Figure 2
Measurements of optic nerve head vessel density (ONH-VD) and parapapillary choroidal vessel density (pCVD) and angular extent of choroidal microvasculature dropout (CMvD) in open-angle glaucoma (OAG) eye with CMvD using optical coherence tomography angiography (OCT-A). (Left) The red ellipse indicates the optic nerve head (ONH) margin, while the red lines denote the boundaries of ONH-VD measurement areas within the ONH. The sky blue outline indicates the Ī²-parapapillary atrophy (Ī²-PPA) margins, excluding large retinal vessels, identified on a scanning laser ophthalmoscopy (SLO) image, which are applied to same position within the Ī²-PPA on the OCT-A choroidal layer en-face image. (Middle) The region of interest (ROI) within the ONH, excluding large retinal vessels, were manually demarcated (yellow outline). These area of interest were used to measure the global ONH-VD using ImageJ software. Superotemporal and inferotemporal ONH area divided by horizontal line were used for superior and inferior ONH-VD measurement, respectively. (Right) The selected area of interest, excluding large retinal vessels, within the Ī²-PPA was converted to ROI, then applied to the 8- bit binary slab of OCT-A choroidal layer en-face image. The CMvD area is enclosed by the purple-colored border. The two points at which the circumferential border of the CMvD met the ONH margin were identified as the circumferential margins. The two yellow lines connect the ONH center to the circumferential margins of the CMvD. Angle Ī± is the angular extent (degrees) of the CMvD. All OCT-A images were created by Avanti system version 2018.1.0.37.
