Efficacy of Epithelium-Off and Epithelium-On Corneal Collagen Cross-Linking in Pediatric Keratoconus

Objectives: To evaluate the efficacy of riboflavin/ultraviolet A epithelium-off (epi-off) and epithelium-on (epi-on) corneal collagen cross-linking (CXL) in progressive pediatric keratoconus. Methods: Thirty-six eyes of 27 patients aged 18 years or younger (12–18 years) diagnosed with progressive keratoconus and treated with epi-off (n=18 eyes) or epi-on (n=18 eyes) CXL were included in this study. All patients were followed up for 24 months postoperatively. Results: At 24-month follow-up, the mean corrected distance visual acuity (CDVA) improved from 0.24±0.17 to 0.17±0.11 logMAR in the epi-off group (P=0.032). In the epi-on group, CDVA improved from 0.33±0.23 to 0.26±0.20 logMAR (P=0.012), but the improvement was not significantly different between groups (P>0.05). In the epi-off group, all mean K values improved: K1 (&Dgr;=−0.63 D, P=0.024), K2 (&Dgr;=−0.73 D, P=0.008), and Kmax (&Dgr;=−1.4 D, P=0.035), whereas in the epi-on group, Kmax and K2 did not change significantly and K1 (&Dgr;=0.68 D, P=0.029) significantly worsened. Postoperative mild corneal haze occurred in 5 eyes (28%) in the epi-off group. No postoperative complications were observed in the epi-on group. In 94.4% of the epi-off group, keratoconus regressed (44.4%) or stabilized (50.0%), whereas in the epi-on group, only 66.6% regressed (33.3%) or stabilized (33.3%), and the difference was significant (P=0.038). Conclusions: The efficacy of the epi-on procedure in terms of its ability to halt keratoconus progression appears to be 0.70 of the efficacy of epi-off CXL.