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Amitha Domalpally, Ronald P Danis, Spencer Cleland, Liang Zhou, Ralph Trane, Yijun Huang, Barbara A Blodi; Measurement of Geographic Atrophy Using OCT Split Tool. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1291.
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© ARVO (1962-2015); The Authors (2016-present)
Geographic atrophy (GA), the end stage of dry age related macular degeneration, is a blinding eye disease with no available treatment. Regression in enlargement of GA area, typically measured using color photographs (FP), autofluorescence(FAF) and infrared imaging(IR) is used as an endpoint in clinical trials. Optical coherence tomography (OCT) is a widely available imaging method that can be used to measure GA. Due to the complexity in identifying margins of GA with OCT and manually intensive segmentation algorithms, OCT scans have been less used for GA measurements. The purpose of our study is to measure GA from OCT images using a novel software tool and compare the area of GA with other modalities.
GA area was assessed at baseline, 6 and 12 months using planimetry with FP, FAF and IR images. GA was measured using two separate criteria with OCT: 1. Contiguous retinal pigment epithelial layer (RPE) loss 2. Hyper-transmission through Bruch’s membrane (waterfall). Areas were measured using a custom developed “OCT split tool”, that allows evaluation of OCT B scans and registered infrared images simultaneously. Using this tool, the Ascan/Bscan coordinates of a region of interest, such as the lateral extent of RPE loss (orange cursors in the right image) or waterfall (yellow arrows) are identified. These coordinates can be annotated on the corresponding registered infra red image (left image) and connected to obtain an area measurement. All measurements were performed by 2 graders with adjudication by a senior grader.
OCT scans from 28 eyes with GA were evaluated. Of these, 3 eyes were excluded due to image quality. The mean baseline GA area and change in area with all modalities is listed in the table. There was no significant difference between the SDOCT measurements and area from other modalities at baseline. Mean difference between the two graders was 0.21 mm2 using RPE loss criteria and 0.36 mm2 using waterfall criteria.
The OCT split tool provides a reproducible method of assessing area of GA using SDOCT. The area of GA defined by RPE loss is smaller than that defined by waterfall, likely because hyper-transmission may occur in marginal areas of relatively intact RPE by OCT. Defining the hyper-transmission or “waterfall” zones as the borders of GA by OCT provides area measurements that are comparable to other modalities.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
OCT Split tool for measurement of GA
Area of GA
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