Macrophages related to Bruch's membrane in age-related macular degeneration.

This report describes focal thinning of Bruch's membrane in age-related macular degeneration and suggests a role for macrophages in this process. Electron microscopy was performed on four eyes ranging from normal ageing to age-related macular degeneration with early subretinal neovascularisation. As degeneration progressed multiple segments of thinning of Bruch's membrane were observed and macrophages appeared to engulf fragments of the outer collagenous zone. An associated finding at this stage was the shedding of membranous debris by the retinal pigment epithelium and its deposition within Bruch's membrane. This debris forms the basis of soft drusen but in the presence of this material thinning of Bruch's membrane was also observed beneath hard drusen. It is suggested that the widespread accumulation of phospholipid-containing membranes together with the focal concentration of lipid in hard drusen attract macrophages.