Differentiating Veins From Arteries on Optical Coherence Tomography Angiography by Identifying Deep Capillary Plexus Vortices

PURPOSE: To introduce a simple method for differentiating retinal veins from arteries on optical coherence tomography angiography (OCTA). DESIGN: Cross-sectional pilot study. METHODS: Four default en face slabs including color depth encoded, grayscale full-thickness retina, superficial plexus, and deep capillary plexus (DCP) from nine 3 x 3-mm and nine 6 x 6-mm OCTA scans were exported and aligned. Nine ophthalmologists with minimum OCTA experience from 2 eye institutions were instructed to classify labeled vessels as arteries or veins in 3 stages. Classification was performed based on graders' own assessment at stage 1. Graders were taught that a capillary-free zone was an anatomic feature of arteries at stage 2 and were trained to identify veins originating from vortices within the DCP at stage 3. Grading accuracy was analyzed and correlated with grading time and graders' years in practice. RESULTS: Overall grading accuracy in stages 1, 2, and 3 was (50.4% +/- 17.0%), (75.4% +/- 6.0%), and (94.7% +/- 2.6%), respectively. Grading accuracy for 3x3-mm scans in stages 1, 2, and 3 was (49.9% +/- 16.3%), (79.2% +/- 9.6%), and (96.9% +/- 3.1%), respectively. Accuracy for 6 x6-mm scans in stages 1, 2, and 3 was (51.4% +/- 20.8%), (72.3% +/- 7.9%), and (93.2% +/- 3.3%), respectively. Grading performance improved significantly at each stage (all P < .001). No significant correlation was found between accuracy and time spent grading or between accuracy and years in practice (r = -0.164 to 0.617, all P >= .077). CONCLUSIONS: We describe a simple method for accurately distinguishing retinal arteries from veins on OCTA, which incorporates the use of vortices in the DCP to identify venous origin. (C) 2019 Elsevier Inc. All rights reserved.