Rod-cone dysplasia in the collie.

Rod-cone dysplasia in the Collie was studied. Night blindness developed early (6 wk) and progressed to nearly total blindness by 1 year of age. Tapetal hyper-reflectivity, vessel attenuation, and optic nerve pallor were clinically evident by 6 months of age. Electroretinography demonstrated markedly reduced retinal response as early as 16 days of age. The results of selective breedings conformed to a single recessive pattern of inheritance.