Ischemic optic neuropathy refers to an acute malnutrition disease in which the nutrient vessels of the optic nerve have circulatory disorders. Generally, the boundary is the point where the central retinal artery enters the optic nerve about 9 to 11 mm behind the bulb. It is clinically divided into two types: anterior and posterior ischemic optic neuropathy. Circulatory disorders in the posterior ciliary artery that supplies the optic disc cause acute ischemia and hypoxia of the optic disc, resulting in optic disc edema. Not only the optic disc, but also the cribriform plate and the nerve fibers behind the cribriform plate can be affected, which is called anterior ischemic optic neuropathy (AION). Ischemic changes occur from the intraorbital segment of the optic nerve to the optic chiasm, which is called posterior ischemic optic neuropathy (PION), without optic disc edema.