Vision loss can be due to a variety of ophthalmic diseases, such as cataracts, refractive error, advanced glaucoma, fundus disease, and optic nerve disease. It may also be a complication of other systemic diseases or a psychogenic visual impairment. (1) Loss of vision lasting from a few seconds to a few minutes: optic papilloedema, retinal artery spasm, transient blackout (transient ischemic attack, often monocular), and vertebrobasilar artery insufficiency (bilateral attacks); (2) Loss of vision lasting from 10 to 60 minutes: migraine (with or without subsequent headache). Loss of vision for more than 24 hours: sudden, painless vision loss is common in conditions such as retinal artery or vein obstruction, ischemic optic neuropathy, vitreous hemorrhage, retinal detachment, optic neuritis (more than 50% with painful eye rotation), central nervous system disease (e.g., stroke), methanol poisoning, ophthalmic artery obstruction (may be associated with abnormal eyelid movement and ptosis), etc. Chronic painless vision loss (weeks, months, or years): common conditions include cataract, refractive error, chronic corneal disease, open-angle glaucoma, chronic closed-angle glaucoma, chronic retinal disease (e.g., age-related macular degeneration, diabetic retinopathy), and optic neuropathy. With ocular painful vision loss: acute closed-angle glaucoma, optic neuritis (painful eye rotation), uveitis, endophthalmitis, corneal edema (cone cornea). Psychogenic disease or hysteria may be considered in the absence of organic ocular pathology. Most of the diseases of ophthalmology can manifest as vision loss, and vision loss should be promptly seen in the hospital for ophthalmic examination to clarify the cause.