OCTA Derived Vessel Skeleton Density Versus Flux and Their Associations With Systemic Determinants of Health

Abstract

Purpose: To examine the associations of optical coherence tomography angiography (OCTA)-derived retinal capillary flux with systemic determinants of health.

Methods: This is a cross-sectional study of subjects recruited from the African American Eye Disease Study. A commercially available swept-source (SS)-OCTA device was used to image the central 3 × 3 mm macular region. Retinal capillary perfusion was assessed using vessel skeleton density (VSD) and flux. Flux approximates the number of red blood cells moving through vessel segments and is a novel metric, whereas VSD is a previously validated measure commonly used to quantify capillary density. The associations of OCTA derived measures with systemic determinants of health were evaluated using multivariate generalized linear mixed-effects models.

Results: A total of 154 eyes from 83 participants were enrolled. Mean VSD and flux were 0.148 ± 0.009 and 0.156 ± 0.016, respectively. In a model containing age, systolic blood pressure, diabetes status, hematocrit, and presence of retinopathy as covariates, there was a negative correlation between VSD and age (P < 0.001) and retinopathy (P = 0.02), but not with hematocrit (P = 0.85) or other factors. There was a positive correlation between flux and hematocrit (P = 0.02), as well as a negative correlation for flux with age (P < 0.001), systolic blood pressure (P = 0.04), and diabetes status (P = 0.02). A 1% decrease in hematocrit was associated with the same magnitude change in flux as ∼1.24 years of aging. Signal strength was associated with flux (P < 0.001), but not VSD (P = 0.51).

Conclusions: SS-OCTA derived flux provides additional information about retinal perfusion distinct from that obtained with skeleton density-based measures. Flux is appropriate for detecting subclinical changes in perfusion in the absence of clinical retinopathy.

Figure 1.

Vessel flux and skeletal vessel map from the right eyes of two female participants with OCTA image signal strength of 10 and hematocrit values spanning the normative range from the cohort of subjects in this study. Note that the subject with the higher hematocrit value demonstrates a relatively higher flux value than skeleton density value.

Figure 2.

Least square mean estimates for select elements of the complete VSD and flux models.