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H. Smolen, G.-S. Ying, E. R. Martin, M. G. Maguire, The CAPT Research Group; Characteristics of Early Geographic Atrophy in the Complications of Age-Related Macular Degeneration Prevention Trial (CAPT). Invest. Ophthalmol. Vis. Sci. 2009;50(13):3915.
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To characterize incident geographic atrophy (GA) and to measure changes in its size, location and conformation as detected by annual stereoscopic color photographs and fluorescein angiograms (FAs).
Annual photographs and FAs were reviewed from an initial sample of 41 CAPT patients (bilateral large drusen at baseline) previously identified by the CAPT Reading Center as having developed GA in the untreated eye. 265 more eyes are currently in the grading process. Geographic atrophy was defined by the presence of either pigment change on color film or hyperfluorescence on FA and at least one other characteristic indicative of RPE involution such as marked concavity when viewed in stereo, visible choroidal vessels or sharp edges. No minimum size criterion was imposed. ImageJ software was used to measure the size and distance from the fovea of individual GA lesions on digitized color images. When photo quality was poor, FA was used to determine the borders of GA. 30 patients had ≥3 visits for assessing growth. Lesions were measured by a single grader after results from an inter-grader reliability study of 25 eyes yielded excellent results for both total and individual lesion area (intra-class correlation=0.992, both measures).
Among eyes with ≥2 years of follow-up for GA, the mean total GA area was 0.53mm2 at first detection, 0.87mm2 at 1 year and 1.29mm2 at 2 years. The mean individual lesion area was 0.27mm2 at detection, 0.35mm2 at 1 year, and 0.47mm2 at 2 years. GA initially presented as a single lesion in 23 (77%) of 30 eyes and as multiple lesions (2-8) in the remaining eyes. Over 2 years, 43% of patients maintained their baseline number of lesions, 27% developed additional lesions, and 27% had lesions merge. Among all lesions measured, the median size at initial presentation was 0.22mm2 (0.12 DA) and the average distance from the fovea was 0.74mm. The smallest lesion identified as GA with certainty was 0.05mm2.
With reference to FAs, incident GA lesions can be identified and reliably measured for the purpose of describing the natural history and growth of GA. This data will facilitate the design of future clinical trials evaluating therapies to halt the progression of GA.
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