Background : Glaucoma is a common disease, potentially blinding, characterized by progressive damage to the optic nerve. If the intraocular pressure is the most known risk factor, however, there are cases of glaucoma scalable despite well-controlled intraocular pressure, ocular hypertension without glaucoma or glaucoma without ocular hypertension (normal tension glaucoma).

Purpose :Involvement of vascular factors in the development of glaucoma and scalability has been proved, associated with a possible loss of vascular autoregulation. The objective of this study is to quantify MRI flow of blood flows referred ophthalmic patients with glaucoma untreated comparison with control subjects.

Eye vascularization, supplied by ophthalmic artery and superior ophthalmic vein is not easily accessible to routine explorations to date. Similarly the potential oscillations of the cerebrospinal fluid (CSF) around the optic nerve have not been described. Developments in magnetic resonance imaging (MRI) provide new insights into the quantitative study of blood and CSF flows through phase contrast MRI also called "flow MRI". Our hypothesis is that the ability of MRI to measure intracranial flow is applicable to the vasculature of the eye.

The MRI protocol will be applied to control adult subjects previously examined by an ophthalmologist. Structures to be imaged will be identified on a morphological sequence. Each MRI phase contrast slice (flow MRI) will be positioned perpendicularly to the flow direction. The flow MRI data will be analysed by a dedicated image processing tool which performs the vessels segmentation. For each curve of the vessel flow evolution during the cardiac cycle is reconstructed.

Glaucomatous patients will undergo a six-month follow-up to determine if they respond to their therapy.

Inclusion Criteria:

• Adult participants
• Diagnosis of primary open angle glaucoma or normal-tension glaucoma
• Never received any anti glaucoma therapy
• Patients included in the group " normal pressure glaucoma " are patients where the diagnosis of optic neuropathy have been worn by the ophthalmologist with measured intraocular pressure <21 mmHg.
• Healthy controls will be examined by an ophthalmologist before inclusion

Exclusion Criteria:

• Anyone with a classic contraindication to MRI
• Cardiovascular comorbidities or neurovascular : uncontrolled systemic hypertension , Diabetes, heart failure , carotid stenosis , ischemic stroke or transient ischemic attack.
• Already treated glaucoma
• Prescription by the ophthalmologist another treatment than prostaglandin analogue treatment.
• Other clinical forms of glaucoma : angle closure glaucoma, neovascular glaucoma, exfoliative glaucoma, secondary glaucomas, pigment dispersion glaucoma, traumatic glaucoma, congenital glaucoma
• Presence of other ocular pathology (simple refractive error allowing 10/10 of best corrected visual acuity and mild and moderate cataracts will not be considered as a criterion for non- inclusion).
• History of intraocular or orbital surgery of less than 6 months .