Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

Precis: When comparing 4.5x4.5 mm to 6.0x6.0 mm optical coherence tomography angiography scans of the radial peripapillary capillaries (RPCs) for glaucoma diagnostic capability, there was a trend of 4.5 scans outperforming 6.0 scans, especially for inferior, nasal, and superior quadrants. Objectives: The main purpose of this study was to compare diagnostic ability of peripapillary vessel parameters from 4.5x4.5 mm (4.5) and 6.0x6.0 mm (6.0) spectral-domain optical coherence tomography angiography scans of the RPC in detecting primary open-angle glaucoma from nonglaucoma eyes. Methods: Consecutive patients from an academic glaucoma clinic underwent 4.5 and 6.0 scans (CIRRUS HD-OCT 5000 with AngioPlex OCT Angiography; ZEISS, Dublin, CA). Automatic segmentation created en face RPC images. Vessel area density, vessel skeleton density, and flux were calculated using custom quantification software, and perfusion density and flux index (FI) using automated quantification software. Area under the curve statistics included age and hypertension in the analysis. Results: Of 173 eyes from 123 patients who underwent both 4.5 and 6.0 imaging, 32 primary open-angle glaucoma eyes from 32 patients and 95 nonglaucoma eyes from 95 patients were studied. For the global region of 4.5 versus 6.0 scans, area under the curve was 0.940 and 0.916 for vessel area density (P=0.286); 0.941 and 0.921 for vessel skeleton density (P=0.385); 0.942 and 0.916 for flux (P=0.239); 0.912 and 0.884 for perfusion density (P=0.103); and 0.913 and 0.865 for FI (P=0.159), respectively. For the quadrant regions, 4.5 images significantly outperformed 6.0 images for the superior and inferior quadrants for flux and superior and nasal quadrants for FI (P-values=0.007, 0.047, 0.011, 0.007, respectively); other quadrant differences were not significant. Conclusions: Parameters from 4.5 scans generally outperformed those from 6.0 scans in the global and quadrant regions, suggesting greater digital resolution in 4.5 scans of the immediate peripapillary RPC is important in detecting glaucomatous changes.