Effects of Soft Toric, Rigid Gas-Permeable, and Mini-Scleral Lenses on Corneal Microstructure Using Confocal Microscopy

Objective: To determine effects of wearing soft toric silicone hydrogel, rigid gas-permeable (RGP), and mini-scleral lenses on corneal microstructure using confocal microscopy. Method: A prospective cohort study was conducted on 33 neophyte patients fitted with contact lenses (avg. age: 26 +/- 7 years) in the tertiary eye center. Patients were instructed to wear soft toric silicone hydrogel, RGP, or mini-scleral lenses based on clinical diagnoses. Inclusion criteria were age greater than 18 years and best-corrected visual acuity >= 3/10. Patients with a history of eye-involving systemic diseases were excluded. Baseline examinations included log of minimal angle of resolution visual acuity (Early Treatment Diabetic Retinopathy Study chart), refraction, slit-lamp, and fundoscopy. Confocal microscopy was used to measure subbasal nerve (SBN) density (mm/mm(2)), keratocyte cell density (cells/mm(2)), basal epithelial cell density (cells/mm(2)), and endothelial cell density (cells/mm(2)). Data were gathered on the first and follow-up visits. The follow-up visit happened after 6 months when the subjects had stopped wearing contact lenses for 12 hr. Comparative analysis was conducted within each group using the paired t test. Results: The changes in visual acuity, SBN, and keratocyte cell density were insignificant after 6 months of wearing lenses in all three groups. The basal epithelial cell density significantly decreased (P<0.05) in RGP and mini-scleral groups. In addition, the endothelial cell density decreased significantly (P<0.05) in the RGP group. No significant changes were detected in soft toric silicone hydrogel lens wearers. Conclusions: Soft toric silicone hydrogel lenses seemed to have the least impact on the corneal cellular microstructure for a wear period of 6 months, controlling confounding factors of prior cross-sectional investigations. The coarse (three layers) versus fine (five layers) division of stroma, the repeatability and reproducibility of stromal layers' demarcation, and the cohort size and its diversity in terms of initial corneal diagnoses (particularly in the mini-scleral wearing group) can potentially influence the outcomes, and their impact remains to be further investigated.