Comparison of central corneal thickness using ultrasound pachymetry during corneal collagen cross-linking

To study variation in central corneal thickness (CCT) during corneal collagen cross-linking(CXL) using ultrasound pachymetry.

Twenty patients (26 eyes) with progressing keratoconus undergoing riboflavin-UVA-induced CXL were involved in this study. Intraoperative CCT measurement using ultrasonic pachymetry was performed during the procedure. Measurements were obtained before operation, after epithelial removal, after riboflavin drop instillation, and after UVA irradiation.

Mean CCT was 495 +/- 56 and 450 +/- 52 microm before and after epithelial removal, respectively. Mean CCT was 443 +/- 42 and 411 +/- 39 microm after riboflavin drop instillation and after UVA irradiation, respectively. Statistically significant decreases in CCT occurred between the preoperative period and after epithelial removal, after riboflavin drop instillation and after UVA irradiation. Twenty-six eyes from 20 patients undergoing CXL were divided into 2 groups (I with CCT > or = 400 microm after UVA irradiation and II with CCT < 400 microm after UVA irradiation). No statistically significant difference was noted between I and II in preoperative endothelial cell count, but a statistically greater postoperative endothelial cell count was noted in I compared to II. A statistically significant difference was evident between preoperative and postoperative endothelial cell counts in Group II (P < 0.05).

Performing CXL with the use of riboflavin and UVA irradiation resulted in a statistically significant decrease in CCT, to a level where the corneal endothelium may be damaged.