Corneal cross-linking for progressive keratoconus: Up to 13 years of follow-up

PURPOSE: To assess the long-term efficacy and safety of epithelium-off corneal cross-linking according to the Dresden protocol (S-CXL) in progressive keratoconus. METHODS: Patients treated with S-CXL from April 2006 to January 2010 at Humanitas Clinical and Research Center, Rozzano, Italy, who completed at least 10 years of follow-up were included. Corrected distance visual acuity (CDVA), refraction, and corneal topography and tomography with Pentacam (OCULUS Optikgeräte GmbH) were evaluated at baseline and 10+ years after the procedure. The definition of progression after S-CXL was two of the following three criteria: increase of “A” value, increase of “B” value, or decrease of minimum thickness evaluated with the ABCD progression display above 95% CI for the post-CXL population. RESULTS: Twenty-seven eyes of 22 patients were included. At a mean of 11 years of follow-up (maximum 13 years), S-CXL was able to maintain CDVA and induce significant regularization of the corneal surface as demonstrated by a significant decrease of the central keratoconus index (P =.035) and a decrease of anterior curvature (“A” value) starting from 2.54 ± 2.46, which reduced to 1.14 ± 1.60 (P =.005) at 10+ years of follow-up. Two of 27 eyes included showed significant progression after S-CXL (7.4%). CONCLUSIONS: S-CXL was confirmed to be a safe and effective treatment for progressive keratoconus with a failure rate of 7.4% at up to 13 years of follow-up. The authors suggest the use of a combined progression system that evaluates anterior and posterior curvature and with thickness map together with the knowledge of the noise level of the testing system.