To evaluate changes in corneal topography indices after corneal collagen crosslinking (CXL) in patients with keratoconus and corneal ectasia and analyze associations of these changes with visual acuity. Cornea and refractive surgery subspecialty practice. Prospective randomized controlled clinical trial. Corneal collagen crosslinking was performed in eyes with keratoconus or ectasia. Quantitative descriptors of corneal topography were measured with the Pentacam topographer and included 7 indices: index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, minimum radius of curvature, index of height asymmetry, and index of height decentration. Follow-up was 1 year. The study comprised 71 eyes, 49 with keratoconus and 22 with post-LASIK ectasia. In the entire patient cohort, there were significant improvements in the index of surface variance, index of vertical asymmetry, keratoconus index, and minimum radius of curvature at 1 year compared with baseline (all P < .001). There were no significant differences between the keratoconus and ectasia subgroups. Improvements in postoperative indices were not correlated with changes in corrected or uncorrected distance visual acuity. There were improvements in 4 of 7 topography indices 1 year after CXL, suggesting an overall improvement in corneal shape. However, no significant correlation was found between the changes in individual topography indices and changes in visual acuity after CXL. Copyright © 2011. Published by Elsevier Inc.