Effects of mitomycin C on the rat retina

To evaluate the retinal toxicity of mitomycin C injection in the rat eye, we conducted an electroretinographic study and a histopathologic study. Three different concentrations of mitomycin C (0.2, 0.3 and 0.4 mg/ml) were injected into either the vitreous cavity or the anterior chamber of the experimental eyes. A full-field electroretinogram was recorded before injection and 2, 4 and 7 days after injection. The retinas of all eyes were examined by light and electron microscopy. We found no evidence of electroretinographic and histologic changes 2 and 7 days after injection of 0.4 mg/ml of mitomycin C into the anterior chamber. However, profound electroretinographic changes did follow injection of the drug into the vitreous. These were absent with the 0.2-mg/ml solution at 7 days, mild with the 0.3-mg/ml solution at 7 days and profound with the 0.4-mg/ml solution as early as 2 days. Intravitreal injection of 0.4 mg/ml, however, showed selective degeneration of Müller cell process at day 2, retinal pigment epithelium changes at day 4 and irregular arrangement of the outer nuclear layer and photoreceptors at day 7. Intravitreal injection of mitomycin C in a concentration comparable to the one used clinically could cause retinal disorders, both functionally and histologically.