Retinal Vessel Oxygen Saturation under Flicker Light Stimulation in Patients with Nonproliferative Diabetic Retinopathy

Abstract

PURPOSE. We investigated the response of retinal vessel diameters and oxygen saturation to flicker light stimulation of neuronal activity in patients with diabetic retinopathy. METHODS.We included 18 patients with nonproliferative diabetic retinopathy (mean age 62.2 6 8.3 years, diabetes type 1 in 4 patients and type 2 in 14, hemoglobin A1c 7.7 6 0.9%, duration of diabetes 24.1 6 9.3 years) and 20 agematched healthy controls (age 66.7 6 10.3 years). Dual wavelength (548 and 610 nm) fundus images were taken before and during luminance flicker stimulation (12.5 Hz, modulation depth > 1:25) for 90 seconds. Diameters (central retinal arterial [CRAE] and venous [CRVE] equivalents) and oxygen saturation (SO 2 ) were determined, and averaged for all arterioles and venules in an annular area centered at the optic disk.RESULTS. Flicker light increased CRAE, CRVE, and venous SO 2 by 0.6 6 6.6%, 2.7 6 6.1%, and 2.0 6 2.4% (P < 0.05), respectively, in the patients as well as 4.7 6 8.4% (P < 0.05), 8.7 6 5.2% (P < 0.05), and 4.2 6 3.5% (P < 0.05), respectively, in the controls. The arterial SO 2 remained unchanged in both groups. The increase of the venous SO2 correlated significantly (P ¼ 0.027) with that of the CRAE. There was a trend (P ¼ 0.06) for lower increase of the venous SO 2 with higher body mass index. CONCLUSIONS.Our results support the thesis of an impaired regulation of oxygen supply to the diabetic retina. Whereas in healthy subjects the stimulation of neuronal activity increases the vascular diameters and, subsequently, the oxygen supply, this increase is reduced in diabetic retinopathy. This may hint at the role of endothelial dysfunction in the etiology of the disease. (Invest Ophthalmol Vis Sci.

Blood flow mechanics and oxygen transport and delivery in the retinal microcirculation: multiscale mathematical modeling and numerical simulation

“…In contrast, a decrease in O 2 tension (hypoxia) induces a dilation of the retinal arterioles and an increase in blood flow (Eperon et al 1975;Pournaras et al 2008 (Weinreb and Harris 2009). Several studies have shown that the vasodilation response to flicker stimulation is impaired in pathological conditions, including glaucoma (Ramm et al 2014), diabetic retinopathy (Hammer et al 2012) and vasospastic propensity (Gugleta et al 2006). Our model suggests that the observed vasodilation in the retinal arterioles might be due to an O 2 -mediated response (Arciero et al 2013;Pournaras et al 2008).…”

The clinical implications of recent studies on the structure and function of the retinal microvasculature in diabetes

“…In addition, retinal oxygen tone is tightly controlled by autoregulation of the vessel diameters [95]. These data, together with impaired flicker light-induced vasodilation in diabetes, lend support to the hypothesis of an impaired regulation of oxygen supply to the diabetic retina [96].…”

Measurement of Retinal Oxygen Saturation in Patients with Chronic Obstructive Pulmonary Disease

“…8 Briefly, fundus images with the optic nerve head in center were taken. Oxygen saturation was measured in all vessels in a peripapillary annulus, with an inner radius of 1 and an outer radius of 1.5 disc diameters and averaged over all arterioles and venules.…”