3D analysis of age-related compensation of retinal capillary plexuses in normal population via wide-field volume-mode SS-OCTA: Focus on interlayer connecting branches

PURPOSE: To explore the age-related compensatory features of retinal capillary plexuses (RCP) in normal people, with emphasis on the role of interlayer connecting branches. METHODS: Wide-field volume-mode swept-source optical coherence tomography angiography (SS-OCTA) B-scans of 3 × 3 mm and 12×12 mm of 60 healthy eyes were collected. Pearson correlation analyzed blood flow indices including blood volume (BV), vessel surface area (VSA), and vessel density (VD); 3D volume rendering observed interlayer connecting branches. RESULTS: 1. Blood flow compensation: 3 × 3 mm macular BV and VSA showed no correlation with age; BV and VSA in the 12×12 mm area decreased with age. Only the macular VD of the intermediate capillary plexus (ICP) dropped significantly, with a correlation coefficient twice that of the superficial vascular plexus (SVP) and deep capillary plexus (DCP). 2. Interlayer branches: Three types were identified: small, vertical ones (prevalent in young people) and two types of large, oblique ones (prominent in the elderly). With age, total branch number decreased, more markedly in vertical ones; oblique ones became dominant, accompanied by reduced small vessels (most marked in ICP) and thickened large vessels (most prominent in DCP). CONCLUSION: Normal RCP has an age-related compensatory mechanism: "sacrificing peripheral blood flow to protect macular blood flow". This compensation is supported by interlayer branch changes: vertical branches decrease while oblique branches become relatively dominant. It maintains macular blood flow and central vision, helping distinguish normal aging from pathological vascular damage.