for the GAP Study Group 3 PURPOSE. To determine the topographic distribution and progression of geographic atrophy (GA) in patients with AMD. METHODS. Fundus autofluorescence images (excitation 488, emission 500-700 nm) from 413 eyes of 413 subjects (median age, 77.0 years; inter quartile range [IQR], 72.0-82.0 years) of the Geographic Atrophy Progression (GAP) study were retrospectively analyzed. Using a modified Early Treatment Diabetic Retinopathy Study grid to divide the posterior pole into

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... nine different subfields plus periphery, the localization, size, and progression of atrophic patches were determined. Subfields, zones (center, inner and outer), and slices (nasal, temporal, inferior, superior) were compared using the Friedman test. RESULTS. The center and inner zones were involved in almost all eyes (>95%), while atrophy was less common in the outer zone subfields (76%). Inner zone atrophy size (median 4.00 mm 2 ) and progression rate (0.67 mm 2 /year) were significantly greater than in the outer zone (0.60 mm 2 and 0.42 mm 2 /year; P < 0.001). There was a trend toward outer zone subfield and periphery involvement with increasing total size of atrophy. In addition, the superior outer subfield was significantly more affected by atrophy as compared with the other three outer subfields of the grid (P < 0.001). CONCLUSIONS. Distribution and progression of existing GA patches depended both on the eccentricity from the center and total GA size. Central macular areas appeared most susceptible for the occurrence and expansion of GA. Refined analysis of distribution and directional spread is important to understand the natural history of the disease. This information will likely be helpful to design interventional GA clinical trials and associated anatomical outcome measures. (ClinicalTrials. gov number, NCT00599846.) (Invest Ophthalmol Vis Sci.