Retinal Oxygen Metabolism in Patients With Type 2 Diabetes and Different Stages of Diabetic Retinopathy

Abstract

The aim of the present study was to assess retinal oxygen metabolism in patients with type II diabetes and different stages of non-proliferative diabetic retinopathy (DR) and compare these findings to healthy controls. For this purpose, 67 patients with type II diabetes and 20 healthy controls were included in this cross-sectional study. 34 patients had no, 15 had mild and 18 had moderate to severe DR. Retinal oxygen saturation in arteries and veins was measured using the oxygen module of the Retinal Vessel Analyzer (RVA). Total retinal blood flow (TFBF) was measured using a custombuilt Doppler optical coherence tomography system. Retinal oxygen extraction was calculated out of retinal oxygen saturation and TRBF. Arteriovenous difference in oxygen saturation was highest in healthy subjects (34.9±7.5%), followed by patients with no DR (32.5±6.3%) and moderate to severe DR (30.3±6.5%). The lowest values were found in patients with mild DR (27.3±8.0%, p=0.010 vs. healthy subjects). TRBF tended to be higher in patients with no DR (40.1±9.2µl/min) and mild DR (41.8±15.0µl/min) compared to healthy subjects (37.2±5.7µl/min) and patients with moderate to severe DR (34.6±10.4µl/min). Retinal oxygen extraction was the highest in healthy subjects (2.24±0.57µl O2/min), followed by patients with no DR (2.14±0.6µl O2/min), patients with mild DR (1.90±0.77µl O2/min) and patients with moderate to severe DR (1.78±0.57µl O2/min, p=0.040 vs. healthy subjects). These results indicate that retinal oxygen metabolism is altered in patients with type II diabetes. Further, retinal oxygen extraction decreases with increasing severity of DR.

Impaired retinal oxygen metabolism and perfusion are accompanied by plasma protein and lipid alterations in recovered COVID-19 patients

“…Thus, it is reasonable to assume that a capillary dropout and capillary nonperfusion post COVID-19 infection may lead to a decrease of oxygen delivery to the tissue, which is then reflected in the decrease of oxygen extraction as found in the current study. Along this line of thought, a decrease in arterio-venous difference has also been found in other diseases associated with capillary non-perfusion such as diabetes 32 or Alzheimer´s disease 33 . However, to finally prove this hypothesis, methods for the in vivo assessment of oxygen saturation on the level of retinal capillaries would be required, which currently do not exist.…”

“…The strength of our approach is the use of multimodal imaging for the non-invasive in-vivo assessment of ocular perfusion and oxygen metabolism in the retina, which allows us to directly draw conclusions on the microcirculation. We have recently used this approach to assess functional changes in other systemic diseases such as diabetes or multiple sclerosis 32 , 51 . The use of state-of-the-art molecular profiling allowed us to get more insight in the molecular mechanisms that may be responsible for the observed changes in the ocular vasculature and to suggest a new disease model.…”

Neuro-vascular coupling and heart rate variability in patients with type II diabetes at different stages of diabetic retinopathy

“…In this context, it needs to be noted that there is still no general agreement in the literature on blood flow changes in patients with diabetes. Whereas some studies found decreased retinal perfusion in patients with diabetes ( 11 , 12 , 62 , 63 ), others have reported an increase, especially in early stages ( 13 – 15 , 64 ). Thus, further studies are needed to clarify this issue.…”

Ocular microvascular complications in diabetic retinopathy: insights from machine learning

“…Hence, this finding is compatible with previous hemodynamic studies. The retinal oxygen metabolism is altered in DM and oxygen extraction was found to decrease with the worsening of DR severity 33. The resulting hypoxia may initiate retinal dilatation of the SCP to meet the ganglion cell layer’s metabolic demands 34.…”