A comparative study between epithelium-on and epithelium-off collagen cross-linking with riboflavin and ultraviolet radiation in the treatment of early keratoconus

Purpose We aimed to carry out a comparative study between epithelium-on and epithelium-off collagen cross-linking (CXL) in the treatment of early keratoconus.Patients and methods The present study was a prospective, randomized study. We included 40 eyes from 25 patients, with a mean age of 24 years (range: 15–35 years). There were 15 males and 10 females, and all of them underwent corneal CXL using riboflavin and ultraviolet-A light at the Tipa Eye Hospital, Assuit.Results Among the samples included, 20 eyes underwent epithelium-on corneal collagen CXL, and 20 eyes underwent epithelium-off corneal CXL. The incidence of postoperative pain was lowered by about 20% in the transepithelial group as compared with the epithelial-off group in the first postoperative week. In addition, the incidence of postoperative corneal haze was lowered by about 50% in the transepithelial group as compared with the epithelial-off group in the first postoperative week. It was found that in the transepithelial CXL technique the formation of CXL appeared to take place in the upper-third of the corneal stroma, 20–30 μm beneath bowman membrane. With the classic debridement technique, CXL formed much deeper in the stoma in group I. Statistically nonsignificant corneal thinning was recorded after 3 and 6 months. In group II, statistically nonsignificant corneal thinning was recorded after 3 months, but after 6 months there was some sort of regression in the form of corneal thinning by about 5–10 μm in 20% of cases.Conclusion We found that the epithelium-off CXL and the epithelium-on CXL were effective in stabilizing the progression of keratoconus at least for 6 months; however, the epithelium-off CXL appeared to be much more effective in improving the refractive best-corrected visual acuity and topographic outcomes in keratoconic eyes compared with the epithelium-on CXL