Variability of Retinal Oxygen Metrics in Healthy and Diabetic Subjects

Abstract

Purpose Previous studies have reported alterations in total retinal blood flow (TRBF), oxygen delivery (DO 2 ), oxygen metabolism (MO 2 ), and oxygen extraction fraction (OEF) due to retinal diseases. The purposes of the current study were to determine variabilities and establish normal confidence intervals (CIs) for these metrics. Methods A total of 22 healthy and 14 diabetic subjects participated in the study. Retinal vascular oxygen saturation (SO 2 ) and TRBF were measured by oximetry and Doppler optical coherence tomography, respectively. DO 2 , MO 2 , and OEF were calculated from SO 2 and TRBF measurements. Means, standard deviations (SDs), and CIs of metrics were determined in healthy subjects. Intra-visit variability was determined by the mean SDs of repeated measurements. Inter-visit variability was determined by the difference of measurements between two visits. Results TRBF was 44 ± 15 µL/min (95% CI, 37–51) in healthy subjects. Intra-visit variabilities of TRBF were 5 µL/min and 6 µL/min in healthy and diabetic subjects, respectively. Inter-visit variability of TRBF was 3 µL/min in diabetic subjects. DO 2 , MO 2 , and OEF were 8.3 ± 2.9 µLO 2 /min (95% CI, 7.0–9.6), 3.2 ± 0.9 µLO 2 /min (95% CI, 2.8–3.6), and 0.40 ± 0.08 (95% CI, 0.36–0.43), respectively, in healthy subjects. Inter-visit variabilities of DO 2 , MO 2 , and OEF were 0.6 µLO 2 /min, 0.1 µLO 2 /min, and 0.03, respectively, in diabetic subjects. Conclusions The findings established variabilities and normal baselines for TRBF, DO 2 , MO 2 , and OEF measurements in a small cohort of subjects. Translational Relevance The variability and normal baselines of retinal oxygen metrics may be useful for diagnosing and monitoring patients with retinal diseases.