A New Approach for the Segmentation of Three Distinct Retinal Capillary Plexuses Using Optical Coherence Tomography Angiography

PURPOSE: To segment three distinct retinal capillary plexuses by using optical coherence tomography angiography (OCTA). METHODS: This prospective study included 30 eyes of 15 healthy subjects. En face OCTA images generated by the AngioPlex platform were manually segmented by the “progressive matching” method to the superficial, middle, and deep capillary plexuses (SCP, MCP, and DCP, respectively). The estimated position of each plexus relative to the reference line was calculated. Vascular density (VD) and skeleton density (SD) analyses, as well as the interclass correlation coefficient and relative standard deviation, were performed on each capillary plexus. We also measured central retinal thickness (CRT) and ganglion cell layer thickness (GCT). RESULTS: Thirty eyes of 15 healthy subjects (9 females; average age of 28.33 ± 3.07 years) were included in the analysis. We defined the relative estimated positions of the outer boundary MCP to the RPEfit as MCP = 14.491 − 0.307 CRT − 1.443 GCT, while the outer boundary of DCP was 37.63 ± 7.04 μm below the IPL. The VDs of SCP, MCP, and DCP were 32.97% ± 3.90%, 45.05% ± 5.34%, and 37.34% ± 4.96%, respectively, while the SDs of SCP, MCP, and DCP were 14.45 ± 1.51 mm(−1), 19.80 ± 1.92 mm(−1), and 17.38 ± 1.97 mm(−1), respectively. CONCLUSIONS: With the progressive matching method, we segmented three capillary plexuses and defined the relative estimated positions of each capillary plexus to the reference line and calculated the VD and SD of three capillary plexuses in healthy subjects, providing controls for future studies. TRANSLATIONAL RELEVANCE: Our study provides a visual method for OCTA image vascular segmentation and provides reference and control for future studies on retinal three capillary plexuses.