Altered nitric oxide system in patients with open-angle glaucoma

Objective: To investigate the ocular blood flow response to systemic nitric oxide synthase inhibition in patients with primary open-angle glaucoma. Methods: In 12 patients with glaucoma and 12 age-matched control subjects, subfoveal choroidal blood flow, optic nerve head blood flow, ocular fundus pulsation amplitude, intraocular pressure, and systemic hemodynamic parameters were measured at baseline and after inhibition of nitric oxide synthase by intravenous administration of NG-monomethyl-L-arginine. Results: The increase in blood pressure in response to NG-monomethyl-L-arginine was comparable between the 2 study cohorts. In patients with glaucoma, the decrease of optic nerve head blood flow (P=.03) and fundus pulsation amplitude (P<.001) during nitric oxide synthase inhibition was significantly less pronounced than in healthy control subjects. A tendency toward a reduced response in choroidal blood flow was seen (P=.051 between groups) in patients with glaucoma. Conclusions: This is the first in vivo study providing evidence for an altered ocular L-arginine/nitric oxide system in patients with glaucoma. Normalization of the ocular nitric oxide production may be beneficial in terms of normalization of ocular blood flow and neuroprotection of retinal ganglion cells.