Corneal Resistance to Keratolysis After Collagen Crosslinking With Rose Bengal and Green Light

PURPOSE. The purpose of this study was to evaluate the resistance to degradation by collagenase A of corneas that have been crosslinked with Rose Bengal and green light (RGX). METHODS. The ex vivo crosslinking procedure was performed on enucleated rabbit corneas. Corneas were deepithelialized after applying 30% alcohol. Corneas were stained with Rose Bengal (RB, 0.1%) for 2 minutes and then exposed to green light (532 nm) at 0.25 W/cm(2) for times to deliver doses of 50, 100, 150, or 200 J/cm(2) (n = 5 per group). Five corneas were pretreated with riboflavin solution (0.1% riboflavin) for 15 minutes and irradiated with ultraviolet A (UVA) light (370 nm, 3 mW/cm(2)) for 30 minutes. Five corneas underwent only de-epithelialization and were otherwise untreated. Five corneas were stained with RB without light exposure. The central corneas of each group was removed with a 8.5-mm trephine and incubated at 378 degrees C in 0.3% collagenase A solution. Time to dissolution of each cornea was compared across treatments. RESULTS. Corneas treated with RGX were treated with light fluences of 50, 100, 150, and 200 J/cm(2); these corneas dissolved completely at 8.3 +/- 1.2, 11.1 +/- 1.4, 12.4 +/- 1.7, and 15.7 +/- 1.8 hours, respectively. Corneas treated by riboflavin and UVA light dissolved at 15.7 +/- 1.7 hours, and nontreated corneas dissolved at 6.1 +/- 1.3 hours. Corneas treated with only RB (no green light) dissolved at 9.3 +/- 1.7 hours. Compared with the untreated corneas, all of the RB groups and the riboflavin-UVA-treated group of corneas degraded statistically significantly slower than untreated corneas (P < 0.05). CONCLUSIONS. Crosslinking with RGX increased corneal resistance to digestion by collagenase comparable to that produced by riboflavin and UVA treatment.