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Vision Loss, Sudden
Loss of vision is considered sudden if it develops within a few minutes to a couple of days. It may affect one or both eyes and all or part of a field of vision. Loss of only a small part of the field of vision (for example, as a result of a small retinal detachment) may seem like blurred vision. Other symptoms, for example eye pain, may occur depending on the cause of vision loss.
Sudden loss of vision has three general causes:
Light must travel through several transparent structures before it can be sensed by the retina. First, light passes through the cornea (the clear layer in front of the iris and pupil), then the lens, and then the vitreous humor (the jellylike substance that fills the eyeball). Anything that blocks light from passing through these structures, for example, a corneal ulcer or bleeding into the vitreous humor, can cause loss of vision.
Most of the disorders that cause total loss of vision when they affect the entire eye may cause only partial vision loss when they affect only part of the eye.
When the Visual Pathways Are Damaged
The most common causes of sudden 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)
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 of sudden loss of vision (see Table: Some Causes and Features of 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.
Sudden loss of vision is an emergency. Most causes are serious.
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause and the tests that may need to be done (see Table: Some Causes and Features of Sudden Loss of Vision).
Doctors ask the person to describe when loss of vision occurred, how long it has been present, and whether if has progressed. People are asked whether loss affects one or both eyes and whether loss is total or affects only a specific part of the field of vision. Doctors also ask about other vision symptoms such as floaters, flashing lights, halos around lights, distorted color vision, jagged or mosaic patterns, or eye pain. Doctors ask about symptoms that are not related to the eyes and risk factors for disorders that may cause eye problems.
The physical examination concentrates primarily on the eyes, but doctors may also do a general physical examination, including, for example, examination of the skin and the nervous system.
For the eye examination, doctors first carefully check sharpness of vision (visual acuity), usually by having the person read letters on a chart, first while one eye is covered and then with both uncovered. Doctors check how the pupils narrow (constrict) in response to light and how well the eyes can follow a moving object. Color vision may be tested. Doctors examine the eyes and eyelids using a slit lamp (an instrument that enables a doctor to examine the eye under high magnification—see Figure: What Is a Slit Lamp?) and measure pressure in the eye. Ophthalmologists, after instilling drops that dilate the pupils, examine the retina thoroughly with a slit lamp or light that is shone from a head lamp through a hand-held instrument.
Some Causes and Features of Sudden Loss of Vision
The presence or absence of pain helps narrow the list of possible causes considerably (see Table: Some Causes and Features of Sudden Loss of Vision). If vision returns quickly on its own, transient ischemic attack and ocular migraine (see Some Causes and Features of Sudden Loss of Vision) are among the likely causes.
Often findings during the eye examination provide enough information for doctors to diagnose the cause of loss of vision. Sometimes, however, testing is needed depending on what disorders are suspected (see Some Causes and Features of Sudden Loss of Vision). The following tests are of particular importance:
Ultrasonography is done to view the retina if the retina is not clearly visible during an ophthalmoscopic examination.
Gadolinium-enhanced MRI is done for some people with eye pain and certain other symptoms and when optic nerve swelling is seen during the eye examination.
Erythrocyte sedimentation rate (ESR) and C-reactive protein level (blood tests that indirectly measure inflammation in the body) are done and the number of platelets in the blood (platelet count) are measured, particularly in people over age 50 or who have headache.
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