The periodic acid Schiff reaction was applied to neurones in the Lateral Geniculate Body (L.G.B.) of a series of normal and blind patients over a wide age range. The quantity of the reaction product was determined as a measure of lipofuscin which was found to increase linearly with age in the L.G.B. neurones. The amount in the neurones of the blind patients was found to be less than that in the controls, and a further group of four patients with apparently normal vision and central nervous system disease had an intermediate amount of lipofuscin. It is suggested that the component of lipofuscin measured by this technique represents an index of both metabolic activity and functional activity of the neurone. The reduced amounts in the patients with C.N.S. disease may reflect reduced visual function in association with non-visual pathway disease.