A variety of studies demonstrate that ocular blood flow is altered in glaucoma. Various animal and human studies have shown an increase in retinal and optic nerve head blood flow in response to diffuse luminance flicker. Based on studies with ERG, this effect has been attributed to augmented activity in the retinal ganglion cells and associated axons indicating a coupling mechanism between neuronal activity and retinal blood flow. Whereas a variety of studies have confirmed these effects, the knowledge about this coupling in the retina of patients with glaucoma is sparse.

Recently the investigators could show that flicker induced vasodilatation is blunted in patients with open angle glaucoma. However, the investigators results are limited by the fact that only data about retinal vessel diameters, not blood flow per se, are available. The further development of the investigators current flicker stimulation technique now allows us to determine blood flow velocity during flicker stimulation. Thus, in the current study, the investigators set out to determine whether this blood flow response is impaired in patients with glaucoma as compared to those in healthy volunteers and whether this is related to altered neural activity.

The study objective was, to investigate whether the blood flow response to flicker stimulation is altered in patients with glaucoma.

Inclusion Criteria:

• Men and women aged between 20 and 80 years.
• Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant.
• Inclusion criteria of patients are open angle glaucoma.
• Men and women will be included in equal parts. A pregnancy test will be performed at screening.
• Ametropia of less than 3 diopters and anisometropia of less than 1 diopter.

Exclusion Criteria:

• Treatment with vasoactive drugs.
• Presence of intraocular pathology other than open angle glaucoma.
• Presence of ocular hypertension or PEX (pseudoexfoliation) glaucoma
• History or family history of epilepsy.
• Pregnancy.
• Diabetes mellitus.