Abstract. Following the hypothesis that chronic ischemia is the main cause of functional deficiency in glaucoma, a double blind clinical experiment was carried out to study the effect of hyperbaric oxygenation in 51 glaucoma subjects, of which 31 were in the experimental group and 20 in the control group. In the experimental group there was a significant improvement of visual fields (p < 0.05), whereas there was no change in the subjects in the control group. Hyperbaric oxygen did not have any influence on intraocular pressure. The achieved visual field improvements remained stable for 3 months (p < 0.05), except for I, and I, isopters of the left eye and I, isopter of the right eye, while they were considerably reduced after 6 months (p > 0.05).