Comparison of epithelium-off and transepithelial corneal collagen cross-linking for treatment of keratoconus

PurposeThe aim of the study was to assess the safety and efficacy of epithelium-off corneal cross-linking (conventional cross-linking) versus epithelium-on cross-linking (epithelium-on cross-linking) in the treatment of keratoconus.Patients and MethodsThis study was a nonrandomized comparative trial. Forty-three eyes of 35 patients were included in this study. All eyes were subjected to the preoperative and postoperative measures including uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA), pachymetry, simulated keratometry, and corneal topography. The preoperative and postoperative data were analyzed at baseline and at 3, 6, and 12 months in all eyes. The epithelium-off cross-linking group (the CXL group) included 25 eyes of 20 patients, whereas the epithelium-on cross-linking group (the transepithelial CXL group) included 18 eyes of 15 patients. The thinnest corneal thickness was at least 400 μm in all eyes.ResultsIn the epithelium-off CXL group, there was a remarkable improvement regarding postoperative UCVA and BCVA (one line or more). Average K showed a marked reduction reaching more than 2 diopters. The mean astigmatism showed unremarkable changes. The main central corneal thickness showed very marked corneal thinning with reduction in the corneal thickness reaching more than 50 um in many cases. In the epithelium-on CXL group, there was unremarkable improvement regarding postoperative UCVA and BCVA. Average K showed almost no changes during the 12-month follow-up period. The mean astigmatism showed minimal changes. In addition, the main central corneal thickness showed considerable corneal thinning with reduction in the corneal thickness reaching up to 30 μm.ConclusionThis study has proved that epithelium-on CXL is superior to epithelium-off CXL regarding pain, complications, and early patient convalescence. However, epithelium-off CXL is superior to epithelium-on CXL regarding the efficacy in visual stabilization and improvement. In short, this study concluded that conventional epithelium-off CXL is better than epithelium-on CXL.