Objective: Age-related macular degeneration (AMD), the leading cause of blindness in people over age 65 in the United States, is a heterogeneous clinical entity in which retinal degeneration occurs predominantly in the macula in the context of aging and leads to impairment of central visual acuity (VA). AMD occurs in two general forms, one of which involves choroidal neovascularization (CNV) with subsequent formation of a disciform scar. This is often referred to as the neovascular or wet form. A second form, the subject of this study, is termed dry atrophic macular degeneration or otherwise geographic atrophy (GA) and involves a slow progressive atrophy of retinal pigment epithelial (RPE) cells and photoreceptors in the macula, also resulting in central vision loss. GA is estimated to affect up to one million people in the U.S. and there is no current treatment that can prevent its onset or retard its progression. While the etiology of GA is not completely understood, inflammatory processes involving the activation of resident immune cells of the retina called microglia are likely to contribute. The objective of this study is to study the progression of GA so as to be able to characterize in quantitative terms the natural progression of GA in patients not receiving any directed treatment; there is currently no approved treatment for GA.