Prophylactic effect of intravitreal melatonin and bevacizumab injection on radiotherapy-induced ocular complications

The aim of this study is to investigate the prophylactic effects of intravitreal melatonin and bevacizumab injections on radiation therapy (RT)-related ocular complications. Twelve male New Zealand white rabbits received 30 Gy RT to their bilateral ocular globes. Following RT, the left eyes of six rabbits were injected with intravitreal melatonin (100 mcg/kg), and the left eyes of the other six rabbits were injected with intravitreal bevacizumab (1.25 mg/mL), with the right eyes serving as the control group. After a six-week follow-up, bilateral enucleation was performed on all rabbits. The mean oxidative stress index values in the aspirated vitreous fluid were calculated as 22.3, 18.3, and 9.3 for the control, bevacizumab, and melatonin groups, respectively. Electron microscopy examinations revealed severe vascular and axonal structural damage in the retinal tissues of the control group. In the bevacizumab group, vascular damage was minimal, while axonal damage was moderate. In the melatonin group, no vascular damage was observed, and axonal damage was minimal. These results indicate that intravitreal melatonin injection is at least as effective as bevacizumab in the prophylaxis of radiation retinopathy and provides greater neuroprotective effects compared to bevacizumab.