Randomized Clinical Trial Comparing Customized Corneal Crosslinking: Epi-on in High Oxygen and Epi-off in Room Air for Keratoconus

Purpose: To compare clinical outcomes of customized transepithelial (epi-on) corneal crosslinking (CXL) in high oxygen and customized CXL with epithelial removal (epi-off) in room air for keratoconus (KC). Setting: Umeå University Hospital, Umeå, Sweden. Design: Prospective, randomized, single-masked, intraindividually comparing study. Methods: 32 participants with bilateral progressive KC were treated with bilateral customized topography-guided CXL, 30 mW/cm 2 ; 7.2 to 15 J/cm 2 and were randomized to epi-on in one eye (32 eyes) and epi-off in the fellow eye (32 eyes). Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), maximal keratometry (Kmax), subjective ocular discomfort, low-contrast visual acuities (LCVAs) at 10% and 2.5% contrast, ocular and anterior corneal wavefront aberrations, manifest refractive spherical equivalent, endothelial cell count (ECC), and adverse events were assessed through 24 months. Results: Both treatments showed improvements at 24 months in UDVA; −0.16 ± 0.24 ( P < .001) and −0.13 ± 0.20 logMAR ( P = .006), respectively, CDVA; −0.10 ± 0.11 ( P < .001) and −0.10 ± 0.12 ( P = .001), Kmax; −1.74 ± 1.31 ( P < .001) and −1.72 ± 1.36 D ( P < .001). LCVA 10% improved for both protocols ( P < .001), but LCVA 2.5% improved for epi-on CXL only ( P = .001). ECC was unaltered, and no adverse events occurred. The epi-on eyes had significantly less discomfort symptoms during the whole first week posttreatment ( P < .05). Conclusions: High-oxygen customized epi-on CXL is a viable alternative to room air customized epi-off CXL, with faster improvements in CDVA and LCVA and less early ocular discomfort.