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Sam Kushner-Lenhoff, Yuandong Li, Qinqin Zhang, Ruikang K Wang, Xuejuan Jiang, Amir H Kashani; Capillary Flow Characteristics Vary with Hematocrit on SS-OCTA. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2478.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the associations of capillary density and flow with hematocrit, blood pressure and medical comorbidities using OCTA.
A cross-sectional study using 3 x 3 mm SS-OCTA images to measure vessel skeleton density (VSD) and flow (flux) in the superficial retinal layer (SRL). Flux is a relatively new measure that approximates the number of red blood cells moving through a vessel segment per unit time. Complete blood count, blood pressure, self-reported/medical-record based history including diabetes status, hypertension status, hypertensive medication use, cigarette smoking and retinopathy status (including edema) were obtained. A generalized linear mixed-effects model was used to evaluate the relationship with OCTA parameters after considering the correlation between eyes. Least-square means were estimated.
A total of 154 eyes from 83 participants [56 women and 27 men, mean [SD] age, 66.2 (8.9) years, 22 with diabetes, 63 with hypertension] were included. Mean VSD was 0.147 ± 0.009 and mean flux was 0.156 ± 0.016. VSD showed a negative correlation with age (p=.001) and retinopathy (p=.016), but no significant correlation with hematocrit (p=.86) or signal strength (p=.51). Flux showed a positive correlation with hematocrit (p = .006) and signal strength (p<.001), as well as a negative correlation with age (p=.005) and diabetes status (p=.050). These associations remained even after accounting for hypertensive status, and smoking status. Mean flux was 0.010 lower in OCTA scans with a signal strength of 9 compared with those with a strength of 10, and 0.006 lower for the following comparisons: participants age 65 and above with younger participants, participants having hematocrit of less than 40% with those having higher hematocrit, and diabetics with non-diabetics. A one percent decrease in hematocrit was approximately equivalent to 1.8 years of aging in its effect on the calculated flux.
Retinal blood flow is independently affected by hematocrit and diabetes status even when accounting for known determinants of capillary density such as age and retinopathy status. This effect by hematocrit is not found in OCTA measurements of vessel skeletal density.
This is a 2021 ARVO Annual Meeting abstract.
Vessel flux from the right eyes of two female participants with OCTA image signal strength of 10.
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