Comparison of visual acuity outcomes and topographic differences: Rigid gas-permeable lens versus mini-scleral lenses for moderate-to-severe keratoconus

Abstract: PURPOSE: The purpose of the study was to compare the visual outcomes of small-diameter rigid gas-permeable (RGP) lenses and mini-scleral lenses (MScL) in patients with moderate-to-severe keratoconus (KC) and to evaluate the utility of corneal topographic indices in guiding lens selection. MATERIALS AND METHODS: This retrospective study included 36 eyes from 28 patients with moderate-to-severe KC fitted with either small-diameter RGP lenses or MScLs between May 2017 and January 2024. Data on demographics, daily wearing time, Visual Analog Scale (VAS) scores, best-corrected visual acuity (BCVA), keratometry, cone location, and topographic indices were collected. Multivariate logistic regression and receiver operating characteristic (ROC) curve analyses were performed to identify predictors of lens selection and visual improvement. RESULTS: Thirty eyes from 24 patients were fitted with RGP lenses, and six eyes from four patients with apical scars were fitted with MScLs. Both groups showed significant improvement in BCVA after lens fitting. Compared to the MScL group, the RGP group had significantly lower surface regularity index, cone-to-center distance, and irregular astigmatism index (IAI) but a higher center-surround index (CSI). Keratometry values decreased significantly after RGP lens wear. Lower CSI was associated with greater visual improvement. ROC analysis revealed that higher IAI and more eccentric cones predicted better suitability for MScLs, whereas higher CSI favored RGP lenses. VAS scores were similar between groups, but the RGP group reported longer daily wear time. CONCLUSION: Both small-diameter RGP and MScL lenses significantly improve BCVA in moderate-to-severe KC. MScLs are especially beneficial for patients with apical scarring or highly decentered cones. Cone-to-center distance, IAI, and CSI can aid in optimizing contact lens selection