Abstract
Purpose :
Previous studies have reported alterations in total retinal blood flow (TRBF), oxygen delivery (DO2), oxygen metabolism (MO2), and oxygen extraction fraction (OEF) due to various retinal diseases. The purposes of the current study were to determine intra- and inter-visit variabilities and establish normal 95% confidence intervals (CIs) for these metrics.
Methods :
Twenty-two non-diabetic healthy and 14 diabetic subjects diagnosed with either no diabetic retinopathy (DR) or untreated mild non-proliferative DR participated in the study. Imaging was performed at one visit in healthy subjects and two visits in diabetic subjects. Retinal vascular oxygen saturation (SO2) and multiple TRBF measurements were obtained using our oximetry system and Doppler optical coherence tomography, respectively. DO2, MO2, and OEF were calculated from SO2 and mean TRBF. Intra-visit variability of TRBF was determined by the standard deviation (SD) of multiple measurements, averaged over data in each group. Normal 95% CIs for all metrics were determined in healthy subjects. Inter-visit variability was determined by the difference between measurements at two visits (6 ± 3 months apart), averaged over data in diabetic subjects.
Results :
Intra-visit variability of TRBF measurements was 8 μl/min in both healthy and diabetic subjects. Mean TRBF was 44 ± 15 μL/min (CI: 37 to 51) in healthy subjects. Inter-visit variability in mean TRBF was 3 μL/min (CI: -1 to 8) in diabetic subjects. DO2 and MO2 were 8.3 ± 2.9 μLO2/min (CI: 7.0 to 9.6) and 3.2 ± 0.9 μLO2/min (CI: 2.8 to 3.6) in healthy subjects, respectively. In diabetic subjects, inter-visit variabilities of DO2 and MO2 were 0.6 μLO2/min (CI: -0.3 to 1.5) and 0.1 μLO2/min (CI: -0.7 to 0.5), respectively. OEF was 0.40 ± 0.08 (CI: 0.36 to 0.43) in healthy subjects. Inter-visit variability in OEF was 0.03 (CI: -0.09 to 0.02) in diabetic subjects. Mean TRBF, DO2, MO2, and OEF measurements obtained at both visits in diabetic subjects were within normal CIs and not significantly different than those in healthy subjects (P > 0.30). There was an inverse correlation between mean TRBF and age in healthy subjects (r = -0.45; P = 0.03, N=22).
Conclusions :
The findings established variabilities and normal baselines for TRBF, DO2, MO2, and OEF measurements, providing a basis for detecting and monitoring changes due to diseases.
This is a 2021 ARVO Annual Meeting abstract.