Abstract
PURPOSE:
The purpose of the study is to evaluate the visual outcomes and improvement in quality of life (QOL) of patients with keratoconus with scleral lenses.
METHODS:
In this prospective study, 14 patients (28 eyes) with bilateral keratoconus were fitted with scleral lenses (McAsfeer 16.00 mm) in Pune city, Maharashtra, India. Uncorrected visual acuity (VA), best spectacle-corrected VA, and VA with scleral lenses were evaluated. The patients were given the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25) for judging the QOL, before and after using scleral lenses for 3 months.
RESULTS:
The mean uncorrected VA of the 14 patients with a mean age of 28.64 ± 6.57 years was 1.18 ± 0.19 logMAR. Best spectacle-corrected high-contrast VA improved from 0.47 ± 0.25 logMAR to 0.03 ± 0.07 logMAR with scleral lenses (P < 0.001). Best spectacle-corrected low-contrast VA improved from 0.68 ± 0.22 logMAR to 00.47 ± 0.10 logMAR with scleral lenses (P < 0.001). Along with the increase in overall median scores on the NEI VFQ-25 from 1735 to 2930 points (P < 0.001), the distance and near activities (P < 0.001), vision-specific mental health (P < 0.002), social functioning (P < 0.004), and driving (P < 0.005) improved after using scleral lenses for 3 months.
CONCLUSION:
Scleral lenses can be an effective and safe management option for patients with keratoconus leading to an improved vision and QOL.
Keywords: High-contrast visual acuity, keratoconus, low-contrast visual acuity, National Eye Institute Visual Function Questionnaire-25, quality of life, scleral lenses
INTRODUCTION
The cornea is responsible for the majority of the total refractive power of the eyeball. A smooth regular refracting surface is thus important to form a clear image on the retina. Visual acuity (VA) and contrast sensitivity are reduced in the patients with corneal ectasias because of high and/or irregular astigmatism.
Keratoconus is a bilateral and asymmetric ocular disease which results in progressive thinning and steepening of the cornea leading to irregular astigmatism and decreased visual acuity. Corneal thinning occurs in the central or paracentral cornea, most commonly infero-temporally. Traditionally, keratoconus has been described as a noninflammatory disease; however, several studies have reported associations with significant alterations in inflammatory mediators, indicating that keratoconic eyes often experience some form of ocular inflammation. Although a bilateral condition, one eye is typically more severely affected than the other.[1] A study done by Lee et al., on the basis of computerized corneal topography, it was found that, in a group of 21 patients with clinically diagnosed unilateral keratoconus, computerized corneal topographic analysis identified 14 (67%) patients with bilateral keratoconus and seven (33%) patients with true unilateral keratoconus.[2] Results from a study by Holland et al. suggest that the incidence of “unilateral” keratoconus is very low (1.83%).[3] Patients initially diagnosed with unilateral keratoconus, if observed for a sufficient period, commonly had signs of keratoconus develop in the opposite eye.[3] Hence, it can be concluded that both eyes are affected eventually, at least as seen on topographical imaging, in almost all cases. Because of this, there is impairment of vision due to progressive myopia and astigmatism.[4]
“Forme fruste” keratoconus and/or low postablation corneal thickness are the major risk factors to develop corneal ectasia secondary to laser-assisted in situ keratomileusis (LASIK).[5] Some late complications of penetrating keratoplasty include astigmatism and recurrence of underlying disease.[5]
The management of patients with mild corneal ectasias consists primarily of providing optical correction to maximize visual function. In very mild or early conditions, spectacle correction or standard soft contact lenses or corneal rigid gas permeable contact lenses may provide adequate vision. However, as the corneal ectasia progresses with the progression of keratoconus, it gives rise to complex optical aberrations in that eye. Vision may be limited since glasses do not correct irregular astigmatism. Optical devices are the management option of choice in the mild stages with surgery being a last resort. Other contact lens options for the management of corneal ectasias are Rose K designs, piggyback lens systems, hybrid lens designs, and scleral contact lenses. The type of contact lenses prescribed depends on the stage of keratoconus.[6]
Although both corneal rigid gas permeable and scleral contact lenses are indicated for ectatic corneal disorders, traditional corneal rigid gas permeable contact lens may not be appropriate for the advanced cases of markedly irregular corneal surfaces. Corneal irregularities may lead to rigid gas permeable contact lens decentration, dislocation, and discomfort from inadequate contact lens fitting patterns. In addition, rigid gas permeable contact lens may be associated with an increased risk of corneal scarring in patients with keratoconus.[7]
In 2019, the Scleral Lens Education Society adopted a new perspective and defined scleral lenses as “a lens fitted to vault over the entire cornea, including the limbus, and to land on conjunctiva overlying the sclera.” As they rest on the less sensitive sclera, these lenses are suitable for various corneal surface pathologies with minimum lens awareness.[8] They offer a large space between the cornea and the contact lenses. Correcting the irregular cornea to restore vision is the main indication for fitting scleral lenses. They are used for visual rehabilitation in patients with irregular corneal surfaces.[9] The largest segment within this category is corneal ectasia, which can be subdivided into two groups. First is the primary corneal ectasia group, which includes conditions such as keratoconus, keratoglobus, and pellucid marginal degeneration. The secondary ectasia group consists of postrefractive surgery, including LASIK, Post-laser assisted epithelial keratoplasty (LASEK), post-photorefractive kerectomy (PRK), and postcorneal trauma.
