Key result
Flicker-induced retinal blood flow hyperemia was significantly reduced in patients with type II diabetes depending on the severity of diabetic retinopathy, ranging from 40.4% in healthy controls to 22.3% in moderate to severe DR.
Why the study?
The extent to which functional hyperemia is altered across different stages of diabetic retinopathy in type II diabetes was largely unknown.
Is flicker-induced retinal hyperemia and heart rate variability altered in patients with type II diabetes at different stages of diabetic retinopathy compared to healthy controls?
Cross-Sectional (n=76)
Observer-blinded
No
Is flicker-induced retinal hyperemia and heart rate variability altered in patients with type II diabetes at different stages of diabetic retinopathy compared to healthy controls?
Absolute Event Rate: 22.3% vs 40.4%
p-value: p=0.035
Flicker-induced retinal hyperemia is progressively impaired in patients with type II diabetes as the severity of diabetic retinopathy increases.
Impaired retinal hyperemia may signal microvascular dysfunction in diabetes; leaves open its role as a DR severity biomarker pending larger trials.
Aims/Hypothesis There is evidence that diabetes is accompanied by a break-down of functional hyperemia, an intrinsic mechanism of neural tissues to adapt blood flow to changing metabolic demands. However, to what extent functional hyperemia is altered in different stages of diabetic retinopathy (DR) in patients with type II diabetes is largely unknown. The current study set out to investigate flicker-induced retinal blood flow changes in patients with type II diabetes at different stages of DR. Materials and methods A total of 76 subjects were included in the present parallel-group study, of which 56 had diabetes with either no DR or different stages of non-proliferative DR ( n = 29 no DR, 12 mild DR, 15 moderate to severe DR). In addition, 20 healthy subjects were included as controls. Retinal blood flow was assessed before and during visual stimulation using a combined measurement of retinal vessel calibers and blood velocity by the means of Doppler optical coherence tomography (OCT). To measure systemic autonomic nervous system function, heart rate variability (HRV) was assessed using a short-term orthostatic challenge test. Results In healthy controls, retinal blood flow increased by 40.4 ± 27.2% during flicker stimulation. Flicker responses in patients with DR were significantly decreased depending on the stage of the disease (no DR 37.7 ± 26.0%, mild DR 26.2 ± 28.2%, moderate to severe DR 22.3 ± 13.9%; p = 0.035, ANOVA). When assessing systemic autonomous neural function using HRV, normalized low frequency (LF) spectral power showed a significantly different response to the orthostatic maneuver in diabetic patients compared to healthy controls ( p < 0.001). Conclusion/Interpretation Our study indicates that flicker induced hyperemia is reduced in patients with DR compared to healthy subjects. Further, this impairment is more pronounced with increasing severity of DR. Further studies are needed to elucidate mechanisms behind the reduced hyperemic response in patients with type II diabetes. Clinical trial registration [ https://clinicaltrials.gov/ ], identifier [NCT03 552562].
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Hommer et al. (2022) conducted a cross-sectional in Type II diabetes and diabetic retinopathy (n=76). Diabetic retinopathy severity (Type II diabetes) vs. Healthy controls was evaluated on Flicker-induced retinal venous blood flow increase (p=0.035). Flicker-induced retinal blood flow hyperemia was significantly reduced in patients with type II diabetes depending on the severity of diabetic retinopathy, ranging from 40.4% in healthy controls to 22.3% in moderate to severe DR.
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