A randomised controlled trial on cross-linking protocols for the treatment of progressive keratoconus using isoosmolar and hypoosmolar riboflavin with the addition of sterile water in thin corneae.

Purpose: To present the outcomes of a randomised clinical trial for the treatment of progressive keratoconus using different kinds of riboflavin and the addition of sterile water in thin corneae.

Methods: A randomised study using epithelium-off corneal cross-linking (CXL) with continuous UVA irradiance 9 mW/cm² for 10 min (total fluence 5.4 J/cm²) and two kinds of riboflavin solutions: (i) isoosmolar dextran-based riboflavin (n = 27) and (ii) hypoosmolar dextran-free riboflavin (n = 27) for the treatment of progressive keratoconus. Visual acuity (corrected and uncorrected), tomographic parameters and endothelial cell count were obtained at baseline and after 1 year. Corneae thinner than 400 μm were also included. A safety limit of 400 μm was used, and sterile water was added if the corneae fell short of this limit during the treatment.

Primary outcome: Change in Kmax.

Results: There were no statistically significant differences in any of the parameters between the isoosmolar and hypoosmolar groups. In the isoosmolar group, 74% of the patients required the addition of sterile water, while only 15% required it in the hypoosmolar group. The measurements of densitometry in the 0-2 mm zone improved less in the group that received sterile water; otherwise, there were no statistically significant differences in any of the parameters between the groups that did and did not receive the addition of sterile water.

Conclusions: The results of this study demonstrate the efficacy and safety in using hypoosmolar riboflavin when performing CXL for progressive keratoconus. The results also demonstrate the efficacy and safety of using sterile water in corneae thinner than 400 μm.