The constant tear reservoir between the posterior surface of the scleral contact lenses and the irregular corneal surface is able to neutralize most irregular astigmatism and aberrations. The fluid reservoir between the posterior lens surface and anterior cornea can neutralize irregular astigmatism of the anterior surface.[10] Conventional scleral lenses mask higher-order aberrations between 60% and 65%[11,12] through (1) approximate refractive index matching of the postlens tear layer and the cornea and (2) by providing a new, well-formed optical first refracting surface for light entering the eye.[13]
Vision impairment is associated with a reduced QOL, which is a “complex trait that encompasses vision functioning, symptoms, emotional well-being, social relationships, concerns, and convenience as they are affected by vision.”[13,14] Numerous studies have shown that vision impairment is often associated with various negative health outcomes and poor QOL.[13,15,16]
Especially in these situations, the use of the Visual Function Questionnaire-25 (VFQ-25) can be considered. Accessing the QOL of such patients having chronic eye diseases such as keratoconus is important because any self-reported problem related to vision may constitute a QOL issue.
METHODS
This prospective study, after getting approved by the Institutional Ethics Committee, was carried out in Pune city, Maharashtra, India, for the duration of 5 months.
The patients diagnosed with bilateral keratoconus and referred to the clinic for trials of scleral lenses were included in the study.
Each patient meeting the inclusion criteria was informed about the purpose of the study and a well-informed written consent for participation was obtained from them before participation.
First visit
All 14 patients underwent thorough standard optometric examination and the contact lens pre-fitting evaluation.
Uncorrected VA and best-corrected VA with spectacles were evaluated with “High and Low Contrast Bailey Lovie (HCBL and LCBL) logMAR charts (HCBL [90%], LCBL [8%–10%])”[17] at testing distance of 3 m, with undilated pupil in standard room illumination. The VA was denoted in logMAR value. Example: LogMAR 0.00 (or) 10/10 (or) 20/20 equivalent.
The patients were given the self-administered National Eye Institute (NEI) VFQ-25 for judging the QOL before using scleral lenses for the assessment of their general health and vision, difficulty with activities, and other subscales.
The NEI VFQ-25 generated the following vision-targeted subscales: global vision rating, difficulty with near vision activities, difficulty with distance vision activities, limitations in social functioning due to vision, role limitations due to vision, dependency on others due to vision, mental health symptoms due to vision, driving difficulties, limitations with peripheral and color vision, and ocular pain. This vision-targeted questionnaire measures the influence of visual disability and visual symptoms on generic health domains such as emotional well-being and social functioning, in addition to task-oriented domains related to daily visual functioning.
Scleral lenses of McAsfeer (Silver Line Laboratories) 16.0 mm were fitted to the patients after giving trials where the lens was filled with saline (0.9% sodium chloride) solution. Between 250 and 350 microns was considered optimal central clearance immediately after insertion, leaving at least 150 microns final clearance even after an average settling of 100 microns.[18] [Figure 1] Good landing zone fitting was considered as an ideal fitting range for ordering the final scleral lens parameters.
Figure 1.
Assessment of the central clearance
Second visit
The expected central clearance of the ordered scleral lenses was assessed. Furthermore, landing zone was assessed for any compression or impingement. The wearing modality, care and maintenance, and the application of the scleral lenses were explained and illustrated to the patient in detail. The scleral lenses were then dispensed to the patients.
Follow-up visit after 3 months
Both high- and low-contrast visual acuities with scleral lenses were evaluated using the same logMAR charts.
The subjects were once again given the self-administered NEI VFQ-25 for judging the QOL after using scleral lenses.
The QOL of the patients fitted with scleral lenses in both the eyes was assessed. The patients affected in both eyes would give better results rather than patients using scleral lenses in only one eye.
The comfortable wearing time (in hours) was noted subjectively.
