OCULAR SYMPTOMS 

Loss of Vision

Introduction: Loss of vision

A loss of vision can be a frightening experience, and all people with a sudden loss of vision should be seen by an ophthalmologist as an emergencgy. Here, loss of vision refers to a severe blurring of the vision in one or both eyes often to the point that almost no detail can be made out. There may be large blind spots in the vision, or the appearance that something is blocking the vision. With these symptoms, there is almost always a cause for the visual loss other than a simple change in glasses.

Many things that cause blurred vision can also cause a loss of vision, if the condition is severe enough. These conditions are discussed on the Blurred Vision page. Many other eye problems can cause a loss of vision along with other symptoms. Links to Symptom and Diagnosis pages based on these other symptoms are included as well.

Conditions:

For eye anatomy explanations, go to ANATOMY

Amaurosis Fugax

Amaurosis fugax refers to a temporary black-out of vision. This is usually affects one eye, is painless, and is often described like a "shade coming down over the vision" of that eye. The black-out may last minutes, and then the vision returns. The problem can recur in the future, and could affect either eye. Most commonly, this happens in older people with arteriosclerosis and possibly vascular disease, and is due to small clots breaking off of the walls of arteries and then lodging in the vessels of the eye. The clot obstructs the blood flow to the retina, and the vision blacks-out. When the clot breaks up, the blood flow returns, as does the vision. The source of the clot (or embolus) is usually from the carotid arteries leading up the neck to the brain, or from the heart. The embolus may be a cholesterol crystal, a calcium deposit, or a true blood clot. This problem falls into the same category as "transient ischemic attacks" (or TIA's), which may herald a stroke. Vascular evaluation and possibly anticoagulation (use of blood thinners) is indicated for this problem.

Other problems which cause a temporary loss of vision include:

• Obstruction of the vertebral arteries, which course up the back of the neck and supply the visual part of the brain. People which this problem may notice temporary dimming of vision affecting both eyes, and possibly imbalance.
• Increased intra-cranial pressure (the pressure of the fluid around the brain) can cause momentary lapses of vision especially when moving, such as standing from a sitting position. Sometimes even eye movements are enough to induce a temporary loss of vision.
• Retinal migraine is a spasm of the artery leading into the eye which supplies the retina. This spasm can lead to a temporary black-out of vision on one side, and is fairly rare.

Retinal Artery Occlusion

If a clot (embolus) breaks free from the wall of a blood vessel leading up the neck or to the eye, it can lodge in the retinal arteries causing an obstruction of blood flow to the eye, and a loss of vision. In some cases, the clot will rapidly dislodge, and the vision will return (Amaurosis fugax, discussed above). However, if the clot is large it may not dislodge, and the vision remains blacked-out. Usually this is painless, and the loss of vision is severe. If the blood flow to the retina is interrupted for more than 1 1/2 hours (approximately), the vision may not return even if the clot breaks free and the circulation is restored. This condition may indicate risk for cardiac disease, and stroke.

If a person with this condition rapidly seeks the medical help by an ophthalmologist, things may be able to be done to dislodge the clot before permanent damage occurs. No ophthalmologist will turn a patient away with this condition.

Retinal Vein Occlusion

The retinal blood circulation is drained by a single vein, called the central retinal vein. If this vein becomes obstructed, various problems can occur in the eye, depending on the severity of the obstruction. A person with this condition( will notice blurring of vision, dimming of vision, and possibly blind spots and floaters in the vision. It usually starts fairly suddenly, but the vision may worsen over a period of time (hours to days). Rarely does this happen in both eyes at the same time. The problem is usually caused by underlying vascular disease, and sometimes abnormal clotting or blood thickness. It is not caused by clots breaking off of arteries, like an artery obstruction is.

There is no effective treatment to reverse the blockage of the vein, except to treat any underlying medical condition (diabetes, hypertension, increased cholesterol, etc.), and hope that the vein opens back up on its own. About 1/3 of cases will completely resolve with little damage to the vision. About 1/3 stay the same with some loss of vision, and 1/3 of cases worsen and develop more severe loss of vision. The worst cases may need to be treated by a laser to prevent a dangerous form of glaucoma (neovascular glaucoma), but the laser treatment will not help the vision. Studies are being done to evaluate possible medication or laser treatments which may help people with this condition. (For a related topic, see Macular Edema.)

Stroke (Cerebrovascular accident, or CVA)

A stroke is an obstruction of blood flow leading to a part of the brain. If the part of the brain affected serves the vision, there may be a loss of vision with the stroke. If a small area of brain is affected, there may be a blind spot in the vision corresponding to that area. However, with more substantial stroke, an entire side of vision can be lost. The visual part of the brain has a left and right side. The left side serves the right half of the vision from both eyes, and right side serves the left half. Thus if there is a stroke of one side of the brain, the person may lose the corresponding half of vision of both eyes. Most people notice this more from the eye that lost the outside field of vision. (For example, a stroke of the left side of the brain would cause the right half of vision to be lost from both eyes. This would be the inside half of vision of the left eye, and the outside half of vision of the right eye.)

Strokes affecting the visual part of the brain are treated as any stroke of the brain, and usually the problem is evaluated by internal medicine physicians, or neurologists.

Macular Hole

Some people develop a degeneration of the part of the retina that serves the central vision (reading vision), which is called the macula. Unlike macular degeneration, where there is gradual deterioration of the macula possibly associated with hemorrhage under the retina, a macular hole is a sharply outlined loss of retina in the center of the macula. It is not fully understood why this happens. There may be some risk for the second eye being affected as well.

Usually there is a fairly severe loss of reading vision (central vision), with a blind spot appearing centrally. The peripheral vision remains normal. There is a surgical procedure which may help some macular holes to fill back in, with some return of vision.

Retinal Detatchment

Retinal Detachment

A retinal detachment occurs when fluid in the eye gets behind the retina, and lifts it off of the wall of the eye on the inside. Normally the fluid in the eye has no way to get under the retina, but if a tear in the retina occurs, a detachment could follow. A retinal detachment is usually perceived as a dark area encroaching on, or covering, the central vision from the outside. The symptoms may seem to occur suddenly, or may worsen over a short period of time. A retinal detachment including the macula (the central visual part of the retina) will cause a substantial loss of vision. Retinal detachments can be repaired surgically with usually good results, depending on the severity of the detachment, how long it has been present, and if the macula is involved or not.

People who are highly nearsighted may be at increased risk for retinal detachment, as are people who have had eye trauma. There are certain conditions of the retina which lead to detachment in the future, and sometimes these are treated prophylactically. The most common of these is a retinal tear, and symptoms of retina tear usually preceed a detachment (floaters and flashing lights). A person with these symptoms should be examined promptly by an ophthalmologist. (See Retinal Tear for more information.)

Retinal Detatchment

Vitreous Hemorrhage

Bleeding into the eye can cause substantial loss of vision, since the blood clot obstructs light images from reaching the retina. The main cavity of the eye is filled with a gel-like substance called vitreous, and bleeding into this is a "vitreous hemorrhage". Blood becomes trapped in this gel, and does not immediately sink to the bottom of the eye or dissolve.

Thus, symptoms usually include seeing floaters or spots in the vision which increase with time (and possibly flashing lights). With more severe hemorrhages, a dark, reddish blob which seems to move, may cover the vision. Most vitreous hemorrhages will resolve spontaneously with time, although some need to be removed surgically. The most important thing is determining the cause of the hemorrhage. The bleeding can occur with the following conditions, some of which are discussed elsewhere:

Other Conditions causing a loss of vision found on other pages:

Loss of Vision video