Geographic Atrophy Growth is Strongly Related to Lesion Perimeter: Unifying Effects of Lesion Area, Number, and Circularity on Growth.

ABSTRACT: Purpose To investigate the underlying reason for the previously observed impact of baseline lesion size, lesion number, and circularity on geographic atrophy (GA) growth rate. Design Retrospective analysis of a multicenter, prospective, randomized controlled trial. Participants Age-Related Eye Disease Study (AREDS) participants with GA secondary to nonexudative age-related macular degeneration. Methods We manually delineated atrophic lesions on color fundus photographs of 318 eyes with GA followed over at least 2 visits (follow-up duration = 5.1 ± 3.0 years). We calculated GA area growth rate for each eye based on the first and last visit. GA perimeter-adjusted growth rate (mm/year) was defined as the ratio between GA area growth rate (mm 2 /year) and mean GA perimeter (mm) between the first and last visit for each eye. Main Outcome Measures GA area growth rate, growth rate of square root of GA area, and GA perimeter-adjusted growth rate. Results GA area growth rate was strongly correlated with mean GA perimeter (r2 = 0.66). GA area growth rate was associated with baseline GA area (r2 = 0.39, P Conclusion The growth rate of GA area is strongly associated with lesion perimeter. This relationship explains the previously observed influences of baseline GA size, lesion number, and circularity on GA growth rate. GA perimeter-adjusted growth rate is uncorrelated with the 3 morphological factors and may serve as a surrogate outcome measure to monitor GA progression in future studies.