Retinal dysplasia of English springer spaniel dogs: light microscopy of the postnatal lesions.

The histologic features of retinal dysplasia were studied in 26 English springer spaniel dogs of one day to four years of age. Dysplastic lesions in neonatal pups occurred predominantly in the peripapillary tapetal area of sensory retina. They consisted of complex linear folds and rosettes which were composed of hyperplastic neuroblasts. Dysplasia usually was not associated with incomplete differentiation of the outer neuroblastic layer. The outer limiting membrane was absent locally and numerous patent subretinal capillaries existed in the region of folds. The dysplastic features may be related to aberrant development of Muller cells and of retinal capillaries. In adolescent dogs, dysplastic lesions were less complex and usually were not accompanied by aberrant capillaries. Focal or complete retinal separation was present in some adolescent dogs. In adult dogs, features of retinal atrophy were found within dysplastic areas. No significant histologic lesions were found in the extraocular tissues of 12 affected dogs which were surveyed extensively.