Sudden vision loss in one eye can be caused by many eye diseases, such as foreign body or inflammation of the cornea, inflammation of the iris, acute attack of glaucoma, cataract, etc., while painless monocular vision loss without traumatic factors is usually a manifestation of fundus diseases (retina, choroid, optic nerve, etc.), such as vitreous hemosiderosis, optic neuritis, anterior ischemic optic neuropathy, retinal detachment, etc. Only these types of diseases can cause a dramatic loss of vision in a short period of time. Therefore, it is important to go to the hospital for detailed vision and fundus examination as soon as possible after the occurrence of this condition, and only when the specific cause of the disease is clear can active treatment be carried out. In the case of vitreous hemorrhage, it is usually considered to be caused by retinal diseases, such as retinal vein blockage or eye trauma, which usually does not require special treatment in the early stage and it is recommended to avoid strenuous activities and wait for the blood to absorb on its own. If it is not absorbed at a later stage, surgery may be considered. If the disease is optic nerve disease, such as optic neuritis or ischemic optic neuropathy, it needs active anti-inflammatory treatment. Therefore, it is important to pay attention to the sudden blurred vision in one eye, and early consultation is needed to check the specific cause for early treatment.