Purpose  To evaluate the feasibility of UVA-riboflavin cross-linking method on sclera thinning disorders by investigating the dynamic changes of electroretinogram(ERG), histological appearance and apoptosis of the rabbit eyeball after scleral cross-linking.
Methods  Forty New Zealand White rabbits was randomly divided into four groups, 10 in the control group(Group A) and 10 in every cross-linking groups(Group B, C, D). After general and local anesthesia, only the right eye of each rabbit was treated. The conjunctiva was incised, and the equatorial sclera of the upper nasal quadrant was exposed. 0.1% riboflavin-5-phosphate saline solution was dropped onto the equatorial sclera 5 min before the irradiation and every 5 min during the irradiation. UVA irradiation(370 nm, 3mw/cm², 30min, 5.4 J/cm²) was applied in the cross-linking groups(Group B, C and D) respectively at 0.5cm, 1.0cm and 1.5cm distance. UVA irradiation was not applied in Group A. Then, the animals were randomly divided into 2 subsets depending on the postoperative time interval of either 1 week or 1 month, respectively: 1. At one week after surgery, ERG measurements of the right rabbits eyes was performed for twenty rabbits(5 in every group). Then, these rabbits were sacrificed, and the treated scleral specimens were stained with haematoxylin and eosin. In addition, the Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling(TUNEL) was used for the detection of apoptosis. 2. At one month after surgery, twenty rabbits(5 in every group) were killed and performed the histological and TUNEL assay in the same way. The parameters amplitude(μV) and latency(ms) of the waves in ERG at 1 week and 1 month were analysed, and the sections of HE and TUNEL were compared.
Results  1. One week and one month after cross-linking, the amplitude level of P-waves in 30Hz Flicker ERG was decreased in Group B(irradiation at 0.5cm distance) than in Group A(the control group) (p﹤0.05). There was no difference in Group A, C and D. 2. At one week and one month after surgery, there was considerable scleral edema in the treatment area. The choroid and retina in all groups were intact. 3. At one week and one month after surgery, TUNEL-positive cell were identified in the adjacent inner nuclear layer and sclera in Group B. But there was no considerable difference in other groups.
Conclusion  Scleral UVA-riboflavin Cross-linking is safe for rabbit’s retinal function and ocular histopathologic appearance, when the UVA(370nm, 3mw/cm², 30min) irradiation distance is set 1.0cm.