Intravitreal melatonin for the prevention of radiation retinopathy: a step beyond bevacizumab.

Purpose: Intravitreal bevacizumab has been utilized to mitigate radiation retinopathy, yet the potential role of intravitreal melatonin for its prevention remains unexplored. This study aims to evaluate and compare the efficacy of intravitreal melatonin and bevacizumab in preventing radiation retinopathy in an experimental animal model.

Materials and methods: Twelve healthy male New Zealand white rabbits (n = 24 eyes) received a single 3000 cGy irradiation dose in both eyes. Intravitreal melatonin (100 mcg/kg = 300 mcg/0.05 mL) was administered to the left eyes of six rabbits, and bevacizumab (1.25 mg/0.05 mL) to the left eyes of the remaining six, with sham injections given to the right eyes as controls. Six weeks after irradiation, bilateral enucleation was performed for biochemical and histopathological evaluation.

Results: Oxidative stress markers did not differ significantly between the groups (p = .827). Both melatonin and bevacizumab treatments markedly reduced axonal damage compared to the sham control group (p < .001). Melatonin also demonstrated a trend toward superior neuroprotective effects relative to bevacizumab, though this difference was not statistically significant (p = .07).

Conclusions: Intravitreal melatonin demonstrated efficacy comparable to bevacizumab in reducing radiation-induced retinopathy, with an encouraging trend toward enhanced neuroprotection. These findings position melatonin as a potential novel therapeutic for radiation retinopathy prophylaxis. Further research with larger, long-term studies is warranted to validate these results and investigate melatonin's broader applications in retinal protection.