Comparative Analysis of Refractive and Topographic Changes in Early and Advanced Keratoconic Eyes Undergoing Corneal Collagen Crosslinking

PURPOSE: To compare the refractive and topographic changes at 1 year in eyes with early and advanced keratoconus undergoing corneal collagen crosslinking (CXL). A prospective, nonrandomized comparative clinical intervention study. METHODS: Thirty eyes of patients with keratoconus underwent CXL. They were divided into 2 groups based on their mean central keratometry: group A [mean central K ≤ 53 diopters (D)] and group B (mean central K > 53 D). Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), refraction, topography, pachymetry, and endothelial cell counts were evaluated at baseline and at 1, 3, 6, and 12 months of follow-up. RESULTS: The mean baseline logarithm of the minimum angle of resolution (logMAR) UCVA and logMAR BCVA in group A was 1.007 ± 0.30 and 0.566 ± 0.21, respectively. The values improved to 0.727 ± 0.29 (P = 0.001) and 0.306 ± 0.15 (P = 0.001) at 1-year post CXL. The mean baseline logMAR UCVA and logMAR BCVA in group B were 1.040 ± 0.24 and 0.641 ± 0.25, respectively. It changed to 0.953 ± 0.26 (P = 0.054) and 0.633 ± 0.27 (P = 0.891) at 1 year. The improvement in the UCVA and BCVA was statistically significant in group A as compared with that in group B. The mean baseline flattest, steepest, central, and apical keratometry in group A were 48.7 ± 2.5 D, 54.9 ± 3.3 D, 49.5 ± 1.4 D, and 57.3 ± 2.3 D, respectively. At 12 months, the values changed to 47.8 ± 2.4 D, 54.1 ± 3.0 D, 48.8 ± 1.8 D, and 56.2 ± 2.7 D, the change being statistically significant for mean flat and apical K only (P < 0.05). All the 4 indices did not show any statistically significant difference at 12 months in group B (P > 0.05). CONCLUSIONS: Corneal CXL is more effective in improving the refractive and topographical parameters at 1 year when it is performed early in the course of the disease.