Rationale: The term neurovascular coupling refers to the vascular response to an increased neuronal activity. The contact of the nerve terminals to the cortical blood vessels is mostly realized through astrocytes. A major defining property of glaucoma, cupping of the optic disc, implies tissue remodeling of the optic nerve head and involves an astrocytic responses. A malfunction of the astrocytes in glaucoma may lead not only to the hallmark of glaucoma, cupping and death of retinal ganglion cells, but also to an accompanying or even preceding disturbance in ocular neurovascular coupling. The retinal vascular bed was chosen because of the high reproducibility of the dynamic retinal vessel diameter analysis and because recently the hypoxia-inducible factor 1α was found not only in the glia of the optic nerve head but also in the retina of glaucomatous donor eyes and predominantly in retinal locations closely concordant with the locations of visual field defects recorded in these eyes, raising questions about the site of primary damage in glaucoma. It is hoped that this research project will help provide a workable tool and a model able not only to identify a risk factor for glaucoma, but in the future to explore possible therapeutic avenues to modify the course of the disease.