Hemianopia is a loss of half a person’s peripheral vision. This means a person loses the right half or left half of vision in each eye. Hemianopia can occur from injury to the brain, such as a stroke.
Vision relies on the ability of the eyes to take in visual information, and the brain to process this information and interpret it correctly.
A stroke can damage areas of the brain that allow vision. This can cause changes to vision or loss of visual field.
This article looks at what hemianopia is, how a stroke may cause it, symptoms, diagnosis, and treatments to manage the condition.
Hemianopia is the loss of half a person’s peripheral vision. Doctors may also refer to hemianopia as homonymous hemianopsia.
Visual field is the term for the complete area that people see when they look straight ahead. The visual field includes central and peripheral vision.
With hemianopia, a person’s visual field is vertically cut in half.
A stroke or brain injury can affect visual field, and usually causes visual field loss in both eyes. The vision loss is due to injury in the brain, rather than any problems with the eyes.
Hemianopia is the most common type of visual field loss following a stroke.
In adults, ischemic stroke and hemorrhagic strokes can cause hemianopia. In children,
If a stroke causes damage to these areas of the brain, it can affect vision and cause vision loss such as hemianopia.
People with hemianopia will be unable to see the right or left side of their vision in each eye. If people move their head to the left or right, they will be able to see what was previously in a blind spot.
Compared to a full field of vision, people will only see half the field of vision, as though the rest does not exist.
People may also:
- be unable to see objects to one side of them
- bump into objects outside their field of vision
- easily trip or fall over objects or areas they are unable to see
- have difficulty moving in crowded areas, as people may seem to appear suddenly from the side of vision loss
- have difficulty reading and writing, such as following a line of text or finding the start of a line
Depending on whether hemianopia affects the right side or left side of each eye, people may find it harder to see objects or areas on the side of their vision loss.
This may cause:
- difficulty crossing the road, which may be dangerous if unable to see oncoming vehicles
- bumping into objects
- an inability to see objects on one side of a table or desk
- an inability to see food on one side of the plate so may leave uneaten
- difficulty reading lines of text
- an increased risk of falls due to vision loss
It may no longer be safe for people with hemianopia to drive, as they may not be able to change lanes safely or see vehicles or objects to one side of them.
People may be able to use a driving simulator with an examiner to test whether they are safe to drive or not.
Treatment of hemianopia focuses on rehabilitation and helping people to adapt to their visual field loss. This may include:
- prism glasses, which help people to transfer the area in their blind spot to within their visual field
- therapies to improve reading, such as saccadic training which teaches people to move their eyes into the area of vision loss
- scanning techniques, which increase head and eye movements to help people scan into their areas of vision loss
- using reading aids, such as colored markers or line guides
- computer programs to help stimulate the blind area of vision
Outlook and recovery for hemianopia may vary for each person, depending on the amount of time between a stroke and diagnosis of hemianopia. It can also depend on the severity of brain damage and which area of the brain it occurred in.
In some cases, hemianopia may improve. The United Kingdom’s National Health Service (NHS) notes around 50% of people with visual field loss may experience an improvement.
If hemianopia does improve, it usually happens in the 3–6 months following the stroke. A person’s ophthalmologist can help track their progress by monitoring their visual field with a test called perimetry or visual field test.
Although less likely, it is still possible that improvements may occur after this time.
A stroke that causes severe damage to the brain may result in poorer outcomes.
There is no cure for hemianopia. However, treatments can help people to adapt to visual field loss and may help with day-to-day living.
To diagnose hemianopia, a healthcare professional will carry out a range of visual field tests, such as:
- confrontation visual field test, in which a health professional will sit in front of the person and hold targets for them to see in their peripheral vision
- perimetry test, in which a person sits in front of a perimeter machine that creates a map of a person’s peripheral vision
To find out the cause of hemianopia, doctors may carry out tests such as MRI scans to check for the location and extent of brain injury.
- managing high blood pressure and cholesterol through a healthy diet, which is low in saturated fats, trans fats, and high in fiber
- achieving and maintaining a healthy weight
- getting regular physical activity
- avoiding smoking
- limiting alcohol
- managing any existing health conditions which can increase the risk of stroke, including high blood pressure, heart disease, and diabetes
- taking any necessary medications as a doctor prescribes
Hemianopia is the loss of half a person’s usual field of vision. People may lose vision on either their right or left half of their vision in each eye.
A stroke can damage areas of the brain that control vision, resulting in vision changes. Hemianopia is the most common loss of vision from a stroke.
Hemianopia can affect day-to-day activities, such as reading, navigating objects, and crossing the road. It may not be safe for people to drive or handle heavy machinery.
Treatments can help people adapt to visual field loss, and may include prism glasses, reading aids, and therapies to adjust eye movements to account for vision loss.