Effects of Non-Specific Endothelin-A Receptor Blockade on Ocular Blood Flow in Patients With Glaucoma.

Several lines of evidence suggest now that ocular perfusion abnormalities may contribute to the progression of glaucoma. It has been hypothesised that increased endothelin-1 plasma levels, as seen in patients with glaucoma, may be related to these alterations in ocular blood flow. We could show in recent experiments that administration of ET-1 decreases ocular blood flow, whereas blocking of the ET-A receptors do not affect basal vascular tone in healthy subjects. In the current study we set out to evaluate the effect Bosentan, a non-selective ETA-receptor antagonist in patients with open-angle glaucoma. This should allow us to test the hypothesis that administration of an ET-1 receptor antagonist increases ocular blood flow in patients with glaucoma.

Investigations will be done with a retinal vessel analyzer to determine retinal vessel cross-sectional diameters, with laser Doppler flowmetry and laser Doppler velocimetry to determine subfoveal macular blood flow and optic nerve head blood flow and with laser interferometric measurements to determine fundus pulsation amplitude in the macula. The intraocular pressure will be measured with applanation tonometry. This will be assessed at baseline and in response to peroral application of Bosentan or placebo.

The study objective is therefor, to evaluate the contribution of ET-1 to ocular blood flow dysregulation in patients with open-angle glaucoma.