Increased vascular resistance in cervical arteries is associated with elevated resistance in retinal vessels and capillaries in patients with type 2 diabetes and may be associated with the development of retinopathy, according to study results published in Diabetes Research and Clinical Practice.

Using laser speckle flowgraphy, investigators aimed to determine the relationship between blood flow in retinal vessels and capillaries, blood flow in cervical arties, and the development of retinopathy in patients with type 2 diabetes.

Retinal blood flow in the optic nerve head was measured using laser speckle flowgraphy and used to calculate the resistivity indices of the retinal vessel and capillaries. An elevated resistivity index indicated increased vascular resistance. Carotid and vertebral artery flow were assessed by Doppler ultrasonography.

Of 110 patients (40.9% women) included in the study, 27 had mild nonproliferative diabetic retinopathy. Clinical parameters and patient characteristics were similar between patients with and without retinopathy, though patients with retinopathy tended to have a longer duration of diabetes (12.2 vs 8.1 years; P =.008) and higher hemoglobin A1c levels (10.2% vs 9.5%; P =.045) than those without diabetic neuropathy.


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The resistivity of the common carotid artery was associated with resistivity in both retinal vessels (correlation coefficient [r] =0.257; P =.007) and retinal capillaries (r =0.283; P =.003). Internal carotid artery flow was also associated with retinal vessel (r =0.450; P <.001) and capillary flow (r =0.503; P <.001).

Vertebral artery flow was associated with resistivity in retinal vessels (r =0.427; P <.001) and capillaries (r =0.433; P <.001) as well.

Independent of other explanatory variables, including age and diabetes, retinal blood vessel flow was related to blood flow in the common carotid (regression coefficient [β]=0.189, P =.013), internal carotid (β=0.208; P =.011), and vertebral arteries (β=0.167; P =.032). The correlation with cervical artery flow was even higher for retinal blood capillaries (common carotid: β=0.250; P =.002; internal carotid: β=.312; P <.001; vertebral: β=0.203; P =.015).

The investigators noted that the cross-sectional nature of the study prevented the verification of a causal relationship between retinal and cervical hemodynamics.

“Patients with high vascular resistance of the carotid and vertebral arteries, may also have high vascular resistance of the retinal microcirculation,” the study authors concluded. “Such patients should be carefully followed to detect retinopathy development.”

Reference

Sawada S, Tsuchiya S, Kodama S, et al. Vascular resistance of carotid and vertebral arteries is associated with retinal microcirculation measured by laser speckle flowgraphy in patients with type 2 diabetes mellitus [published online June 2, 2020]. Diabetes Res Clin Pract. doi:10.1016/j.diabres.2020.108240