Abstract
PURPOSE: Accurate artery-vein (AV) differentiation in small-field macular optical coherence tomography angiography (OCTA) remains challenging due to a lack of standardized guidelines. We propose and validate criteria for 3 × 3 mm2 ( 10 deg × 10 deg on Spectralis; ∼ 2.9 × 2.9 mm2 ) macular scans. APPROACH: Small field-of-view (FOV) OCTA scans were analyzed using established AV criteria for large-field ( 12 × 12 mm2 ) OCTA, as applied by two masked readers and validated against color fundus photographs (CFPs) and near-infrared reflectance (NIR) images. Accuracy and reliability (Cohen's κ ) were assessed. Pixel-level AV masks were annotated with a standardized threshold. Vessel diameters and intensities were compared within our dataset and in the publicly available OCTA-500 dataset to assess whether intrinsic vessel features support AV differentiation. RESULTS: A total of 465 vessels from 20 healthy eyes were evaluated across 3 pseudo-branching orders using the criteria for OCTA. Annotators achieved high accuracy (95.1%, 92.3%) and strong intra/inter-rater reliability ( κ = 0.84 ) with similarly high AV classification accuracy within pseudo-third-order vessels (97.15%). No significant AV diameter differences were observed in either dataset ( p = 0.261 and 0.442). The mean intensity was similar in our dataset ( p = 0.277 ; |Δ| = 3.28 , 1.45% relative difference) but higher for veins in OCTA-500 ( p < 0.0001 ; |Δ| = 3.42 , 1.63% relative difference). CONCLUSIONS: Accurate and reproducible AV labeling is feasible in 3 × 3 mm2 scans, with strong inter- and intra-rater agreement. Vessel diameter and intensity add limited value. NIR-based alignment of OCTA with CFP provides reliable ground truth, supporting consistent manual labeling and OCTA segmentation.