Element analysis of the early stages of age-related macular degeneration

Abstract

The accumulation of basal laminar deposit (BLD) in the macula is considered to be a precursor of age-related macular degeneration. To learn more about the composition of BLD and the role of zinc in age-related macular degeneration, we investigated the elements in BLD, as well as in surrounding structures in 38 postmortem human maculae by electron-probe x-ray microanalysis. Basal laminar deposit and capillary vessel walls of the choriocapillaris appeared to contain no typical elements. Calcium, phosphorus, sulfur, zinc, and chlorine were detected in the lipofuscin granules in retinal pigment epithelium. Pigment granules of the retinal pigment epithelium and choroidal melanocytes contained predominantly sulfur and copper and, to a lesser degree, zinc, calcium, and iron. Local calcifications in Bruch's membrane were composed of large amounts of calcium and phosphorus and smaller amounts of zinc, iron, and chlorine. Metal-mirror fixation of the maculae, followed by freeze-drying and vapor fixation, showed additional amounts of sodium and potassium. From these experiments, no conclusions could be drawn about the origin of BLD. No relationship was found between the detection of zinc and the presence of BLD or drusen in the macula.