Intraoperative corneal thickness change and clinical outcomes after corneal collagen crosslinking: Standard crosslinking versus hypotonic riboflavin

PURPOSE: To determine intraoperative changes in corneal thickness and outcomes of corneal collagen crosslinking (CXL) using 2 intraoperative regimens: riboflavin dextran or hypotonic riboflavin. SETTING: Cornea and refractive surgery practice, Teaneck, New Jersey, USA. DESIGN: Prospective randomized case series. METHODS: Eyes with keratoconus or corneal ectasia were treated. All eyes received preloading with riboflavin 0.1% in 20% dextran. During ultraviolet-A (UVA) exposure, patients were randomly assigned to 1 of 2 study arms; that is, riboflavin dextran or hypotonic riboflavin. lntraoperative pachymetry was measured before and after the corneal epithelium was removed, after initial riboflavin loading, and after UVA light exposure. Patients were evaluated for maximum keratometry (K), uncorrected distance visual acuity (UDVA), corrected distance visual acuity, corneal thickness, and endothelial cell count (ECC). RESULTS: Forty-eight eyes were treated. After removal of the epithelium and riboflavin loading, the mean pachymetry was 430 mu m and 432 mu m in the standard group and hypotonic group, respectively. Immediately after 30-minute UVA administration, the mean pachymetry was 302 mu m and 342 mu m, respectively. There was no statistically significant difference in the postoperative maximum K change, UDVA, corneal thickness, or ECC between the 2 groups. CONCLUSIONS: The cornea thinned substantially during the CXL procedure. The use of hypotonic riboflavin rather than riboflavin dextran during UVA administration decreased the amount of corneal thinning during the procedure by 30%, from 128 mu m to 90 mu m. However, there were no significant differences in clinical efficacy or changes in ECC or function between groups postoperatively. In general, corneal thinning during CXL did not seem to compromise the safety of the endothelium. (C) 2016 ASCRS and ESCRS