Intraoperative Corneal Thickness Measurements During Corneal Collagen Cross-Linking With Hypoosmolar Riboflavin Solution in Thin Corneas

Purpose: To monitor corneal thickness during the corneal collagen cross-linking procedure in corneal ectatic diseases, by using isoosmolar riboflavin solution with 20% dextran and hypoosmolar riboflavin solution without dextran. Methods: The corneal thickness measurements were obtained at 5 different time points: after epithelial removal, after isotonic riboflavin solution application for 30 minutes, after hypotonic riboflavin solution application for 10 minutes, and after 10 and 30 minutes of isotonic riboflavin solution application. Results: A total of 9 eyes of 9 patients with progressive keratoconus (n = 8) and pellucid marginal degeneration (n = 1) were included in this study. After epithelial debridement, the thinnest pachymetric readings were between 331 and 399 mu m (average, 376.11 +/- 19.88 mu m). The thinnest pachymetric measurements decreased significantly after the application of isoosmolar riboflavin solution for 30 minutes (by 55.22 +/- 13.40 mu m) and increased significantly after hypoosmolar riboflavin application for 10 minutes (by 59.56 +/- 29.71 mu m) (P < 0.01 for both). This artificial swelling effect was transient, and the thinnest pachymetric readings decreased significantly after 10 and 30 minutes of isoosmolar riboflavin application compared with thickness at the end of hypoosmolar riboflavin application (by 50.22 +/- 29.68 mu m and 65.11 +/- 27.94 mu m, respectively) (P < 0.01 for both). Conclusions: The iatrogenic swelling effect of the hypoosmolar riboflavin solution might be short acting and not durable throughout the UVA application in collagen cross-linking procedure.