Riboflavin/ultraviolet A-induced collagen cross-linking in rabbit corneal scar.

Aim: To evaluate the biomechanical stability of the corneal scar treating with riboflavin and ultraviolet A (UVA).

Methods: Totally 86 New Zeal rabbits were divided into control group (group A, =8) and trauma groups [group B (=27), group C (=24) and group D (=27)]. Then groups B, C and D were divided into three sub-groups according to the time points of sacrifice, groups Ba, Ca and Da (4wk, =8); Bb, Cb and Db (6wk, =8); Bc (=11), Cc (=8) and Dc (8wk, =11). The right corneas of these 78 rabbits in the trauma groups were penetrated. Group B were only sutured. Group C were treated with corneal cross-linking (CXL) immediately after suturing. Group D were treated with CXL seven days after suturing. The corneal scar strips of 4.0×10.0 mm were cut and the stress and Young's modulus at 10% strain were evaluated. Samples from the three rabbits of group Bc and three of group Dc were used to measure the expression of alpha smooth muscle action (α-SMA).

Results: The mechanical strength of the corneal scar increased with time, and was strongest at 8wk after the injury. The ultimate stress of corneal scar (group D) were 2.17±0.52 MPa, 2.92±0.63 MPa, and 4.21±0.68 Mpa at 4wk, 6wk and 8wk, respectively; Young's modulus were 10.94±1.57 MPa, 11.16±2.50 MPa, and 13.36±2.10 Mpa, which were higher than that of other groups except for normal control. The expression of α-SMA in group B and group D were 0.28±0.11 and 0.65±0.20, respectively, and the difference was statistically significant (=0.048).

Conclusion: CXL with riboflavin/UVA at seven days after suturing improved the biomechanical properties of corneal scars most effectively in the present study.