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Paul Stetson, Zohar Yehoshua, Carlos Alexandre Garcia Filho, Giovanni Gregori, Philip Rosenfeld; OCT Minimum Intensity as a Predictor of Geographic Atrophy Enlargement. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6296.
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Changes in the minimum intensity (MI) of OCT A scans were previously shown to often represent abnormalities in the reflectivity and integrity of the outer nuclear layer and Henle fiber layer. MI was also shown to be significantly increased in areas of future growth at the margin of geographic atrophy (GA). The purpose of this study was to determine if MI can predict the exact locations of growth at the margin of GA and predict the rate of growth outside the margin as well.
Patients with GA measuring from 1.25 mm2 to 18mm2 were enrolled prospectively. OCT scans (Cirrus™ HD-OCT, Carl Zeiss Meditec Inc.) were analyzed at baseline and 52 weeks. Expert graders manually segmented OCT images of GA. For comparison to baseline, the 52-week follow-up scans were registered to the baseline scan coordinates using rigid transformation. MI values were studied within a margin of 180 microns around the boundary of GA. MI values in areas with progression of GA were compared using a one-sided t-test with MI values from areas that did not progress. ROC analysis was performed on MI values in the margin relative to lesion and background MI averages to determine sensitivity and specificity of prediction of growth. Average MI values in the margin were compared to overall growth rate to evaluate the prediction of growth outside the margin.
24 eyes were investigated, and no scans were excluded. A statistically significant elevation in MI (p<0.05) was seen in areas of growth in 22/24 cases (92%). Locations of growth in the margin at 52 weeks were predicted with 61% sensitivity and 61% specificity. MI values correlated significantly with overall growth rate, and high- and low-growth-rate subjects were identified with 80% sensitivity and 64% specificity.
These findings suggest that there is an increase in MI at the margins of GA prior to enlargement. Elevated MI may help predict areas of enlargement of GA, and may relate to overall rate of growth and be a useful screening tool for GA.
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