Stroke ("Brain Attack") / Visual Field Defects
What Is a Stroke ("Brain Attack")?
Every year, more than half a million people suffer a stroke in this country. The American Heart Association wants people to think of a stroke as a “brain attack” which requires the same degree of emergency response as a heart attack. Because anti-clotting medications can significantly reduce the affects of a stroke if administered within three hours, you should call your doctor or 911 immediately if you experience one or more of the following symptoms:
- Sudden weakness or numbness on one side of the body
- Sudden severe headache
- Sudden loss of vision or double vision
- Dizziness or falling, with no obvious cause
- Difficulty with speech
Strokes are caused by sudden disruptions of the blood supply to the brain. They are usually caused by blockages in the arteries in the brain. In some cases, leaky blood vessels or hemorrhage can also cause a stroke. The disruption in the blood supply cuts off the oxygen supply to parts of the brain, resulting in damaged brain cells.
Before a stroke, there may be a warning sign, such as a brief but temporary loss of vision caused by a mini-stroke. The technical name for a mini-stroke is a transient ischemic attack or TIA. It is possible to prevent a stroke if a TIA is properly diagnosed and treated. Therefore, even a brief or temporary loss of vision should not be ignored. A TIA involving the eye is called Amaurosis Fugax.
A stroke can cause permanent or temporary impairment of movement, speech, communication and thinking. From a vision perspective, a stroke can also have a significant impact on your vision. A stroke in the left side of your brain affects the opposite side of your body. It could cause weakness in your right arm and leg, and the vision on your right side may be affected.
Depending on the location of the stroke in the brain, you may lose the ability to see clearly, your peripheral vision, and your visual perception. The movement of your eye muscles may also be impaired. The vision impairments from a stroke can impact your ability to do everyday activities including reading, watching TV or driving. Wearing glasses may not improve your vision.
The most common vision problem resulting from a stroke is called a homonymous hemianopsia, the physical loss of half your field of vision in each eye. The vision loss would be the inner visual field in one eye and the outer visual field in the other. Often people who experience hemianopsia think that one eye is involved, because they can’t see things on one side. In actuality, they’ve lost half their field of vision in each eye.
Depending on which part of the brain is involved, you would be able to see to one side of a theoretical line drawn down the center of your field of vision, but not to the other. Using the example above, if a stroke has resulted in weakness in your right arm and leg, as well as homonymous hemianopsia, you would be able to see to the left side of your field of vision but not the right.
A visual field loss from a stroke may improve during the first three to six months after a stroke. However, in most cases of hemianopsia, there is no improvement in vision.
Another type of visual field defect that can result from a stroke is called visual neglect or visual imperception. Rather than a physical loss of visual field, visual neglect is a mental or attentional problem. This is an unconscious lack of awareness of part of your field of vision.
Visual neglect can have a significant impact on everyday life. Even though your visual acuity was not affected by the stroke, your brain is unable to process the images on your retina. Therefore, if the left side of your brain was affected by the stroke, you would be unable to see the words on the right side of the page or objects on the right side of a table.
If your stroke occurred on the right side of your brain, you would be more likely to experience both physical loss of visual field and visual neglect.
How Are Visual Field Defects Detected?
If doctors suspect that you have had a stroke, you will undergo a full series of medical and neurological testing. This will likely include a physical examination, complete blood work analysis, along with CT scan. Additional testing may include an MRI and ultrasound. This testing will pinpoint the location of your stroke.
To determine the extent of impact to you vision, the following test would likely be required:
- Visual Field Testing: Measuring the sensitivity of central and peripheral (sideways) vision
- This test is performed in our office with a computerized visual field analyzer
How Are Visual Field Defects Treated?
Unfortunately, there are no medical treatments that will improve vision loss due to a stroke. In some cases, visual field loss due to homonymous hemianopsia may improve on its own. Therefore, learning to compensate for both visual field loss and visual neglect is the focus of treatment following a stroke.
If you suffer vision loss from a stroke, we recommend that you work with a low vision specialist. To deal with visual field loss from hemianopsia, the specialist will utilize tools including scanning techniques and prisms to help you compensate for the diminished vision on one side.
It may also be necessary for you to do exercises to improve the movement of the muscles in your eyes. If you have difficulty reading, particularly if you have visual neglect, the low vision specialist will teach you techniques to help you see the entire word or page that you are reading.
The most important thing to remember is that prompt medical attention, including anti-clotting medication, is the key to minimizing the impact of a stroke. Therefore, at the first sign of symptoms, immediately call your doctor or 911.
Neuro-Ophthalmology Specialist at Kadrmas Eye Care New England
Meet our neuro-ophthalmologist who specializes in the treatment of neurological eye diseases and disorders: