Abstract
Abstract: :
Purpose: There is evidence of an altered L–arginine/nitric oxide (NO) system in patients with open angle glaucoma. A direct in vivo evidence of this hypothesis is, however, lacking. In the present study we hypothesized that patients with open angle glaucoma may have an abnormal response of ocular blood flow parameters to systemic infusion of L–NMMA, an inhibitor of NO synthase, as compared to healthy age–matched control subjects. Methods: Twelve patients with primary open angle glaucoma and 12 healthy age– and sex–matched control subjects were included in this study. Ocular hemodynamic parameters, blood pressure and intraocular pressure (IOP) were measured before and after infusion of L–NMMA in a dosis of 3 mg/kg over 5 minutes. Optic nerve blood flow (ONHBF) and subfoveal choroidal blood flow (CHBF) were measured with laser Doppler flowmetry. In addition, ocular fundus pulsation amplitude (FPA) was measured with laser interferometry to assess pulsatile choroidal blood flow. Results: In both study cohorts L–NMMA caused a comparable increase in blood pressure, but did not change IOP. In healthy control subjects L–NMMA caused a decrease in ONHBF (–12%, p < 0.001), in CHBF (–15%, p = 0.003) and FPA (–15%, p < 0.001). The response in ONHBF (–5%; p = 0.03 versus healthy controls) and FPA (–7%; p = 0.03 versus healthy controls) was significantly diminished in patients with open angle glaucoma. The response in CHBF (–10%; p = 0.051 versus healthy controls) tended to be reduced. Conclusions: The data of the present study show that patients with open angle glaucoma have an abnormal response to L–NMMA at the level of the ocular circulation indiating an abnormal L–arginin/NO system.
Keywords: nitric oxide • blood supply • optic disc