N-methyl-N-nitrosourea (NMU), a potent carcinogen in laboratory animals, has been shown to have a retinotoxic effect in Syrian hamsters. Six animals received two 5-mg doses of NMU intravenously at weekly intervals and six other animals received a single 5-mg dose. The retinal changes were fairly uniform and bilateral. The earliest lesion, observed at seven days consisted of arcades confined to the outer nuclear layer. The pigment epithelium revealed degenerative changes. Later there was widespread destruction of the rods and outer nuclear layer. The end stage consisted of a thin remnant of retina with an attenuated inner nuclear layer in direct contact with the choroid. There was intraretinal migration of pigment. The optic nerve and the anterior ocular structures including the lens showed no abnormality.
Herrold KM. Pigmentary Degeneration of the Retina Induced by N-Methyl-N-NitrosoureaAn Experimental Study in Syrian Hamsters. Arch Ophthalmol. 1967;78(5):650-653. doi:10.1001/archopht.1967.00980030652017