Distinct Retinal Capillary Plexuses in Normal Eyes as Observed in Optical Coherence Tomography Angiography Axial Profile Analysis

Optical coherence tomography angiography (OCTA) allows the retinal microvasculature to be visualized at various retinal depths. Previous studies introduced OCTA axial profile analysis and showed regional variations in the number and location of axially distinct vascular retinal plexuses. OCTA acquisition and processing approaches, however, vary in terms of their resulting transverse and axial resolutions, and especially the latter could potentially influence the profile analysis results. Our study imaged normal eyes using the Spectralis OCT2 with a full-spectrum, probabilistic OCTA algorithm, that, in marked contrast to split-spectrum approaches, preserves the original high OCT axial resolution also within the resulting OCTA signal. En face OCTA images are generally created by averaging flow signals over a finite axial depth window. However, we assessed regional OCTA signal profiles at each depth position at full axial resolution. All regions had two sharp vessel density peaks near the inner and outer boundaries of the inner nuclear layer, indicating separate intermediate and deep capillary plexuses. The superficial vascular plexus (SVP) separated into two distinct peaks within the ganglion cell layer in the parafoveal zone. The nasal, superior, and inferior perifovea had a deeper SVP peak that was shifted anteriorly compared to the parafoveal zone. Axial vascular density analysis with high-resolution, full spectrum OCTA thus allows healthy retinal vasculature to be precisely reconstructed and may be useful for clinically assessing retinal pathology.