Corneal Cross-linking for Progressive Keratoconus in Patients Older Than 40 Years: Long-term Follow-up

PURPOSE: To assess the long-term efficacy and safety of epithelium-off corneal cross-linking according to the standard (Dresden) protocol (S-CXL) in patients with progressive keratoconus older than 40 years. METHODS: Seventy-six eyes of 64 patients with a mean age of 46.4 +/- 5.2 years were included. At baseline and after 6, 12, 24, 36, 48, 60, 72, 84, and more than 96 months (when available) after S-CXL, all patients were assessed with distance-corrected visual acuity (DCVA) and corneal topography and tomography with Pentacam HR (OCULUS Optikgerate GmbH). A generalized linear model was used to compare the groups. Outcome measures were maximum keratometry, thinnest point, coma, spherical, and higher order aberrations, and ABC values. Fixed and random factors were age, gender, atopy, laterality, and group. RESULTS: The mean follow-up time was 62.1 +/- 40.1 months (range: 12 to 144 months). The main outcome of the study was the evidence that S-CXL was able to safely stop the progression of keratoconus in all patients with none requiring repeat CXL. The generalized linear model analysis showed no significant change in DCVA over time (P = 1.000), but atopy was negatively associated with DCVA (P = .030, B = -0.69). The generalized linear model also showed that CXL was able to induce a significant flattening demonstrated as reduction of maximum keratometry (P = .001, B = -0.35) and A value (P = .001, B = -0.015) of the ABC display. Similarly, coma aberration was reduced over time (P = .006, B = -0.005). CONCLUSIONS: S-CXL was confirmed to be a safe and effective treatment for progressive keratoconus even after the age of 40 years, inducing a significant flattening of the cone.