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Shelley Mo, Barbara Cortes, Toco Yuen Ping Chui, Richard B Rosen; Perfused Vessel Density of Peripapillary Capillaries vs. Major Vessels in Primary Open Angle Glaucoma (POAG) Using OCT Angiography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1647.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate peripapillary capillary perfused vessel density (PVD) in comparison to major vessel PVD in optical coherence tomography angiography (OCTA) images.
4.5x4.5mm optic disc OCTA scans of 10 healthy eyes and 27 eyes from patients with POAG were analyzed using custom software. Two OCTA layers were extracted from each scan: a slab extending from the vitreous to 50µm below the inner limiting membrane (ILM; superficial layer) and a layer extending from the ILM to the posterior boundary of the retinal nerve fiber layer (RNFL; RNFL layer). For each layer, two regions of interest (ROI) were defined: (1) an annulus with an inner diameter of 1.95mm and outer diameter of 3.45mm centered over the optic disc and (2) the entire image excluding a circle with a diameter of 1.95mm centered over the optic disc (Scripsema, IOVS 2016). Capillaries and major vessels were extracted using local and global thresholding, respectively. Capillary PVD was defined as the capillary area divided by the corresponding ROI area excluding the major vessel area. Major vessel PVD was defined as the major vessel area divided by the corresponding ROI area. Kruskal-Wallis tests and post-hoc Dunn tests with Holm correction were performed to assess statistical significance among disease stages for each parameter.
Consistent with a prior study, annulus and global capillary PVD decreased from control to severe POAG in the RNFL layer (Scripsema, IOVS 2016), with significant differences between control and mild POAG in global capillary PVD (15.9% difference, p<0.05). In the superficial layer, major vessel PVD increased from control to severe POAG in both the annulus and global ROI and capillary PVD decreased as in the RNFL layer. Major vessel PVD was not significantly different among groups in the RNFL layer. For all parameters, there were significant differences in the following comparisons: control vs. moderate, control vs. severe, and mild vs. severe (Fig 1).
Using a superficial slab on OCTA, PVD of capillaries and major vessels both appear to correlate with stage of disease. This type of image analysis may yield more information about the natural history of glaucomatous vascular changes and serve as a tool for diagnosing and staging POAG.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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