To evaluated the effect of oral administration of riboflavin combined with pulsed and continuous light accelerated scleral cross-linking on the histological and biomechanical properties of sclera in a guinea pig model to control the progression of myopia.

Thirty 4-week-old guinea pigs were divided into 5 groups, or the control group, non cross-linking group, conventional cross-linking group, pulse light cross-linking group and continuous light cross-linking group with 6 guinea pigs in each group.Three cross-linking groups were administered 0.1% riboflavin solution with vitamin C by gavage from 3 days before modeling to modeling process.The conventional cross-linking group underwent cross-linking with 1 hour of (ultraviolet A (UVA) exposure at 0.67 mW/cm², the pulse light cross-linking group received a pulsed-light accelerated crosslinking for 8 minuctes (1 second on/1 second off) of UVA exposure at 10 mW/cm², and the continuous light accelerated cross-linking group was crosslinked with continuous-light accelerated crosslinking at 10 mW/cm² for 4 minuctes.The same procedure was conducted on the non cross-linking group without UVA irradiation and 0.1% riboflavin solution before modeling and modeling process.No any intervene was carried out in the control group.Retinoscopy and the axial length measurement were performed before and after experiment.The animals were euthanized 2 weeks after experiment and then biomechanical and histopathological examinations of scleras were conducted.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.

Myopia models were established with an increased axial length and myopic diopter 2 weeks after myopic modeling process.Axial length in the non cross-linking group was longer than that of the control group at 2 weeks, with a siginificant difference between them (P<0.01). The myopic Diopter in the non cross-linking group was significantly increased in comprasion with the control group at 2 weeks (P<0.01). Compared with myopic eyes in the non cross-linking groups, axial length, diopter and strain assessment values were decreased significantly in three scleral cross-linking groups (all at P<0.01). The sclera ultimate load and stress assessment in the conventinal cross-lingking group, pulse light cross-linking group, continuous light cross-linking group were significantly higher than those in the non-cross-linking group Max stress: [2.20±0.03], [2.67±0.05], [2.41±0.04]Mpa vs.[1.30±0.02]Mpa; Max load: [1.92±0.03], [2.33±0.28], [1.91±0.03]P vs.[1.54±0.06]P) (all at P<0.01). Collagenous tissue of the scleras in the pulse light cross-linking group and continious ligh cross-linking group was similar in appearance to the control group.In addition, MMP2 expression of pulse light cross-linking group and continuous light cross-linking group was significantly increased, and TIMP-2 expression showed a reduce.

Pulsed and continuous light accelerated scleral cross-linking using oral administration of riboflavin and riboflavin UVA irradiation can effectively prevent the myopia development by increasing scleral biomechanical strength in guinea pig.

Riboflavin; Ultraviolet A; Scleral cross-linking; Myopia; Guinea