Primary open-angle glaucoma is a multifactorial disease with a lot of different risk factors. Beside the fact that intraocular pressure (IOP) is the most important risk factor, the reduction of IOP alone is in most cases not sufficient to stop the progression of glaucoma. Therefore, other risk factors play also an important role. One of them is arterial hypertension, the most common systemic disease in glaucoma patients. Arterial hypertension increases IOP slightly, but has an important negative effect on ocular perfusion. Especially the endothelial dysfunction with a disturbed retinal autoregulation plays an important role. Therefore, ischaemic and reperfusion effects alter the optic nerve head and have negative input to the glaucomatous optic neuropathy. In future glaucoma patients should be monitored by ophthalmologists as well as by general physicians/cardiologists to optimise their treatment and to stabilise their glaucoma as well as possible.