Retinal oxygen metabolism and neuro-vascular coupling in patients with type II diabetes at different stages of diabetic retinopathy

Abstract

Purpose : The aim of the present study was to assess retinal oxygen metabolism and neurovascular coupling (NVC) in patients with type II diabetes at different stages of non-proliferative diabetic retinopathy (DR) and compare these findings to healthy controls.

Methods : To assess oxygen metabolism 67 patients with type II diabetes and 20 healthy controls were included in this cross-sectional study. 34 patients with diabetes had no DR, 15 patients had mild DR and 18 patients had moderate to severe DR. To measure retinal oxygen saturation in arteries and veins the oxygen module of a Retinal Vessel Analyzer was used. A custom-built Doppler optical coherence tomography (DOCT) system was used to assess total retinal blood flow (TRBF). Values of oxygen saturation and TRBF were used to calculate retinal oxygen extraction. To assess retinal blood flow before and during visual stimulation to measure hyperemic response combined measurement of retinal vessel calibers and blood velocity by the means of DOCT was used. For these measurements 76 subjects, of which 56 had diabetes at different stages of DR and 20 healthy controls were included.

Results : 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). TRBF was highest in patients with no DR (40.1 ± 9.2 μL/min) and mild DR (41.8 ± 15.0 μL /min) compared to healthy subjects (37.2 ± 5.7 μl/min) and patients with moderate to severe DR (34.6 ± 10.4 μl/min). Flicker responses in patients with DR were significantly decreased depending on the stage of DR. (no DR 37.7 ± 26.0%, mild DR 26.2 ± 28.2%, moderate to severe DR 22.3 ± 13.9%; p = 0.035, ANOVA).

Conclusions : Our results show that retinal oxygen extraction decreases with increasing severity of DR. With regard to flicker induced hyperemia, the present study indicates that patients with DR show a reduction compared to healthy subjects.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.