Correlation of flicker-induced and flow-mediated vasodilatation in patients with endothelial dysfunction and healthy volunteers

OBJECTIVE - Flicker-induced vasodilatation is reduced in patients with vascular-related diseases, which has at least partially been attributed to endothelial dysfunction of retinal vessels. Currently, the standard method to assess endothelial function in vivo is flow-mediated vasodilatation (FMD). Thus, the present study was performed to investigate whether a correlation exists between flicker-induced vasodilatation and FMD in patients with known endothelial dysfunction and healthy subjects. RESEARCH DESIGN AND METHODS - In the present study, 20 patients with type 1 diabetes, 40 patients with systemic hypertension (systolic blood pressure 140-159 mmHg; diastolic blood pressure 90-99 mmHg) and/or serum cholesterol levels ≥0.65 mmol/l, and 20 healthy control subjects were included. The flicker response was measured using the Dynamic Retinal Vessel Analyzer. FMD was determined using a high-resolution ultrasound system, measuring brachial artery diameter reactivity during reperfusion after arterial occlusion. RESULTS - The flicker response of both retinal arteries and veins was significantly reduced in the two patients groups. Likewise, FMD was significantly reduced in patients compared with healthy control subjects. However, only a weak correlation between flicker-induced vasodilatation and FMD was observed. CONCLUSIONS - The study confirms that flicker responses and FMD are reduced in the selected patient groups. Whether the weak correlation between FMD and flicker is due to the different stimulation type, the different vascular beds measured, or other mechanisms has yet to be investigated.