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Christian K. Brinkmann, Steffen Schmitz-Valckenberg, Arno P. Goebel, Monika Fleckenstein, Nina Stratmann, Frank G. Holz; Semi-automated Image Analysis Software For Quantification And Calculation Of Geographic Atrophy Progression. Invest. Ophthalmol. Vis. Sci. 2011;52(14):161.
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© ARVO (1962-2015); The Authors (2016-present)
To determine interobserver variability and reliability of longitudinal examinations of a novel semi-automated software for quantification of geographic atrophy (GA) progression due to age-related macular degeneration (AMD) based on fundus autofluorescence (FAF) imaging.
Three-field FAF (exc 488 nm, em 500-700 nm), near-infrared reflectance (NIR, 830 nm) and blue reflectance (BR, 488 nm) images (Heidelberg Retina Angiograph/Spectralis, Heidelberg Engineering, Germany) of 30 GA patients were recorded according to a standardized protocol at baseline, after 6 and 12 months. GA area was analyzed on central FAF images by seven independent readers at all visits using semi-automated software (RegionFinder, Heidelberg Engineering) and levels of agreement were assessed by Bland-Altman statistics.
The software allows a direct export of FAF images from the database, semi-automated detection of atrophic areas by selection of seeding points, shadow correction and vessel detection. Measurements are directly exported and graphically displayed in a grading report. Mean size of atrophy was 4.72 mm² (95%CI ± 1.21) at baseline, 5.37 mm² (95%CI ± 1.33) at 6 months and 5.91 mm² (95%CI ± 1.50) at 12 months. Mean difference of interobserver agreement ranged between -0.15 to 0.15 mm² (95%CI ± 0.08 to 0.16). Corresponding reflectance images were helpful for lesion boundary discrimination, particularly for evaluation of foveal GA involvement, in presence of poor image quality and for exclusion of fibrosis or regressed choroidal neovascularization. Measurement deviations may result from atrophy around the optic nerve head which is confluent with central atrophy, discrimination between drusen and GA-satellites, or from decreased foveal FAF signal due to either foveal atrophy or absorption from macular pigment.
The new image processing software offers an accurate, reproducible and time-efficient quantification of atrophy and progression rates. Major components of the software are automated according to FDA-requirements. The software tool facilitates measurements in natural history studies as well as monitoring of potential therapeutic effects in interventional trials of new agents aiming at slowing enlargement of geographic atrophy over time.
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