Minimally Invasive Repetitive UVA Irradiation along with Riboflavin Treatment Increased the Strength of Sclera Collagen Cross-Linking

OBJECTIVE: This study aimed to investigate the efficacy of minimally invasive repetitive UVA irradiation along with riboflavin treatment on sclera collagen cross-linking in rabbits. METHOD: Forty-eight healthy adult New Zealand white rabbits were randomly divided into four groups: pseudosurgery group (group I), single-irradiation group (group II), duplicate-irradiation group (group III), and triplicate-irradiation group (group IV), with 12 rabbits in each group. For the single-irradiation group, a specially made LED light source was inserted through a minimally invasive conjunctival incision to gain close contact with the sclera for irradiation, and for the repetitive irradiation groups, the above experimental procedure was repeated once or twice every other week. Biomechanical parameters of the sclera including ultimate stress (σ) and 8% Young's modulus (E) were compared among the groups. RESULTS: In comparison with control group I, the ultimate stress of group II, group III, and group IV increased by 80.1%, 107.9%, and 182.1%, respectively, and their 8% Young's modulus increased by 106.1%, 159.5%, and 208.5%, respectively, one day after surgery (P < 0.01). CONCLUSION: Repetitive minimally invasive UVA irradiation with riboflavin significantly increased biomechanical strength of the sclera in the irradiated area, and biomechanical strength increased with repeated times of irradiation.