Progressive Open Angle Glaucoma (OAG) and Ocular Blood Flow

Inclusion Criteria: * Men and women over 40 years * Unilateral or bilateral primary open angle glaucoma (POAG) or normal tension glaucoma (NTG) with visual defect, marked by an AGIS score (1994; 1. Study design and methods and baseline characteristics of study patient) of at least 1 but not more than 16 at the screening visit * At least 3 reliable visual field tests in the eye that will be studied * Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant * Best-corrected visual acuity of 20/40 or better, spherical refraction within ± 3.0 diopters and cylinder correction within ± 3.0 diopters Exclusion Criteria: * Evidence of secondary glaucoma, pseudoexfoliation, pigmentary dispersion * Any form of retinal or neuroophthalmological disease that could result in visual field defects. * Mean IOP \> 30 mmHg, or any IOP \> 35 mmHg in at least one eye * History of acute angle closure * Closed or barely open anterior chamber angle * Topical or systemical/oral therapy with steroids * Standard deviation of visual field testing \> 10 * Ocular inflammation or infection within the last three months * Intraocular surgery or argon laser trabeculoplasty within the last six months * Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study * Treatment in the previous 3 weeks with any drug * Symptoms of a clinically relevant illness in the 3 weeks before the first study day * Blood donation during the previous 3 weeks * Ametropia \> 3 dpt