The causes of sudden vision loss include keratitis, glaucoma and fundopathy. 1. Keratitis: Sudden loss of vision may be caused by acute inflammation of the cornea, mostly due to bacterial viruses or other pathogenic microorganisms attacking the cornea, or autoimmune diseases, conjunctivitis, scleritis and so on. All of them may cause patients to have different degrees of sudden vision loss. 2. Glaucoma: During the acute attack of glaucoma, the patient’s vision may suddenly and severely diminish, and may be accompanied by different degrees of eye pain, nausea and vomiting. 3. Fundus lesions: If the patient has problems with the fundus of the eye, such as vascular diseases of the fundus or macular abnormalities, it may lead to a sudden loss of vision. In addition, sudden vision loss may also be caused by high blood pressure or diabetes. It is recommended that the patient should consult a doctor for timely examination and treatment according to the different causes under the guidance of the doctor.