Clinical-ultrastructural study of a retinal dystrophy.

An ultrastructural and cytochemical study was performed on the retina and retinal pigment epithelium of an eye surgically enucleated for choroidal melanoma from an otherwise healthy 31-year-old man. The patient and his identical twin show a retinal dystrophy that, based on clinical appearance, visual fields, amd electrophysiology, is most likely autosomal recessive retinitis pigmentosa. Rod and cone photoreceptors were reduced in numbers and outer segments were virtually absent in the region corresponding to the patient's poorest vision. In the region from approximately 20 degrees to 60 degrees (best field of vision), the outer segments of rods and cones were shortened and disorganized. The retinal pigment epithelium showed reactive changes in areas of most severe photoreceptor pathology, including re-duplication, loss of melanin, increased melanolysosomes, and migration of individual cells into the retina. The acid phosphatase reactivity of both the retinal pigment epithelium and photoreceptor cells appeared normal, as were the photoreceptor cilia and inner layers of the retina. This study thus provides improved ultrastructural documentation of a relatively early case of retinitis pigmentosa that may provide a foundation for further functional studies aimed at elucidation of this enigmatic retinal dystrophy.