Radiotherapy-induced changes in vitreous humor

Vitreous humor (VH) is not considered as a critical structure in the radiotherapy process. In the present study, an experimental animal model was performed to examine the effects of radiotherapy on VH. The right eyes of twelve New Zealand rabbits were irradiated 60 Gy in 3 fractions, and the opposite (left) eyes were considered as control. Weekly ophthalmologic examination was performed after irradiation. At the end of the third month, enucleation and vitrectomy were conducted. The vitreous samples were subjected to metabolomic analyses, ELISA analyses, viscosity measurements, and electron microscopic examination. Two hundred seventy-five different metabolites were identified in control and experimental vitreous samples, and 34 were found to differ significantly between the groups. In multivariate analyses, a clear distinction was observed between control and irradiated vitreous samples. In the pathway analysis, affected pathways were mainly related to amino acid metabolism. A significant decrease was observed in type II, V, and XI collagens in the ELISA test. There was a non-significant decrease in type IX collagen. A non-significant decrease in viscosity was observed in experimental samples compared to control samples. Electron microscopy findings showed that the collagen fibrillar ultra-structure was disrupted, and there were collagen fragments dispersed in the experimental vitreous. An intact vitreous is essential for a healthy eye. In this study, it was observed that radiation caused changes on the vitreous that could have long-term consequences.