Topographic, Corneal Wavefront, and Refractive Outcomes 2 Years After Collagen Crosslinking for Progressive Keratoconus

Abstract

The aim was to report the corneal higher-order aberrations (HOA), the topographic metrics, and the visual and refractive outcomes 2 years after performing collagen crosslinking (CXL) for progressive keratoconus. The correlation among corneal HOAs, topographic metrics, and visual acuity changes was also investigated. This is a prospective case series involving 42 eyes from 32 patients with progressive keratoconus treated with CXL. The main outcomes measured at baseline and 6, 12, and 24 months after treatment were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive changes, topographic data, and corneal aberrations. Two years after CXL treatment, the UDVA (P < 0.001), CDVA (P < 0.001), and spherical equivalent (P = 0.048) improved significantly. The corneal topographic data revealed significant decreases in apical keratometry (P < 0.001), differential keratometry (P = 0.031), and central keratometry (P = 0.003) compared with the baseline measurements. Aberration analyses revealed a significant reduction in coma (P = 0.016), trefoil (P = 0.018), secondary astigmatism (P < 0.001), quatrefoil (P = 0.031), secondary coma (P < 0.001), and secondary trefoil (P = 0.001). Corneal HOA (except quatrefoil) demonstrated a significant correlation with postoperative CDVA; the highest correlations were for coma (rho = 0.703, P < 0.001), secondary astigmatism (rho = 0.519, P = 0.001), and total HOA (rho = 0.487, P = 0.001). However, the corneal HOA changes were not statistically associated with improved visual acuity. After treatment, the reduction in apical keratometry was the only variable that correlated with the improvement in the CDVA (rho = 0.319, P = 0.042). After 2 years, CXL was found to be effective in improving the UDVA, CDVA, topographic metrics, and most corneal HOAs in eyes with progressive keratoconus. A significant reduction was observed in apical keratometry, and this reduction directly correlated with an improvement in visual acuity.