Softening of drusen and subretinal neovascularization.

On the basis of clinico-pathological examination, drusen were divided into hard and soft. A few small, hard drusen with a hyaline composition were found in 50 per cent of the normal aged eyes examined. The appearance of drusen of softer consistency often heralded the onset of senile macular degeneration. Soft drusen resulted either from the breakdown of the hyaline content of hard drusen or from the focal aggregation into mounds of membranous debris which accumulated as a widespread shallow layer between the basement membrane of the pigment epithelium and Bruch's membrane. Softening of drusen was most evident when the retinal pigment epithelium demonstrated the greatest proliferative activity, with migration of cells into the retina and the formation of the basal laminar deposit. It was at this stage that subretinal neovascularization was first detected. A patient in whom the gradual development of small soft drusen and an associated pigmentary disturbance was followed by subretinal new vessel formation is reported. The eye was subsequently found to have five separate breaks in Bruch's membrane and the ultrastructural findings are described.