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Abstract
Repeated subcutaneous injections of urethan (ethyl carbamate) into newborn Long Evans rats resulted in degeneration of the photoreceptor and pigment epithelial cell retinal layers. Ophthalmoscopy and fluorescein angiography demonstrated early alterations in fundus pigmentation. In later stages these techniques revealed narrowed vessels, prominent retinal capillary beds, and leakage of fluorescein into the retina. Histologic examination of retinae showed early loss of visual receptor cells. Later changes included the presence of vascularized tufts of pigment epithelium extending into the retina and distortion of inner retinal layers. The presence of fenestrated vessels and degenerated capillaries within the disturbed pigment epithelium was visualized by electron microscopy. Hereditary factors were ruled out by breeding studies and appropriate controls. Similarities to other experimental retinopathies and to human pigmentary retinopathies are discussed