Accuracy and reliability of artery–vein differentiation in small-field macular OCT angiography

PurposeAccurate 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.ApproachSmall 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.ResultsA 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).ConclusionsAccurate 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.