Mini-scleral lenses significantly improve visual acuity and Quality of Life in keratoconus: Study
Keratoconus is a chronic, progressive corneal ectatic disorder characterized by a conical protrusion of the cornea, thinning of the stroma, and irregular astigmatism. Several refractive surgical techniques are available nowadays; however, specialty contact lenses remain the primary mode of visual correction in these irregular corneas.
Corneal rigid gas permeable (RGP) lenses have been the gold standard lens in patients with keratoconus. Because these lenses bear on the irregular corneal surface and shift with blinking, issues with tolerance and lens instability often occur in keratoconus. Scleral lenses theoretically offer the benefit of bridging the irregular cornea and bearing on the conjunctivoscleral surface, thus eliminating the contact between cornea and lens and consequently improving comfort and stability.
Assessment of the clinical outcome of treatment measures in keratoconus ideally includes not only visual acuity (VA) measures but also patient-reported outcomes in vision related quality of life. High-contrast VA testing has shown to be more variable in keratoconus compared with normal eyes, and the impact of keratoconus on visual functioning has been demonstrated to be disproportionate to the measured high contrast VA.
Reports on the effect of scleral lenses on vision-related quality of life have mainly focused on the Boston Sight Prosthetic Replacement of Ocular Surface Ecosystem (PROSE) device and typically involve populations with mixed indications without focusing specifically on patients with keratoconus.
Kreps et al carried out a study to evaluate the clinical outcome of mini-scleral lens fitting in patients with keratoconus and to examine its effects on visual functioning using the improved Rasch adjusted version of the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-39).
This prospective, interventional study examined the effects of mini-scleral lenses on VA and visual functioning in patients with keratoconus. Patients younger than 18 years or with a history of refractive surgery or corneal graft surgery were excluded. Patients were fitted with mini-Misa lenses, Senso mini-scleral lenses, or Zenlens mini-scleral lenses. Outcome measures were scleral lens–corrected VA and vision-related quality of life as assessed with the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-39).
The mini-scleral lenses fitted in these eyes were: mini-Misalenses in 47 eyes (52.8%), mini-Senso lenses in 32 (36%), and Zenlens in 10 eyes (11.2%). Four patients (5 eyes) had undergone corneal cross-linking before mini-scleral lens fitting (<3 mo before lens fitting in all cases).
Eighty-nine eyes of 50 keratoconus patients were included in the study.
Median baseline logarithm of the minimal angle of resolution VA with habitual correction was 0.22 (range 0.02–1.04).
Mini-scleral lens fitting resulted in a statistically significant visual improvement (median 0; P < 0.0001).
At the 6-month follow-up, 11 patients (22%) had abandoned mini-scleral lens wear, primarily because of difficulties with lens handling (7 patients).
Of the 39 patients with continued wear, 33 patients (84.6%) wore their lenses for a daily average of 12 hours. NEI-VFQ scoring in these patients showed significantly improved results for both visual functioning and socioemotional scales after scleral lens fitting (P < 0.0001).
No cases of infectious keratitis or other severe complications related to mini-scleral lens wear were observed in any of the patients.
With mini-scleral lenses, VA improved significantly and 83.1% of fitted eyes achieved a LogMAR VA of at least 0.1, as compared to 31.5% before lens fitting. This excellent visual outcome in mini-scleral lens fitting confirms with previous reports of mini-scleral lens and PROSE fitting in patients with keratoconus.
Daily lens wearing time is another indicator of the performance of contact lenses. In this series, the daily wearing times were comparable with earlier studies reporting wearing times between 8 and 16 h/d in patients with keratoconus fitted with mini-scleral lenses.
The number of lenses and visits needed to successfully complete the fitting process is an indication of the complexity of specialty lens fitting. In this cohort of 89 eyes, only 6 eyes required refitting (2 fitting sessions instead of one), which resulted in a mean of 1.1 lenses ordered per fitted eye.
Quality of-life studies in various pathologies, including keratoconus, have indicated the correlation between vision-related quality-of-life scores and the vision in the better-seeing eye. Findings in this study confirm that visual improvement of the better-seeing eye shows the strongest correlation with improvement in vision related quality of life, with the exception of near activities. Improvement in the worse-seeing eye was significantly associated with improved near activities, which may be accounted for by improving binocular vision.
In conclusion, this study demonstrates excellent clinical outcomes of mini-scleral lens fitting in patients with keratoconus with significant improvement of both VA and vision related quality of life. Troubles with lens insertion and removal remain the principal reason for lens dropout, especially in patients in whom only the worse-seeing eye is fitted.
Source: Kreps et al; Cornea Volume 40, Number 7, July 2021
