Circular interleaving scan OCT enhances motion-contrast for 360 deg large-field iris angiography

In vivo imaging of human iris vasculature remains a persistent challenge, limiting our understanding of its relationship with ocular disease pathogenesis. Conventional raster scan optical coherence tomography angiography (OCTA) suffers from angular-dependent contrast (including blind spots), limited field of view, and prolonged imaging time—challenges that restrict its clinical utility. We introduce a circular interleaving scan OCTA method that overcomes these barriers by enabling 360 deg high-contrast iris angiography with consistent spatiotemporal sampling and optimized motion contrast. The circular scan design enables direction-optimized sampling: we configured circumferential sampling density to approximately twice the radial density, enhancing detection of radially oriented iris vasculature. A Cartesian–polar coordinate transformation was implemented for eye-motion compensation, vessel realignment, and vasculature reconstruction. Compared with raster scan OCTA, our circular scan protocol demonstrates 1.55× higher efficiency in iris vascular imaging, featuring a superior duty cycle (99.95% versus 82.00%) and eliminating redundant data acquisition from rectangular field corners (27.3% of the circular area). This method improves vessel density measurement by 39.0% and vessel count quantification by 25.2% relative to raster scans. By eliminating angular-dependent blind spots, our method significantly enhances vascular quantification reliability, paving the way to a better understanding of ocular diseases and holding promising potential for future clinical applications.