The AngioVue provides a noninvasive OCT-based method for visualizing the vascular structures of the retina. It uses an 840-nm light source and has an A-scan rate of 70,000 scans/s and a bandwidth of 50 nm. Each volume contains 304 × 304 A-scans with two consecutive B-scans captured at each fixed position. Each volume scan is acquired in 3 seconds and consists of two orthogonal volumes that are used to minimize motion artifacts arising from microsaccades and fixation changes. The split-spectrum amplitude-decorrelation angiography (SSADA) method was used to capture the dynamic motion of the red blood cells and provide a high-resolution 3D visualization of perfused retinal vasculature.30 (link)The AngioVue characterizes vascular information at various user-defined retinal layers as a vessel density map and quantitatively as vessel density (%) (Fig. 1 ). Vessel density was automatically calculated as the proportion of measured area occupied by flowing blood vessels defined as pixels having decorrelation values acquired by the SSADA algorithm above the threshold level.
For this report, we analyzed vessel density in the peripapillary RNFL in images with a 4.5 × 4.5-mm field of view centered on the optic disc. Vessel density within the RNFL was measured from internal limiting membrane (ILM) to RNFL posterior boundary using standard AngioVue software (version 2015.1.0.90). Measurements were obtained in two areas. Whole enface image vessel density (wiVD) was measured in the entire 4.5 × 4.5-mm image, and circumpapillary vessel density (cpVD) was calculated in the region defined as a 750-μm-wide elliptical annulus extending from the optic disc boundary (Fig. 1 ).
Image quality review was completed on all scans according to a standard protocol established by the University of California, San Diego Imaging Data Evaluation and Analysis (IDEA) Reading Center. Trained graders reviewed scans and excluded poor quality images, defined as images with (1) a signal strength index of less than 48, (2) poor clarity, (3) residual motion artifacts visible as irregular vessel pattern or disc boundary on the enface angiogram, (4) local weak signal, or (5) RNFL segmentation errors. The location of the disc margin was reviewed for accuracy and adjusted manually if required.
For this report, we analyzed vessel density in the peripapillary RNFL in images with a 4.5 × 4.5-mm field of view centered on the optic disc. Vessel density within the RNFL was measured from internal limiting membrane (ILM) to RNFL posterior boundary using standard AngioVue software (version 2015.1.0.90). Measurements were obtained in two areas. Whole enface image vessel density (wiVD) was measured in the entire 4.5 × 4.5-mm image, and circumpapillary vessel density (cpVD) was calculated in the region defined as a 750-μm-wide elliptical annulus extending from the optic disc boundary (
Image quality review was completed on all scans according to a standard protocol established by the University of California, San Diego Imaging Data Evaluation and Analysis (IDEA) Reading Center. Trained graders reviewed scans and excluded poor quality images, defined as images with (1) a signal strength index of less than 48, (2) poor clarity, (3) residual motion artifacts visible as irregular vessel pattern or disc boundary on the enface angiogram, (4) local weak signal, or (5) RNFL segmentation errors. The location of the disc margin was reviewed for accuracy and adjusted manually if required.
