Title: Vision Loss, Sudden - Eye Disorders - Merck Manuals Consumer Version
Headings: Vision Loss, Sudden
Vision Loss, Sudden
An Inside Look at the Eye
Causes of Sudden Vision Loss
When the Visual Pathways Are Damaged
Common causes
Less common causes
How and Why Blindness Develops
Table
Evaluation of Sudden Vision Loss
When to see a doctor
What the doctor does
Testing
Treatment of Sudden Vision Loss
Spotlight on Aging: Vision Loss in Older People
Key Points about Sudden Vision Loss
Others also read
Also of Interest
Merck and the Merck Manuals

Content: Common causes
The most common causes of sudden, painless loss of vision are
Blockage of a major artery of the retina ( central retinal artery occlusion)
Blockage of an artery to the optic nerve ( ischemic optic neuropathy)
Blockage of a major vein in the retina ( central retinal vein occlusion)
Blood in the jellylike vitreous humor near the back of the eye (vitreous hemorrhage)
Eye injury
Sudden retinal artery blockage can result from a blood clot or small piece of atherosclerotic material that breaks off and travels into the artery. The artery to the optic nerve can be blocked in the same ways and can also be blocked by inflammation (such as may occur with giant cell [temporal] arteritis). A blood clot can form in the retinal vein and block it, particularly in older people with high blood pressure or diabetes. People with diabetes are also at risk of bleeding into the vitreous humor. Sometimes what seems like a sudden start of symptoms may instead be sudden recognition. For example, a person with long-standing reduced vision in one eye (possibly caused by a dense cataract) may suddenly become aware of the reduced vision in the affected eye after covering the unaffected eye. Less common causes
Less common causes of sudden loss of vision (see table Sudden Loss of Vision) include stroke or transient ischemic attack (TIA), acute glaucoma, retinal detachment, inflammation of the structures in the front of the eye between the cornea and the lens (anterior uveitis, sometimes called iritis), certain infections of the retina, and bleeding within the retina as a complication of age-related macular degeneration. How and Why Blindness Develops
Anything that blocks the passage of light from the environment to the back of the eye or disrupts the transmission of nerve impulses from the back of the eye to the brain will interfere with vision. In the United States, legal blindness is defined as a visual acuity of 20/200 or worse in the better eye, even after correction with eyeglasses or contact lenses, or a visual field restricted to less than 20° in the better eye. Many people who are considered legally blind can distinguish shapes and shadows but not normal detail.