Retinal dysplasia and progressive atrophy in dogs irradiated during ocular development

Beagle dogs were given a single, whole-body gamma-radiation exposure at various stages during ocular development and were evaluated for the presence of ocular lesions. Dogs were exposed during middle or late pregnancy at 28 or 55 days postcoitus (dpc) or as neonates at 2 days postpartum (dpp). Mean whole-body and ocular doses ranged from 1.0 to 3.8 Gy. Dogs were sacrificed and ocular lesions were evaluated at 70 days, 2 years, or 4 years of age. Retinal dysplasias and atrophy were the most striking lesions related to radiation exposure. These lesions were bilateral and focal to diffuse in nature, and they increased in severity with increasing radiation dose. The stage of development at irradiation had a marked effect on the distribution of retinal lesions, with the most severe changes being present in that portion of the retina undergoing differentiation at the time of the insult. In dogs sacrificed at 70 days of age the lesions were primarily dysplasias consisting of ectopic nuclear aggregates in the photoreceptor layer, retinal folds, and retinal rosettes. With increasing age (up to 4 years), there appeared to be progression of the extent of the clinically evident lesions, and there was a change in the nature of the lesions from dysplasia to atrophy. This was accompanied by marked attenuation of the retinal vasculature.