The ocular histopathologic and electron microscopic findings were determined in eyes obtained at autopsy from twins with dominant olivopontocerebellar atrophy (OPCA) and retinal degeneration (OPCA type III). On light microscopy, a retinal degeneration that involved primarily the photoreceptor layer was present and appeared to start in the macular area and spread to involve the peripheral fundus. The retinal pigment epithelium was variably hypopigmented and hyperpigmented. On electron microscopy, osmiophilic, multimembranous, and complex lipofuscin inclusions were present in conjunctival cells, keratocytes, lens epithelium, iris and ciliary body fibrocytes, occasional outer retinal cells, and retinal pigment epithelial cells. The twins' father and an older sister were also affected and had classic neurologic and ophthalmologic abnormalities. The similarities were noted between the clinical and ultrastructural findings between OPCA type III and the neuronal ceroid lipofuscinoses.