Retinal degeneration in the macula of patients with Alzheimer's disease

Recent reports (Hinton et al. 1986; Blanks et al. 1989) document the involvement of the retina in the constellation of neurodegenerative changes present in Alzheimer's disease (AD). These studies demonstrate the degeneration of large numbers of optic nerve axons and loss of retinal ganglion cells (RGCs) in patients with AD, but the quantitative changes in the retina of patients with AD compared with age-matched controls have not been examined. An important question is whether the lesion affects the macula, the area of highest visual acuity and the region of the greatest density of cone photoreceptor cells and RGCs. Additionally, it is unknown if patients with AD have a uniform thinning of cells in the ganglion cell layer (GCL) or if there is a differential loss of the medium- to large-sized cells, as suggested earlier (Bassi et al. 1987) and documented histopathologically in some areas of the central nervous system of patients with AD (Kemper 1984). If patients with AD were to show a differential loss of large versus small RGCs with characteristic differences in density, distribution, central projections, and physiologic properties (see review by Rowe and Stone 1977), then a loss of the visual functions normally ascribed to these classes of mammalian RGCs might be expected. This quantitative study of the retinal lesions in the macula of patients with AD provides important data on the progression of the disease and may eventually be the basis for diagnostic procedures for assessing the severity of AD.