Microvascular endothelial function and regional differences in vasodilation in the human cutaneous microcirculation in primary open angle glaucoma

ABSTRACT

Objective:Blood flow in the optic nerve head and finger skin are related in subjects with a primary vascular dysregulation (PVD). Since PVD may also occur in glaucoma, the aim of this study was to investigate the responses of the microcirculatory blood flow at the finger and forearm skin to iontophoresis of endothelial-dependent (acetylcholine - ACh) and endothelial-independent (sodium nitroprusside - SNP) vasodilators in primary open angle glaucoma (POAG). Design and Methodology: We studied 22 patients with POAG and 27 control subjects. The vasodilator responses to iontophoresis of ACh and SNP performed at the finger and forearm skin were determined, with skin microcirculatory blood flow being expressed as cutaneous red cell flux (RCF) as measured by Laser Doppler Flowmetry. Results: ACh and SNP induced significant increases in RCF from baseline (p<0.001) at both the finger and forearm skin sites in POAG patients and controls, but there was no difference in vasodilation between the subject groups. Within controls and POAG patients, for both ACh and SNP, the baseline RCF was higher in the finger than in the forearm skin (p<0.05). The vasodilatory response to ACh in the finger was also higher than in the forearm skin (p<0.05) i controls and POAG. The mean vasodilatory response to SNP in the finger was higher than in forearm skin (p<0.05) in controls and POAG. Conclusions: The vasodilatory responses to acetylcholine in POAG suggest normal microvascular endothelial function. The higher baseline RCF and vasodilatory responses in the finger than in forearm skin sites may reflect the difference in vascularity between these sites.