Vision loss is the most common symptom of ophthalmology, also known as hazy vision and blurred vision, which seems simple but contains a lot of information. It can be divided into sudden vision loss and progressive vision loss according to how quickly the vision loss progresses. Sudden vision loss can develop very quickly and can lead to blindness in seconds or days, which is an ophthalmic emergency and requires immediate medical attention. For example, “central retinal artery blockage” can cause blindness within seconds; “vitreous hemorrhage” can cause blindness within seconds to minutes; “optic neuritis” can cause blindness within hours to days. Progressive vision loss can occur over months to years, such as cataracts and chronic glaucoma. According to the extent of vision loss, it can be divided into distance vision loss and near vision loss. Farsight loss is common in myopia and aphakia, while near vision loss is common in hyperopia, presbyopia, and post-cataract surgery. According to the duration of vision loss, it can be divided into transient vision loss and recurrent vision loss. Transient vision loss only lasts for a few seconds to a few minutes and is commonly associated with postural hypotension and hypoglycemia; recurrent vision loss is a recurrent episode of transient vision loss and is commonly associated with ischemic optic neuropathy and cervical spondylosis.