Retinal Vascular Response to Hyperoxia in Patients with Diabetes Mellitus without Diabetic Retinopathy

Abstract

Purpose. To evaluate the retinal vascular response to hyperoxia in patients with diabetes at the preclinical stage of diabetic retinopathy (DR) and to quantify the changes in comparison with normal subjects using optical coherence tomography angiography (OCTA). Methods. In this prospective study, 40 eyes of 20 participants comprising 10 diabetic patients with no diabetic retinopathy (NDR) and 10 normal subjects were recruited. OCTA images were acquired in the resting position and were repeated after a hyperoxic challenge using a nasal mask connected to a reservoir bag supplying 100% oxygen at the rate of 15 L per minute for 5 minutes. The changes of mean parafoveal vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), the foveal avascular zone (FAZ) size, and the outer retina flow index were compared between two conditions in each group and between the two study groups. The statistical significance of differences in the means was evaluated using Student’s t-test for unpaired samples with consideration of the generalized estimating equations (GEE) for intereye correlation. Results. At baseline, the mean parafoveal VD of SCP and DCP were significantly lower in the NDR participants compared to the healthy subjects (P < 0.001 and P = 0.006, respectively). After induction of the hyperoxic challenge in healthy participants, mean parafoveal VD reduced at both the SCP and DCP, but reached a statistical significance only in DCP (P = 0.006). However, following induction of hyperoxic challenge in patients with NDR, no significant decline was noticed in mean parafoveal VD of SCP and DCP. The degree of change in mean parafoveal VD of DCP was statistically significantly more pronounced in healthy subjects compared to the NDR group (P = 0.034). The change in FAZ size and the outer retina flow index were comparable between the two study groups. Conclusion. Retinal capillary layers responded differently to hyperoxia-induced challenge, and in normal subjects, the autoregulatory mechanism was mostly effective in the parafoveal DCP. Retinal vascular reactivity was impaired in SCP and DCP at the preclinical stage of DR. OCTA as a noninvasive modality was able to quantify the retinal vascular response to the hyperoxic challenge.

Optical Coherence Tomography Angiography Changes in Diabetic Macular Ischemia after Systemic Normobaric Oxygen Therapy

“…The increase in foveal SCP VD failed to reach the signi cance level (P = 0.059) which could be attributed to small sample size. In a study evaluating retinal vascular response to hyperoxia, normal individuals showed a reduction in parafoveal DCP VD due to autoregulatory mechanisms, however, in diabetic patients without retinopathy such a reduction was not observed [30]. Impaired autoregulation might have a role in the increased VD observed in patients with DMI in our study which ultimately might be bene cial in these patients.…”

“…Several studies have shown the effects of supplemental oxygen on retinal function or structure in diabetic patients with [10-12, 31, 32] or without retinopathy [30] and other retinal ischemic conditions [19,33] or retinal vascular occlusions [34][35][36].…”

“…Although retinal vascular response to hyperoxic state differs in diabetic patients compared to healthy individuals [30], hyperoxia may favorably affect DMI by increasing the amount of oxygen dissolved in the plasma and thereby increasing the oxygen gradient between the blood and retina to transfer more oxygen to the tissue. Additionally, oxygen-induced vasoconstriction decreases retinal edema and thereby decreases the distance for oxygen to diffuse which ameliorates ischemia and improves retinal function.…”

The Anatomic and Functional Outcomes of Ozurdex-Aided Vitrectomy in Proliferative Diabetic Retinopathy

“…Studies have proved that compared with normal people, the vessel density of SCP and DCP in the early stage of DR will decrease, reflecting the vascular injury in the early stage of DR, and with the progress of DR, a large range of nonperfusion areas may eventually appear in the retina. 32 At the same time, compared with SCP, DCP and DVP can better reflect the vascular changes of DR, and the injury time is longer, which makes some non-perfusion areas irreversible. [33][34][35] There were no statistical differences for SVP, ICP and DCP of the three groups in this study, probably because patients who have developed PDR requiring surgery have irreversible damage to the fundus microvascular circulation and injectable drugs do not improve retinal microcirculation in the short term.…”

Advances in Structural and Functional Retinal Imaging and Biomarkers for Early Detection of Diabetic Retinopathy

“…Safi et al assessed the retinal vascular response to hyperoxia in patients with diabetes at the pre-clinical stage of DR and compared it with normal controls. They found that impaired retinal vascular reactivity was apparent at this stage, with disturbances in the autoregulatory mechanism particularly pronounced in the parafoveal DCP [121]. This finding further underscored that the DCP experiences more severe microvascular damage than the SCP in patients with DM or DR at the early stage [122].…”