Randomized Controlled Trial Comparing Transepithelial Corneal Cross-linking Using Iontophoresis with the Dresden Protocol in Progressive Keratoconus

Abstract

To compare clinical outcomes of transepithelial corneal cross-linking using iontophoresis (T-ionto CL) and standard corneal cross-linking (standard CL) for the treatment of progressive keratoconus 12 months after the operation. Prospective randomized controlled clinical trial. Thirty-four eyes of 25 participants with progressive keratoconus were randomized into T-ionto CL (22 eyes) or standard CL (12 eyes). T-ionto CL was performed using an iontophoresis device with dextran-free 0.1% riboflavin-5-phosphate solution with enhancers and by irradiating the cornea with a 10 mW/cm2 ultraviolet A device for 9 minutes. Standard CL was performed according to the Dresden protocol. The primary outcome measure was stabilization of keratoconus after 12 months through analysis of maximum simulated keratometry readings (Kmax, diopters). Other outcome measures were corrected distance visual acuity (CDVA, logarithm of the minimum angle of resolution [logMAR]), manifest spherical equivalent refraction (D), central corneal thickness (CCT, micrometers) and endothelial cell density (ECD). Follow-up examinations were arranged at 3 and 7 days and 1, 3, 6, and 12 months. Twelve months after T-ionto CL and standard CL, Kmax on average flattened by-0.52±1.30 D (P=0.06) and-0.82±1.20 D (P= 0.04), respectively. The mean change in CDVA was-0.10±0.12 logMAR (P=0.003) and-0.03±0.06 logMAR (P= 0.10) after T-ionto CL and standard CL, respectively. The manifest spherical equivalent refraction changed on average by+0.71±1.44 D (P= 0.03) and+0.21±0.76 D (P= 0.38), respectively. The CCT and ECD measures did not change significantly in any group at 12 months. Significant differences in the outcome measures between treatments were found in the first week postoperatively. No complications occurred in the T-ionto CL group; 1 eye (8%) had sterile corneal infiltrates, which did not affect the final visual acuity, in the standard CL group. Significant visual and refractive improvements were found 12 months after T-ionto CL, though the average improvement in corneal topography readings was slightly lower than the Dresden protocol in the same period.