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R. C. Caruso, W. M. Zein, D. Cunningham, W. S. Rasband; Quantitative Analysis of Fundus Autofluorescence Images Shows Short-Term Progression in Stargardt Disease. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6277.
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Autosomal recessive Stargardt disease/fundus flavimaculatus (STGD) is characterized by a gradual accumulation of lipofuscin flecks in the retinal pigment epithelium (RPE). This process leads to RPE and photoreceptor atrophy and results in visual loss. The purpose of this study was to explore disease progression in STGD in a relatively short (1 to 2 year) interval. To achieve this purpose, we analyzed fundus autofluorescence (AF) images to quantify both RPE atrophy and lipofuscin flecks.
Eighteen consecutive patients (15 women, 3 men, with a mean age of 42.1 years, and ranging in age from 24 to 68 years) have been included in this study to date. They all had fundus features and an inheritance pattern compatible with the diagnosis of STGD; they were screened for mutations in the ABCA4 gene. For each patient, two AF images were obtained with an average interval of 1.60 years apart. We used a Heidelberg Retinal Analyzer 2 to obtain 30 x 30 degree images, with 768 x 768 pixel resolution. Only patients in whom the atrophic lesion was entirely contained in the image were included. For each patient, only the data from one eye were analyzed. We quantified AF images using ImageJ software, and assessed statistical significance with paired-t tests.
1. Atrophic area. The macular area of severe hypofluorescence was used as an estimator of RPE atrophy. This area was automatically traced in thresholded images with optimized brightness and contrast. During the study interval, the atrophic area increased significantly from 4.46 +/- 2.65 square mm to 5.13 +/- 3.20 square mm (mean +/- standard deviation) (p = 0.01).2. Lipofuscin flecks. The summed area of hyperfluorescent particles was used as a quantifier of lipofuscin flecks. This area was automatically traced in thresholded images after bandpass filtering and normalization. During the study interval, the summed fleck area increased from 0.289 +/- 0.189 square mm to 0.376 +/- 0.280 square mm. This trend barely reached statistical significance (p = 0.05).
Progression in the severity of STGD could be documented in a 1 to 2 year interval, using AF as a quantitative estimator of this progression. This technique may be standardized as an outcome measure for clinical trials designed to arrest the progression of STGD. Given the rate of change of STGD with time, such a trial could be conducted in a relatively short follow-up interval. An equivalent approach may be applied to quantify hypofluorescent geographic atrophy and hyperfluorescent drusen in age-related macular disease.
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