 Day 1: First, MRI scans on the brain to measure the blood flow of OA as well as the structural and morphological properties of the ON see method below. Second, just after MRI examination, the patient will be examined at the Department of ophthalmology. Measurement of intraocular pressure, ocular pulse amplitude, central corneal thickness, bulb length, investigation with optical coherence tomography OCT and blood pressure will be performed. The patients from G3 Normal Pressure Glaucoma will participate only in Day 1, since most cases already has pressure-lowering treatment. Also subjects in G4 vill only participate in Day 1. All other participants will receive pressure lowering drug Latanoprost in one eye once daily, until the protocol is repeated at Day 2. 