing trends for patients with keratoconus in 2010 are compared to 2020 at an academic medical center. The majority of patients were prescribed corneal GP lenses although there was a decrease from 69% of patients using corneal GP lenses in 2010 to 60% of patients in 2020. Most notably, in our cohort, the percentage of patients using SLs increased from 0% to 22% from 2010 to 2020. A 2020 report on international contact lens prescribing trends showed that while the overall rate of gas GP lens prescribing has remained stable at 13%, scleral lens prescribing which were negligible 15 to 20 years ago has increased to now account for about 3% of all GP lenses prescribed.¹⁷ In this cohort, SL wearers had the steepest mean keratometry readings compared to patients prescribed other lens types and yet maintained a mean visual acuity of better than 20/30. This improvement in visual acuity is consistent with a larger percentage of patients in corneal GP, SL and hybrid lenses in the 2020 group compared to 2010. However, best corrected visual acuity improved for soft toric, hybrid and GP modalities and so overall improvement in visual acuity cannot be solely attributed to SL. It is notable that there was better visual acuity achieved despite an increase in mean keratometry and increase in percentage of patients classified as Stage IV keratoconus.

Individuals with keratoconus typically rely on contact lenses to provide optimal visual acuity and function. While corneal GP lenses have historically been the lens of choice of practitioners, this trend has been changing with the reemergence of SLs. In this study, corneal GP lenses continued to be the most frequent type of contact lens used, though SL use increased from zero in 2010 to nearly one in every five patients in 2020. This is comparable to a 2013 cross sectional study of 244 patient with keratoconus in which 68% were using cornel GP lenses.¹⁶ This trend is also consistent with a SCOPE study group survey of SL prescribers that reported over half of respondents fit their first patient with SLs between 2010 and 2015.¹¹ The SCOPE study group also reported that for providers graduating after 2009, there was an increase in the amount of new graduates trained in SL fitting and an increase in utilization of SLs outside of hospital and tertiary care settings.¹¹ Contact lens educators report they have all incorporated scleral lens education into their curriculum and estimate students complete an estimated 99 soft, 20 corneal GP, 18 scleral, 11 orthokeratology and 3.6 hybrid contact lens evaluations during their training.¹⁸ It will be interesting to follow trends and see if new grads opt to utilize SL rather than corneal GP lenses in the future. Patients using corneal GP lenses may experience issues with increased wear time such as lens awareness, lens displacement or loss, increased dryness, or corneal scarring, particularly in patients with advanced or peripheral ectasia.^19–22 A study by Wu et al showed that although individuals with mild and moderate keratoconus wearing corneal GP lenses have similar vision related quality of life scores, when steep keratometric values are worse than 52 diopters, there is a significantly poorer vision related quality of life and reduced daily contact lens wear time.¹⁹ For patients that are unable to tolerate corneal GP lenses, a soft lens can be fit under the corneal GP as a piggyback system which can relieve the mechanical interaction and improve patient comfort.²² Although the specific reason for use of each lens type were not recorded in this study, piggyback systems were utilized in ~15% of patients using corneal GP lenses indicative of likely fit or comfort issues. The authors maximize corneal GP options by fitting patients of all severities with diagnostic lenses, customizing corneal GP peripheral curves and utilizing piggyback systems likely increasing the proportion in piggyback lenses. While previously reserved for patients with the most severe keratoconus, SLs are now more readily available to all practitioners, with the availability of improved materials and multiple manufacturers offering highly customizable and more user-friendly designs.^{4, 8, 9}

Not surprisingly, SL wearers had more advanced keratoconus compared to patients prescribed other lens types at this academic medical center. A survey of patients with keratoconus by the National Keratoconus Foundation and the SCOPE Study group showed SL wearers had higher satisfaction with both vision and comfort compared to patients wearing corneal GP lenses.²³ SLs are filled with a preservative free solution, vault over the corneal surface, and rest on the conjunctiva. The absence of corneal-lens interaction and the continued lubrication has been shown to improve comfort, dryness and quality of life in patients that have been intolerant to other contact lens modalities.⁴ In addition, hybrid lenses which have a rigid gas permeable center with a soft periphery or skirt, have also been shown to improve comfort when compared to corneal GPs. Hybrid lenses can be made in keratoconus specific designs and have a high oxygen permeability (Dk) silicone hydrogel skirt to address prior issues with lens tightening and hypoxic-related corneal neovascularization that was previously seen with low Dk hydrogel skirts.²⁴ Despite availability of high Dk hybrid lens options, hybrid lens prescription has decreased in this cohort perhaps in favor of SLs. While SLs may provide better comfort in particular for patients with coexisting dry eye disease, increased cost may be a concern. Annual out of pocket costs for patients related to contact lenses was less than $1000 in 60% of corneal GP wearers compared to only 41% of SL wearers.²³

The retrospective design allows for an overview of clinical practice and changes over time; however, not all data was available for each patient. This study is limited by study design and no identifiers were recorded that would allow direct comparison between 2010 and 2020 patients. Additionally, it was unknown which previous lens types had been tried or why the final lens type was selected for the patient by the practitioner. There was a decrease in total number of patients with keratoconus identified during the study period. It is possible that this clinical practice has shifted towards the management of ocular surface disease and/or patients are receiving more community-based care for corneal irregularity. A previous study at this institution between 2010 and 2015 found that the majority (71%) were fit with SLs due to ocular surface disease and only 29% were fit due to corneal irregularity as the primary diagnosis.²⁵ This differs from a SCOPE study of SL prescribers, in which corneal irregularity was the most common indication for SL fitting accounting for an estimated 74% of all SL evaluations.¹¹ There was a decrease in patients seen with stages 1 and 2 early keratoconus and an increase in individuals with more advanced disease in 2020. This suggests more advanced cases may be referred to this tertiary care center and it is also possible that surgeons may be referring patients for scleral lenses rather than recommending surgical intervention. These findings cannot be generalized to patients who have previously undergone corneal transplantation as they were excluded from this study. Future prospective studies are needed to focus on patient centric issues such as care burden, including expenses and time spent daily handling lenses, as well as co-existing age related dry eye and overall comfort.

This study highlights changes that have occurred with the management of patients with keratoconus over the past 10 years. Though SL use in patients with keratoconus increased from zero to almost a quarter of lens fits between 2010 and 2020, corneal GP lenses continue to be the primary lens of choice at our facility. SL fittings should be considered for patients prior to considering corneal transplantation.