Chang and colleagues examined the associations between peripapillary vessel density (VD) measurements of OCT angiography (OCTA) and multiple systemic factors (age, sex, diagnosis of hypertension, presence and duration of diabetes mellitus, haemoglobin A1c, body mass index, blood pressure, use of antihypertensive medication, history of heart failure or stroke and smoking status) in 1029 eyes of 1029 healthy African American subjects from a population-based cross-sectional study.
Only 1556 OCTA scans of 4135 scans acquired (37.6%) were of acceptable quality and could be included in the analysis. This highlights that image quality continues to be a limitation of the OCTA technology. The strongest influence on VD measurements was the signal strength (SS) of the scans; VD measurements increased significantly with increase in SS.
The magnitude of effect of the systemic factors on the peripapillary VD measurements become clinically insignificant
Using multivariate analysis and controlling for the SS of OCTA scans, they found that older age, male sex and longer duration of diabetes were associated with a statistically significant reduction in peripapillary VD (p < 0.05). Peripapillary VD decreased by 1.2% per decade of increasing age and by 0.2% per five years of increasing duration of diabetes. Peripapillary VD was on an average 0.7% lesser in men compared to women. The study concluded that these systemic factors should be considered while interpreting peripapillary VD changes in glaucoma.
However, one should note that although the associations between peripapillary VD and these three systemic factors were statistically significant, the magnitude of associations were small. Additionally, a previous study using OCTA system from a different manufacturer, has shown that coefficient of repeatability of average peripapillary VD measurements is as high as 3%; thus, a change in peripapillary VD of 3% is within the test-retest variability of OCTA.1 If the result of the study by Chang et al. is interpreted in the background of the test-retest variability of VD measurements, the magnitude of effect of the systemic factors on the peripapillary VD measurements become clinically insignificant.