Fig. 13 A peripheral retinal excavation results from loss of tissue from the inner layers as far external as the inner nuclear layer. The middle retinal layers show degeneration, and the outer layers are intact. (Hematoxylin eosin, original magnification ×250; Straatsma BR, Foos RY, Feman SS: Degenerative diseases of the peripheral retina. In Duane TD (ed): Clinical Ophthalmology, Vol 3. Hagerstown, MD: Harper Row, 1979:1–29)