Foggy eyesight, or vision loss (blurred vision). As shown in the picture: How is blurred vision caused? Most blurred vision is caused by eye diseases. There are many common eye diseases that cause blurred vision, and their clinical manifestations and characteristics are different. For example: 1. Common eye diseases that can cause transient blurred vision or even loss of vision (vision can return to normal within a short period of time, usually less than 24 hours) include: optic disc edema (seconds, usually both eyes); transient ischemic attack (minutes, one eye); inadequate blood supply to the basilar artery (both eyes), postural hypotension, psychostimulant blackout, central retinal artery spasm, hysteria, overexertion. Migraine (10-60 min with or without subsequent headache); impending central retinal vein obstruction, sudden change in blood pressure, acute orbital pressure elevation, central nervous system lesions, etc., also occasionally seen in ischemic optic neuropathy and glaucoma, etc. 2. Common eye diseases with sudden vision loss without eye pain include: retinal artery or vein obstruction, ischemic optic neuropathy, vitreous hemorrhage, retinal detachment, optic neuritis (usually accompanied by oculomotor pain), etc. 3. Common eye diseases with gradual vision loss without eye pain include: cataract, refractive error (myopia, hyperopia, astigmatism), primary open-angle glaucoma, chronic retinal diseases (such as age-related macular degeneration, idiopathic macular fissure, diabetic retinopathy, chronic corneal disease), etc. 4. Common eye diseases with sudden vision loss and eye pain include: acute angle-closure glaucoma, uveitis, corneal inflammation, endophthalmitis, ocular trauma, etc. 5. The common eye diseases with decreased vision but normal fundus include: retrobulbar optic neuritis, early optic cone cell degeneration, early optic nerve contusion, poisoning, optic neuropathy due to tumor, total color blindness, amblyopia, hysteria, etc. In addition, blurred vision can occur when ocular complications arise from systemic diseases such as hypertension, renal disease, hematologic disease, diabetes mellitus, and intracranial lesions involving the visual pathway.