Interest in fundus autofluorescence (FAF) imaging in the setting of geographic atrophy (GA) secondary to nonneovascular age-related macular degeneration (AMD) has recently increased. Attempts have been made to describe FAF phenotypes1–3 and to correlate these phenotypes with prognosis for disease progression.3–6 Several studies have also investigated the natural progression of GA and have primarily used either color fundus photographs (CFP)7–10 or FAF images.5,6,11,12 The Age-Related Eye Disease Study Research Group9,10 and the natural history studies of GA performed by Sunness et al7,8 used different techniques of measuring GA with color fundus photos. Both these groups used film instead of digital images and required special procedures to calculate GA area. Although these techniques were shown to be relatively reliable, they were arguably labor intensive and involved using either standardized grids over photographic slides9 or projections of film onto paper, repeated manual tracings, and corrections for multiple magnifications.7,8 More recently, the Age-Related Eye Disease Study Research Group reported growth rates of GA using digitized standard CFP.10 Furthermore, these methods required adjustments based on the Macular Photocoagulation Study standard disk size (1 disk area [DA] defined as 2.54 mm2)7 or other standard disk sizes (e.g., 2.66 mm2),10 and the resulting measurements were approximations. Other researchers have recently described the use of digital FAF images for measuring GA and predicting progression.5,6,11,12 The recent emergence of clinical trials to evaluate new therapies for nonneovascular AMD has increased the need for reliable, accurate, and simple means of monitoring GA size and progression. Whether CFP or FAF is superior for measuring GA area is not known. In this study, we compared digital CFP and FAF in the setting of GA secondary to nonneovascular AMD. We sought to determine whether CFP or FAF has less grader variability in the measurement of total GA area at a given time point.
