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B. Chen, C. Tosha, M. B. Gorin, S. Nusinowitz; Measurement of Atrophic Lesion Size in Stargardt Disease (STGD) Using a Novel Methodology for Analysis of Autofluorescent (AF) Retinal Images. Invest. Ophthalmol. Vis. Sci. 2010;51(13):316.
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© ARVO (1962-2015); The Authors (2016-present)
1) To describe an automated edge-driven image segmentation algorithm to measure the area of atrophic lesions (AL) shown on AF imagery, and 2) to correlate panretinal function with AL area in STGD.
AF images were obtained with a confocal scanning laser ophthalmoscope. Image processing was accomplished automatically using Matlab, ImageJ, ImageMagick, and Edge-flow Image Segmentation linked together with LONI Pipeline. ALs were defined as areas with low intensities based on a two class Gaussian mixture model, and whose perimeter edge strengths were strong. Serial images were obtained from 24 STGD subjects (mean age = 49.12 ± 14.04 years) over a period of up to three years. Structure-function relationships were evaluated with electroretinography (ERG).
The mean variation of AL area measurements across a series of AF images collected on the same day with different acquisition settings was 1.1% ± 0.3% (range = 0.6% - 2.8%), suggesting a highly reliable methodology. The average size of the AL(s) in STGD patients at baseline was 22.4 (± 28.7) mm2. AL area was not correlated with age or the underlying ABCA variant. The median growth of the AL over 1.0, 2.0, and 3.0 years was 7.7%, 16.2% and 20.9%, respectively. The rate of change of the AL was uncorrelated with age but was correlated with lesion size at baseline; AL 20 mm2). Rod- and cone- mediated ERG amplitudes were correlated with the total area of the AL; the larger the AL, the poorer the ERG response, with a greater impact of lesion size on the cone responses.
A highly reliable, sensitive and automated algorithm for measuring the size of ALs is described. Progression of AL area greater than 2.0% can be considered to represent meaningful change not attributable to normal variation in image processing parameters. This methodology offers a highly sensitive means of monitoring progressive change in retinal structure in patients with well-defined ALs that will be useful in clinical trials to quantify phenotypic changes in response to therapy.
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