Regional and Layer Specific Retinal Capillary Red Blood Cell Velocimetry in Healthy Human Subjects

To investigate retinal capillary and choriocapillaris red blood cell (RBC) velocity using optical coherence tomography angiography (OCTA)-based velocimetry in healthy human subjects.

This was a cross-sectional, observational study using a 1050-nm swept-source OCTA instrument with a new M-B scan protocol to obtain 2 × 2-mm2 volumes in the central, nasal, and temporal macula regions. An eigendecomposition-based analysis estimated the average mean frequency (MF) of moving particles in the radial peripapillary capillaries (RPCs), superficial retinal layer (SRL), deep retinal layer (DRL), and choriocapillaris (CC) in each region. MF is linearly proportional to RBC velocity. A linear mixed model evaluated the effect of retinal layer and region on MF.

Sixty-five subjects (median age, 46 years; interquartile range, 27-67; 97 eyes, 54% females) were included in the study. MF values for SRL, DRL, and CC among all regions were 166 ± 44, 106 ± 36, and 313 ± 33Hz, respectively (P < 0.05). The lowest MF was in the RPCs (133 ± 41; P < 0.001). There were significant differences in MFs between age groups, as well as all layers within and across different regions (P < 0.05). In the central macula, there was a correlation between MF and age in the SRL, DRL, and CC (r = -0.581, -0.439, and -0.658, respectively; P < 0.001). Weaker associations were noted in the peripapillary and temporal retina.

Retinal and choriocapillaris RBC velocity varies with age, layer, and retinal region. These variations may provide insight into vascular aging and blood flow regulation.

Age-related and regional changes in capillary and choriocapillaris RBC velocity are important for understanding retinal vascular health and disease.