Border Location Affects Local Progression Kinetics of Geographic Atrophy

Abstract

Purpose : To assess the impact of geographic atrophy (GA) location on GA local progression rate and the distribution of GA lesions.

Methods : We manually delineated GA on color fundus photographs of eyes with non-exudative age-related macular degeneration in the Age-Related Eye Disease Study. We included 2 visits that were 1 year apart for each eye with GA and then registered the images using vessel bifurcations. We calculated GA border expansion rate (BER) as the linear distance that GA border traveled over 1 year using a Euclidean distance map. Eye-specific BER was defined as the mean BER of all pixels (pixel size=10 μm) on GA border in each eye. We also determined GA prevalence and BER in 4 macular quadrants and at different distances from the foveal center.

Results : We included 237 eyes of 160 patients in the analysis. GA enlarged 1.51±1.96 mm² in area and 0.13±0.11 mm in distance over 1 year. GA area growth rate (mm²/year) was significantly associated with baseline GA area (P<0.001), number of lesions (P<0.001), and circularity index (P<0.001); in contrast, eye-specific BER (mm/year) was not significantly associated with any of these 3 morphological factors. The percentage of the retina affected by GA decreased from 49% to 1% as the retinal eccentricity increased from 0 to 4 mm (Figure A). By comparison, GA BER increased linearly as a function of retinal eccentricity (P<0.001), increasing from 0.07 mm/year at 0-0.5 mm from the foveal center to 0.18 mm/year at 3.5-4 mm from the foveal center (Figure B). The GA BER did not vary significantly across 4 macular quadrants (P=0.16), but the percentage of retina affected by GA was higher in the temporal than nasal quadrant (P=0.02), and was higher in the superior than inferior quadrant (P=0.01).

Conclusions : Measurements of eye-specific GA BER allows evaluation of GA progression without significant confounding effects from baseline GA area, shape, and lesion number. The local progression rate of GA increased as a function of distance from the foveal center within the macula, and was different from GA distribution. These findings suggest that the underlying mechanism responsible for GA initiation may be different from the mechanism of GA enlargement.

This is a 2021 ARVO Annual Meeting abstract.

 

A, The percentage of retina covered by GA decreased as the distance from the foveal center increased. B, In contrast, GA border expansion rate increased as a function of distance from the foveal center.