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 eyeswith an intact corneal epitheliumhad 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 280mmthickness at several points from the optical center to 3.0mmfrom 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 Z .92). The light backscattering increase after iontophoresis in corneas with epithelium was lower than after standard soaking (P Z .01). No differences were found between specimens without epithelium after iontophoresis and standard stromal soaking (P Z .06). CONCLUSIONS: Scheimpflug photography provided an indirect biomarker of stromal permeation of riboflavin. Iontophoresis efficiently delivered riboflavin through the epithelium.