Objective: We hypothesized that blood flow and arteriolar morphological changes are related to each other in the human retinal vascular bed.

Methods: The study cohort comprised 141 non-diabetic untreated male patients with or without arterial hypertension but without evidence for cardiovascular disease. Retinal capillary blood flow (RCF) before and after exposure to flicker light and to infusion of nitric oxide (NO) synthase inhibitor N-monomethyl-L-arginine (L-NMMA), and parameters of retinal arteriolar morphology, e.g. wall-to-lumen ratio, were assessed non-invasively and in vivo by scanning laser Doppler flowmetry.

Results: Patients were grouped according to their median RCF into two groups. Patients with RCF above the median revealed lower wall-to-lumen ratio compared to patients with RCF equal or below the median (0.30±0.1 vs 0.34±0.1 (−), P adjusted = 0.023). In addition, RCF was inversely related to wall-to-lumen ratio independently of major cardiovascular risk factors (ß=−0.224, P=0.026). In parallel, the change of RCF to L-NMMA was greater in patients with RCF above the median compared to the counter group (−8.95±11 vs. 0.35±15 (%), P adjusted <0.001). The increase in RCF to flicker light, was inversely related to wall-to-lumen ratio in hypertensive but not in normotensive or all patients (r=−0.292, P=0.047, r=−0.035, P=0.746 and r=−0.126; P=0.144, respectively).

Conclusions: In the retinal circulation blood flow and arteriolar morphology are related to each other. Basal NO activity might impact on blood flow and arteriolar remodeling. In hypertensive, but not in normotensive patients, the vasodilatory capacity is inversely related to arteriolar wall-to-lumen ratio in the human retinal vascular bed.