One eye suddenly blurred to see, like a layer of fog may be keratitis, vitreous clouding caused. 1. Keratitis: Keratitis leads to fog in front of the eyes, mainly because the patient overuse of the eyes, the body is more tired, often stay up late and other factors. At this time the patient will also be accompanied by obvious photophobia, tearing performance. 2. Vitreous clouding: Vitreous clouding causes one eye to be blurry and hard to see, like a layer of fog may be caused by the aging of the vitreous body. After the appearance of vitreous clouding, the patient will feel black silk, black spots, black bars appear. Patients should go to the hospital to confirm the diagnosis of the disease, and according to the results of the diagnosis to treat the symptoms.