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Malvika Arya, Vineela Varikuti, A. Yasin Alibhai, Chris Or, Caroline R Baumal, Andre J Witkin, Jay S Duker, Nadia K Waheed; Parafoveal Vessel Density Assessment by Optical Coherence Tomography Angiography (OCTA) in Diabetic Eyes. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2798. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Parafoveal vessel density (VD) varies on repetitive scanning by the same device and between different OCTA devices. This study was conducted to identify parameters for reliable intra-device repeatability and inter-device comparability of VD measurements in eyes with diabetic retinopathy (DR).
13 eyes of 8 patients were imaged three times consecutively on the Optovue RTVue XR Avanti (Optovue-SD), Zeiss Cirrus HD-OCT 5000 (Zeiss-SD), and Zeiss PLEX Elite 9000 (Zeiss-SS) OCTA devices. 6 eyes had non-proliferative DR and 7 had proliferative DR. En face 3x3mm foveal scans were analyzed by automated segmentation at superficial, deep, and full retinal layers. Zeiss-SD images were exported in two resolutions: 429x429 and 1024x1024. Images were binarized. Vessel Area Density (VAD) was calculated as area representing flow over total area. Binary images were skeletonized. Vessel Skeleton Density (VSD) was calculated as skeletonized area over total area (Fig 1). Coefficient of repeatability (CoR) was calculated to assess repeatability and comparability. A lower CoR value indicated higher reproducibility.
VAD measurements (Fig 2A) were not significantly different for Optovue-SD and Zeiss-SD devices. Zeiss-SS was significantly different from both spectral-domain devices (p<0.001). On VSD analysis, all devices were significantly different from each other (p<0.001), except for Zeiss-SS and Zeiss-SD 1024x1024. CoR values (Fig 2B) showed that VSD demonstrated greater intra-device reproducibility. Zeiss-SD 1024x1024 and Zeiss-SS showed greater repeatability.
In eyes with DR, VSD can reliably reproduce VD with repetitive scanning on the same device during follow-up visits. Conversely, VAD shows comparability across spectral-domain devices, irrespective of their resolution. Our findings are consistent with an earlier study in normal eyes, in which VAD showed greater inter-device comparability and VSD intra-device repeatability. The current study suggests that comparability between spectral-domain and swept-source OCTA devices may be reliably achieved by uniformizing resolution across different devices and subsequently computing VSD. This study will allow for VD assessment in varying severities of DR with dependable reproducibility.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure 1. Binarized and skeletonized images with VAD and VSD values
Figure 2. A: VAD and VSD values (%). B: Coefficient of Repeatability values (%)
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