Corneal light backscattering after transepithelial corneal crosslinking using iontophoresis in donor human corneal tissue

PURPOSE: To analyze the spatial distribution and time course of corneal light backscattering before and after transepithelial corneal crosslinking using iontophoresis. SETTING: Fondazione G.B. Bietti-IRCCS, Rome, Italy. DESIGN: Experimental study. METHODS: Three donor human eyes with an intact corneal epithelium had transepithelial iontophoresis corneal crosslinking (using rapid ultraviolet-A [UVA] irradiation), and 3 donor eyes without corneal epithelium had standard corneal crosslinking (using standard UVA irradiation). In addition, 3 donor eyes had iontophoresis and rapid corneal crosslinking after corneal deepithelialization (epi-off iontophoresis corneal crosslinking). Scheimpflug images (Pentacam HR) of each eye globe were acquired before and immediately after administration of riboflavin 0.1% solutions and 5, 10, 30, and 120 minutes after the corneal crosslinking procedures. Corneal light backscattering was quantified across the anterior 280 mu m thickness at several points from the optical center to 3.0 mm from the center. RESULTS: Light backscattering significantly increased after iontophoresis (P<.001) in specimens with and without intact epithelium. It decreased significantly after transepithelial iontophoresis corneal crosslinking and epi-off iontophoresis corneal crosslinking (P<.001), approaching the baseline values. After standard stromal soaking with riboflavin, a large increase in corneal light backscattering was found compared with baseline measurements (P<.001) that remained unchanged up to 30 minutes after standard corneal crosslinking (P=.92). The light backscattering increase after iontophoresis in corneas with epithelium was lower than after standard soaking (P=.01). No differences were found between specimens without epithelium after iontophoresis and standard stromal soaking (P=.06). CONCLUSIONS: Scheimpflug photography provided an indirect biomarker of stromal permeation of riboflavin. lontophoresis efficiently delivered riboflavin through the epithelium. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. (C) 2015 ASCRS and ESCRS