Ischemic optic neuropathies include any vascular disease of the optic nerve. Anterior ischemic optic neuropathies are classically distinguished from posterior ischemic optic neuropathies by the presence of optic disc edema in the former, and the absence thereof in the latter. Non-arteritic acute anterior ischemic optic neuropathy is the most common ischemic optic nerve disease. Its exact cause remains unknown. A disc at risk (small and crowded optic nerve) is a typical backdrop for the development of non-arteritic ischemic optic neuropathy. There is no curative or preventive treatment. Posterior ischemic optic neuropathy is exceedingly rare, compared to anterior ischemic optic neuropathy. It is more frequent in patients with cardiovascular risk factors or in the perioperative period. There is no treatment. In any case of ischemic optic neuropathy, an arteritic cause must be ruled out urgently through clinical and paraclinical examinations. The most frequent cause is giant-cell arteritis. In this case, emergency treatment with intravenous methylprednisolone is required in order to limit vision loss in the affected eye and to prevent vision loss in the other eye.