To compare intraoperative changes in central corneal thickness (CCT) during corneal cross-linking, using 2 different isotonic riboflavin solutions either with dextran or with hydroxy propyl methylcellulose, in the treatment of progressive keratoconus.
In this retrospective study, we analyzed records of corneal thickness measurements, taken during various steps of cross-linking. Cross-linking was performed using either isotonic riboflavin with dextran (group A) or isotonic riboflavin with hydroxy propyl methylcellulose (without dextran) (group B). CCT measurements were recorded before and after epithelial removal, after saturation with respective isotonic riboflavin solution, after use of hypotonic riboflavin in selected cases, and after ultraviolet A (UV-A) application. A mixed-way analysis of variance was conducted on CCT readings within each group and between both groups, and p < 0.05 was considered significant.
In group A (100 cases), after saturation with isotonic riboflavin, CCT was decreased by a mean of 51.4 μm (12.1%). In 64%, CCT was <400 μm and additional hypotonic riboflavin was used. After UV-A irradiation, CCT was decreased by a mean of 46.7 μm (11.4%). In group B (100 cases), after saturation with isotonic riboflavin, CCT was increased by a mean of 109.4 μm (26.1%). After UV-A exposure, CCT was increased by a mean of 59.2 μm (11.2%). There was a substantial main effect for time on CCT during corneal cross-linking (CXL), p < 0.001, within both groups. The main effect comparing CCT readings between groups A and B was also significant, p < 0.001.
During cross-linking, isotonic riboflavin with dextran causes a significant decrease in corneal thickness, whereas dextran-free isotonic riboflavin causes a significant increase in corneal thickness, thus facilitating the procedure.