Ischemic optic neuropathy should be considered as a possibility in patients older than 40 years of age with sudden loss of visual acuity and a quadrant visual field defect connected to a physiological blind spot. However, compressive optic neuropathy, demyelinating disease and hereditary disorders must be excluded. 1, diagnosis of anterior segment ischemic optic neuropathy ① sudden loss of visual acuity, typical visual field defect; ② headache, eye scar, especially due to temporal arteritis; ③ there are triggers such as mood swings, nervousness, trauma, etc.; ④ the optic disc is gray-white edema, but no congestion; ⑤ fundus fluorescence angiography shows low fluorescence or slow or no fluorescence filling of the optic disc; ⑤ the wave amplitude value of the three indices of ocular hemogram, blood perfusion (6) Raynaud’s phenomenon in the hands and feet; (7) Significantly lower IOP recovery rate in the ocular compression test; (8) Excluding compression optic neuropathy, demyelinating disease and hereditary disorders, etc. 2, posterior segment ischemic optic neuropathy diagnosis ① sudden loss of visual acuity with visual field defects; ② no headache or eye pain; ③ normal fundus or slightly pale optic disc nasal side with clear border; ④ age older than 40 years, often with hypertension, hypotension, arteriosclerosis or changes in blood composition; younger than 40 years, mostly with Raynaud phenomenon or history of trauma or panic, etc. It is often not easy to diagnose posterior segment ischemic optic neuropathy clinically, and it is difficult to distinguish it from optic nerve papillitis. It is believed that abnormal ocular hemogram or cranial CT confirmed with cerebral infarct area can be used as a reference for diagnosis.