Collagen Cross-Linking With Riboflavin in a Femtosecond Laser-Created Pocket in Rabbit Corneas: 6-Month Results

PURPOSE: To evaluate the initial changes of normal rabbit corneas after collagen cross-linking (CXL) with a femtosecond laser. DESIGN: Experimental study in animal eyes. METHODS: The right eyes of 10 male New Zealand white rabbits were treated with CXL with a femtosecond laser. A femtosecond laser was used to create an intrastromal pocket with 80-mu m depth and 7-mm diameter. Intrastromal administration of 0.1% riboflavin solution was made into the femtosecond laser created pocket and the cornea was irradiated with 3 mW/cm(2) ultraviolet A (UVA) light of mean 370 nm wavelength for 10 minutes. The corneal topography and pachymetry were evaluated by the Pentacam. All observations were performed preoperatively and at postoperative day 1, week 1, week 2, and months 1, 3, and 6. Light microscopy was applied to observe changes in the cornea at postoperative month 6. RESULTS: Cornea healing postoperatively was uneventful in all cases. The central corneal thickness (CCT) in the treated rabbit cornea reached the peak value at postoperative day 1, which descended gradually to the minimum at month 1 and returned to a high level at postoperative months 3 and 6. The CCT data postoperatively was significantly thicker than that preoperatively, except at postoperative month 1 (P > .05). Steepening of the operative area was found at the corneal front at postoperative day 1, which recovered dramatically after only 1 week. Then the treated area gradually flattened over the course of follow-up. In 8 of 10 rabbits, a demarcation line like change in the stroma was visible in the Scheimpflug image at slightly increased contrast as early as 1 month after CXL treatment. The micromorphologic examination also confirmed the existence of the demarcation line. Crystalline lens transparency remained unchanged all the time. CONCLUSIONS: CXL with a femtosecond laser appears to be safe. The cornea can realize a faster, uneventful recovery. The stromal demarcation line may be a direct clinical sign to detect an effective corneal cross-linking during the early phase postoperatively. (Am J Ophthalmol 2011; 152:22-27. (C) 2011 by Elsevier Inc. All rights reserved.)