Relationship of Topographic Distribution of Geographic Atrophy to Visual Acuity in Nonexudative Age-Related Macular Degeneration

Abstract

To investigate the topographic distribution of geographic atrophy (GA) and to identify an anatomic endpoint that correlates with visual acuity (VA) in eyes with GA. Retrospective analysis of a multicenter, prospective, randomized controlled trial. The Age-Related Eye Disease Study participants with GA secondary to nonexudative age-related macular degeneration. We manually delineated GA on 1654 fundus photographs of 365 eyes. We measured GA areas in 9 subfields on the Early Treatment Diabetic Retinopathy Study (ETDRS) grid and correlated them with VA via a mixed-effects model. We determined the optimal diameter for the central zone by varying the diameter from 0 to 10 mm until the highest r2 between GA area in the central zone and VA was achieved. We estimated the VA decline rate over 8 years using a linear mixed model. Geographic atrophy area in macular subfields and VA. The percentage of area affected by GA declined as a function of retinal eccentricity. GA area was higher in the temporal than the nasal region (1.30 ± 1.75 mm2 vs. 1.10 ± 1.62 mm2; P= 0.005) and in the superior than the inferior region (1.26 ± 1.73 mm2 vs. 1.03 ± 1.53 mm2; P < 0.001). Total GA area correlated poorly with VA (r2= 0.07). Among GA areas in 9 subfields, only GA area in the central zone was associated independently with VA (P < 0.001). We determined 1 mm as the optimal diameter for the central zone in which GA area correlated best with VA (r2= 0.45). On average, full GA coverage of the central 1-mm diameter zone corresponded to 34.8 letters' decline in VA. The VA decline rate was comparable between eyes with initial noncentral and central GA before GA covered the entire central 1-mm diameter zone (2.7 letters/year vs. 2.8 letters/year; P= 0.94). The prevalence of GA varies significantly across different macular regions. Although total GA area was associated poorly with VA, GA area in the central 1-mm diameter zone was correlated significantly with VA and may serve as a surrogate endpoint in clinical trials.