Sex-linked retinitis pigmentosa: ultrastructure of photoreceptors and pigment epithelium.

An ultrastructural study of a postmortem donor eye from a 24-year-old male patient with sex-linked retinitis pigmentosa showed abnormalities in all remaining cones and rods. Central foveal cones were reduced in number by about 50% and had shortened and severely distorted outer segments. Cones from the parafovea through the midperiphery gradually decreased in density and had no organized outer segments. In the far periphery, cones and rods had only slightly shortened outer segments. Photoreceptors equidistant from the fovea in all quadrants showed similar changes. The virtual absence of organized cone outer segments from the parafovea through the midperiphery was conspicuous in that this patient had full visual fields with large test lights 3 weeks prior to death. The pigment epithelium contained abnormally large numbers of melanolysosomes and few free melanin granules from the fovea through the midperiphery and few melanolysosomes and many free melanin granules in the far periphery. Whether or not these observations in the pigment epithelial cells represent a primary defect in this disease or reflect changes secondary to a defect in the photoreceptor cells remains to be defined.