The symptoms such as redness, itching, tearing, photophobia, pain, unusual eye secretions, haloes, burning, blur vision, and compliance of the patients using the scleral contact lenses were noted subjectively using a Likert scale.
Statistical analysis
The data were analyzed using SPSS (the Statistical Package for the Social Sciences) version 28 software.
The paired t-test was used to compare the uncorrected VA, best-corrected VA with spectacles, and VA with scleral lenses with high-contrast and low-contrast logMAR VA chart.
The self-administered NEI VFQ-25 questionnaire for judging the before and after QOL of the patients using scleral lenses was analyzed using the Wilcoxon signed-ranked test.
P < 0.05 was considered to be clinically significant.
RESULTS
Out of 14 keratoconus patients, 7 (50%) were male and 7 (50%) were female. Nine (64.28%) of them were in the age group of 21–30 years, four (28.58%) were in the age group of 31–40 years, and one (7.14%) patient was in the age group of 41–50 years.
The mean uncorrected VA was 1.18 ± 0.19 logMAR. Best spectacle-corrected high-contract VA improved from 0.47 ± 0.25 logMAR to 0.03 ± 0.07 logMAR with scleral lenses (P < 0.001). Best spectacle-corrected low-contract VA improved from 0.68 ± 0.22 logMAR to 0.47 ± 0.10 logMAR with scleral lenses (P < 0.001) [Table 1].
Table 1.
Comparison of unaided visual acuity high-contrast visual acuity and low-contrast visual acuity with spectacles and scleral lenses in both eyes
| BE | VA (logMAR) |
|||||
|---|---|---|---|---|---|---|
| Minimum | Maximum | Mean±SD | ||||
| Unaided VA | 0.8 | 1.4 | 1.18±0.19 | |||
| HCVA with spectacles | 0.2 | 1 | 0.47±0.25 | |||
| HCVA with scleral lenses | 0 | 0.3 | 0.03±0.07 | |||
| LCVA with spectacles | 0.4 | 1.3 | 0.68±0.22 | |||
| LCVA with scleral lenses | 0.3 | 0.7 | 0.47±0.1 | |||
BE: Both eyes, VA: Visual acuity, HCVA: High-contrast VA, LCVA: Low-contrast VA, SD: Standard deviation, logMAR: Logarithm of the minimum angle of resolution
The overall median score of the QOL of the patients increased from 1735 to 2930 points after 3 months of scleral lens wear, which showed clinically and statistically significant improvement (P < 0.001) [Figure 2].
Figure 2.
Improvement in overall National Eye Institute Visual Function Questionnaire-25 median scores after 3 months of sclera lens wear
The median scores for distance and near activities of the patients improved from 137.5 to 287.5 (P < 0.001) and from 175 to 300 (P < 0.001), respectively, whereas the general vision improved from 40 to 80 (P < 0.002). The median scores for vision-specific mental health improved from 137.5 to 300 (P < 0.002) while vision-specific social functioning improved from 150 to 200 (P < 0.004). The median scores regarding the driving subscale reported an improvement from 125 to 250 points (P < 0.005). The change of median scores of 175–250 regarding vision-specific dependency on others was reported (P < 0.012). The patients did not experience any statistical improvement in color vision (P < 0.038) [Table 2 and Figure 3].
Table 2.
National Eye Institute Visual Function Questionnaire-25 subscales media scores before and after using scleral lenses for 3 months
| NEI VFQ-25 subscales | NEI VFQ-25 subscale median scores before and after 3 months of scleral lens wear |
P | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Pre | SD | Post | SD | |||||||
| Overall scores | 1735 | 520.85 | 2930 | 390.55 | 0.001 | |||||
| Distance activities | 137.5 | 43.85 | 287.5 | 41.27 | 0.001 | |||||
| Near activities | 175 | 69.14 | 300 | 28.04 | 0.001 | |||||
| Vision-specific mental health | 137.5 | 78.73 | 300 | 87.39 | 0.002 | |||||
| General vision | 40 | 21.79 | 80 | 9.49 | 0.002 | |||||
| Peripheral vision | 50 | 25.41 | 100 | 15.83 | 0.004 | |||||
| Vision-specific social functioning | 150 | 47.64 | 200 | 25.41 | 0.004 | |||||
| Driving | 125 | 85.18 | 250 | 93.78 | 0.005 | |||||
| Ocular pain | 125 | 43.54 | 150 | 35.36 | 0.005 | |||||
| General health | 50 | 24.86 | 50 | 18.99 | 0.015 | |||||
| Vision-specific dependency | 175 | 97.16 | 250 | 47.75 | 0.012 | |||||
| Vision-specific role difficulties | 100 | 51.39 | 150 | 48.04 | 0.014 | |||||
| Color vision | 100 | 25.21 | 100 | 9.08 | 0.038 | |||||
NEI VFQ-25: National Eye Institute Visual Function Questionnaire-25, SD: Standard deviation
Figure 3.
