Ultrastructure of the preretinal membrane in retinitis pigmentosa.

Light and electron microscopic examination of the retina and optic nerve in patients with retinitis pigmentosa has revealed a larger of fibrous astrocytes (preretinal membrane) apposed to the inner limiting lamina of the optic nerve retina. This preretinal membrane was centered on the disc, was many cell layers thick over the optic nerve and peripapillary retina, and was tapered to a single cell layer near its anterior margin. Processes of fibrous astrocytes from the optic nerve and peripapillary retina extend into the preretinal membrane through gaps in the inner limiting lamina of the optic nerve and peripapillary retina. The preretinal membrane may be responsible for the abnormally high fundus reflex, the waxy pallor of the disc, and posterior vitreous detachment frequently observed in patients with retinitis pigmentosa.