Comparison of geographic atrophy growth rates using different imaging modalities in the COMPLETE study

BACKGROUND AND OBJECTIVE: To compare the measurements and growth rates of geographic atrophy (GA) secondary to age-related macular degeneration (AMD) obtained using different imaging modalities. PATIENTS AND METHODS: Thirty patients with AMD and GA measuring from 1.25 mm² to 18 mm² based on spectral-domain optical coherence tomography (SD-OCT) fundus imaging were enrolled. Imaging was performed at baseline and at follow-up months 3, 6, 9, and 12, including autofluorescence (AF) imaging with a fundus camera-based flash system (TRC-50DX; Topcon Medical Systems, Oakland, NJ; AF excitation λ: 535-585 nm; detection λ: 605-715 nm), AF and fluorescein angiography (FA) imaging with a confocal scanning laser ophthalmoscopy (SLO) system (Spectralis; Heidelberg Engineering, Heidelberg, Germany; AF excitation λ: 488 nm; detection λ: > 500 nm), and SD-OCT en face imaging (Cirrus; Carl Zeiss Meditec, Dublin, CA). RESULTS: Average baseline square root measurements and enlargement rates of square root areas appeared similar across all modalities; 0.2 mm was the largest difference between any pair of measurement means. The intraclass correlation coefficients (ICC) were essentially equal to 1 for all comparisons of area measurements but were lower for growth rates than area measurements. Comparison of 26-week average enlargement rates showed no significant difference between the SLO AF image and enhanced SD-OCT en face image (mean difference: 0.01 mm; SD: 0.10; P = .70). CONCLUSION: Agreement among all imaging modalities in measuring the areas of GA at baseline diminished when the growth rates of GA were compared over 26 weeks, likely because each imaging technique identifies different anatomic features along the border of GA, which may appear similar but change at different rates.