OBJECTIVE: To characterize progression of geographic atrophy (GA) associated with age-related macular degeneration in AREDS as measured by digitized fundus photographs. METHODS: Fundus photographs from 181 of 4757 AREDS participants with a GA area of at least 0.5 disc areas at baseline or from participants who developed bilateral GA during follow-up were scanned, digitized, and evaluated longitudinally. Geographic atrophy area was determined using planimetry. Rates of progression from noncentral to central GA and of vision loss following development of central GA included the entire AREDS cohort. RESULTS: Median initial lesion size was 4.3 mm(2). Average change in digital area of GA from baseline was 2.03 mm(2) (standard error of the mean, 0.24 mm(2)) at 1 year, 3.78 mm(2) (0.24 mm(2)) at 2 years, 5.93 mm(2) (0.34 mm(2)) at 3 years, and 1.78 mm(2) (0.086 mm(2)) per year overall. Median time to developing central GA after any GA diagnosis was 2.5 years (95% confidence interval, 2.0-3.0). Average visual acuity decreased by 3.7 letters at first documentation of central GA, and by 22 letters at year 5. CONCLUSIONS: Growth of GA area can be reliably measured using standard fundus photographs that are digitized and subsequently graded at a reading center. Development of GA is associated with subsequent further growth of GA, development of central GA, and loss in central vision.