National Eye Institute Visual Function Questionnaire-25 subscale median scores before and after using sclera lenses for 3 months. NEI VFQ-25: National Eye Institute Visual Function Questionnaire-25
The patients were wearing the scleral lenses for an average time of 9.5 ± 3.08 (range of 8–16) h/day. The patients were comfortable wearing the scleral lenses with a mean average rating of 7.5 ± 1.16 on the scale of 1–10.
The patients showed good scleral lens compliance reporting some minor nonthreating symptoms such as redness, itching, tearing, photophobia, pain, unusual eye secretions, haloes, burning, and blur vision for distance and near.
DISCUSSION
In this study, the patients with keratoconus, who were unable to achieve adequate visual outcomes with otherwise traditional optical correction methods such as spectacles and corneal rigid gas permeable corneal contact lenses, were fitted with scleral lenses to assess the improvement in visual outcome and QOL.
The patients were fitted with SPOT (®) scleral lenses in a study done by Picot C et al.[19] and Yan P et al. used either Maxim 5R, Maxim 7, or Maxim 7 × 11 scleral lenses[20] and Kim et al. used Mini-Scleral Design (MSD) scleral lenses.[21] In the previous studies carried out in India, Rathi et al. and Arumugam et al. used PROSE scleral lenses.[22,23] In this study, the patients were fitted with McAsfeer (Silver Line Laboratories) 16.0-mm scleral lenses.
In a study done by Kim et al. in Korea, the mean log MAR VA was improved from 0.85 ± 0.78 with glasses to 0.10 ± 0.11 with scleral lenses.[21] Yan P et al. also assessed the improvement in the VA from 0.3 logMAR before scleral lenses to 0.05 logMAR with scleral lenses.[24] Similar to these results, in the present study, best spectacle-corrected high-contract VA improved from 0.47 ± 0.25 logMAR to 0.03 ± 0.07 logMAR with scleral lenses, representing a clinically and statistically significant improvement.
Unlike previous published studies, this study has tested the low-contrast VA too along with the high contrast, as the low contrast is an essential part of the visual capability. Best spectacle-corrected low-contrast VA improved from 0.68 ± 0.22 logMAR to 0.47 ± 0.10 logMAR with scleral lenses.
While keratoconus is a chronic condition that rarely results in blindness, the results of the NEI-VFQ suggest that its effect on vision-specific QOL is worse than expected based on the condition’s relatively low prevalence and clinical severity.[25]
Here, in this study, an English version of the NEI VFQ-25 was used, whereas Picot C et al. used a French version[19] and Baali M et al. used the Moroccan version to assess the QOL of the patients fitted with scleral lenses in one or both eyes.[26]
In this study, the overall median scores on the NEI VFQ-25 after using scleral lenses for 3 months were higher than that of before, implying better performance, which is clinically significant (P < 0.001). This is similar to the previous study done by Baali M et al. where the average scores on the NEI-VFQ 25 of the patients after fitting scleral lenses were significantly higher.[26]
The NEI VFQ-25 subscales are grouped by theme. Considering the subscales of the NEI VFQ-25, patients experienced a drastic improvement with distance (P < 0.001) and near (P < 0.001) activities. There was a significant improvement in vision-specific mental health (P < 0.002) and social functioning (P < 0.004). The difficulty with driving was significantly reduced too (P < 0.005). Similar to these results, a study done by Kreps et al. showed significant improved results for both visual functioning and socioemotional scales after scleral lens fitting.[27] Similar to these results, Kymes et al. in their multicenter 7-year follow-up study found that dependency of the Collaborative Longitudinal Evaluation of Keratoconus Study participants declined considerably, and mental health improved.[28] In a study done by Cagliari et al., variables related to endothelial morphology and pachymetry values did not change significantly over time from the above study.[29]
Ortenberg et al. have stated in their study that one of the important factors in knowing the success rate of the scleral lenses is the wearing time.[30] In this study, the patients used these scleral lenses for a mean average of 9.5 ± 3.08 h/day (range 8–16).
CONCLUSION
This study concludes that there was an improvement in both high- and low-contrast VA with scleral lens wear. These 3 months of scleral lens wear led to a significant improvement in the QOL of the participants. This study also found out that participants with keratoconus were comfortable wearing the scleral lenses.
The more number of participants can be included in future studies and they can be observed for a longer period of time for their QOL assessment, to confirm the results of this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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