Corneal biomechanical outcome of collagen cross-linking in keratoconic patients evaluated by Corvis ST

Purpose: A 6-month evaluation of the topographic and biomechanical changes induced by corneal collagen cross-linking (CXL) in keratoconic eyes using Pentacam and Corvis ST. Design: Longitudinal prospective case series. Methods: In this study, 67 eyes of 67 patients with progressive keratoconus (KCN) treated with “Epithelium-off” CXL were evaluated. Patients with stages 1 or 2 of KCN and a corneal thickness of at least 400 μm at the thinnest point were included. Standard ophthalmologic examinations were carried out for all patients. The topographic and biomechanical measurements of the cornea were obtained by Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) and Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and 6-month postoperatively. Results: The mean age of the participants was 21.68 ± 4.23 years. There was significant difference in mean spherical equivalent (SE) before and 6 months after CXL. Uncorrected and best corrected visual acuity improved postoperatively, although not statistically significant. The mean and maximum keratometry showed a significant decrease 6 months after CXL (0.93 ± 0.38 D and 1.43 ± 0.62 D, respectively p < 0.001). Among Corvis ST parameters, first applanation length and velocity (AL1 and AV1) showed statistically significant changes. The radius at highest concavity changed significantly (0.13 ± 0.37 mm mean increase after CXL; p < 0.001). A significant increase was observed in stiffness parameter A1 (SP-A1; p < 0.001) and significant decreases were noted in integrated radius (IR) and deformation amplitude ratio (DAR; p < 0.001). Conclusion: Analyzing biomechanical changes after corneal cross-linking can provide basis for efficient KCN treatment. Corvis ST parameters demonstrated changes in corneal biomechanical characteristics indicative of stiffing after CXL.