Effect of corneal cross-linking on biomechanical properties of swollen rabbit corneas

Corneal cross-linking (CXL) is an effective method to prevent the progression of keratoconus. CXL combined with hypotonic riboflavin solution is a modified treatment for thin corneas, which are deemed to be below the safe thickness threshold. In this study, rabbit corneas were subjected to different hydration levels using different osmolarity of riboflavin dextran solutions before CXL. Inflation testing was performed to evaluate the corneal biomechanical stiffening effect of hypotonic riboflavin solutions crosslinking. One-month post-CXL, the stromal demarcation line depth (DLD) and the biomechanical property parameter - tangent modulus (Et) - were measured. All CXL groups showed higher Et than the corresponding Ctrl groups (all P < 0.001), however, the Et values showed no statistical differences between the CXL-ed groups with different hydration levels (all P > 0.05). The relative depth ratio of DLD to total corneal thickness (TCT) did not show significant differences (P > 0.05), while the DLD was statistically different in three CXL groups (P < 0.001). The research suggested that riboflavin solutions with different osmolarities are suitable for preoperative swelling of corneas with different thickness ranges. Furthermore, crosslinking with hypotonic riboflavin solutions has no significant effect on corneal biomechanical improvement under a certain degree of hydration.