Progression of Geographic Atrophy as Measured by Digital Area; Results From the Age-Related Eye Disease Study (AREDS)

Abstract

Purpose:: To evaluate digital measurement of geographic atrophy (GA) area as an outcome for the study of age-related macular degeneration.

Methods:: 112 participants (140 eyes) with at least 0.5 disc areas of GA at the baseline visit of the Age-Related Eye Disease Study were evaluated. All available fundus photographs from the baseline visit and each follow-up visit were digitized and then graded for area of GA. Eleven participants with bilateral GA were graded independently by two reading centers and the results compared. Sixty-seven participants with at least 6 years of follow-up were stratified by quartile of baseline area of atrophy and median change in growth was calculated. Twenty-two participants included in this cohort had bilateral GA. The correlation between the eyes for change in area was calculated for this subset.

Results:: A comparison of the digital area grades from the two reading centers found high correlation (0.98 OD and 0.95 OS) between the centers with a mean difference in grades of 0.13 and 0.11 mm² OD and OS respectively. Linear growth of digital area over annual visits was observed in each of the first three quartiles with a potential ceiling effect observed for the 4^th quartile. For right eyes and left eyes combined, in the first quartile (median baseline: DA=0.66 and digital area=1.66 mm²) the change in digital area by 6 years was 3.14 mm²; for quartile 2 (median baseline: DA=1.17 and digital area=2.96 mm²) it was 9.67 mm²; for quartile 3 (median baseline: DA=2.25 and digital area=5.71 mm²) it was 11.96 mm²; and for quartile 4 (median baseline: DA=4.19 and digital area=10.67 mm²) it was 18.77 mm². The correlation between eyes of change in area in 22 participants with bilateral GA was 0.89 over all follow-up visits.

Conclusions:: Digital grading of geographic atrophy appears to be a reproducible method of evaluating morphologic progression. A strong correlation between eyes of change in area was observed for eyes presenting with bilateral disease.

Clinical Trial:: www.clinicaltrials.gov NCT00000145

Keywords: age-related macular degeneration • clinical (human) or epidemiologic studies: outcomes/complications • visual acuity