Heredofamilial retinal dystrophy in Guinea baboons. II. Electron microscopic observations.

Electron microscopic study of an inherited retinal degeneration in Guinea baboons disclosed primary pathologic alterations in photoreceptor cells. These changes were first seen in the perifoveal region. Cell death occurred in two forms: hydropic degeneration and densification and/or necrosis. The hydropic type was mainly associated with cone cells, whereas densification and/or necrosis was largely seen in rod cells. Lamellar bodies and granular membrane-bound inclusions were noted in the inner segments and soma. Mitochondria were vacuolated and formed membranous whorls. Bundles of filaments were arranged in parallel array in the soma synaptic endings. Clusters of tubules were present in the synaptic terminals. Preliminary biochemical studies on these animals have yielded no clues to the pathogenesis of the retinopathy.