What is hemianopia?
Hemianopia, or hemianopsia, is a loss of vision or blindness in half the visual field, to either the right or left side, which can occur after stroke, brain injury, or a brain tumour.
Although hemianopia does not affect all of a person’s vision, it can still have a major impact
on their lives and independence. Hemianopia affects things like reading, driving and how people are able to avoid objects as they move around.
The chances of recovery are better if the patient’s hemianopia is caused by inflammation rather than a stroke. While hemianopia can be permanent, some management options can help patients adapt to reduced vision, including strategies to improve navigation and reading ability.
How common is hemianopia in people who have had a stoke?
According to Stroke Association, around 180,000 stroke survivors live with hemianopia.
Patients can spontaneously recover from hemianopia, but only around 15% of stroke survivors will fully recover their vision in the weeks after their stroke.
What are the different types of hemianopia?
Left and right Homonymous hemianopia: Left hemianopia causes a loss of visual field in the left half of each eye. Right hemianopia causes a loss of visual field in the right half of each eye.
Complete and partial Homonymous hemianopia: Complete hemianopia involves all of the visual field from the centre outwards. Partial hemianopia involves only part of the visual field. Some field of vision remains on the affected side.
Heteronymous hemianopia is the loss of half of the visual field on different sides in both eyes. It is separated into two categories:
- bitemporal hemianopia: A loss of visual field in the outer (temporal or lateral) half of both the right and left visual fields.
- binasal hemianopsia: The loss of the visual fields nearest the nose, in the inner half of each eye.
What is quadrantanopia?
Whilst hemianopia involves both the upper and lower parts of the visual field to one side, it is possible to lose only the upper OR lower part of the visual field. This is called quadrantanopia.
There are different types:
- Superior quadrantanopia: A loss of visual field in the upper half of each eye to either the right or left side.
- Inferior quadrantanopia: A loss of visual field in the lower half of each eye to either the right or left side.
What are the symptoms of hemianopia?
The symptoms of hemianopia can range from mild to severe.
Hemianopia can cause individuals, who are unaware of their condition, to believe they have lost vision in one entire eye rather than the actual loss in both eyes.
- Here are other known symptoms:
- distorted or blurry sight
- failing to see from the affected side
- spatial awareness problems
- frequently bumping into objects you cannot see
- your visual sight appears dimmed
- reduced night vision
- visual hallucinations
- reading difficulty
How might hemianopia impact on someone's daily life?
A person with hemianopia may experience a range of problems when carrying out everyday activities such as:
Finding objects: Locating things can be difficult if a person is unable to see properly either to the left or to the right of the centre of their field of vision. It may be useful to reduce the number of objects that are on surfaces at home as clutter can make it more difficult to pick out individual items.
Mobility: Moving through different environments - such as crossing roads, or navigating around crowded places like shopping centres - can be challenging if a person can’t fully see where they’re going. They are also at risk of bumping into objects or tripping over things that they may not have seen.
Reading: People may experience difficulties reading text such as books and magazines - as words and sentences can disappear when in the missing visual field. Rulers and markers can help highlight the beginning and end of sentences and keep the position along a line of text.
What causes hemianopia?
The most common cause of hemianopia is stroke. Around 30% of stroke survivors experience hemianopia.
“Around 30% of stroke survivors experience hemianopia”
However, here are a few other causes:
- Abnormal blood vessels
- Brain injuries
- Brain tumours
- High Pressure in the brain
- Multiple sclerosis
- Neurosurgical procedures
- Shaken Baby Syndrome
What is the leading cause of hemianopia?
The most common cause of hemianopia is stroke, followed by trauma and tumours.
Hemianopia is caused by a lesion in the posterior part of the visual pathway – including optic tract, lateral geniculate body, optic radiations and visual cortex.
How is hemianopia diagnosed?
The most common way to diagnose hemianopia is a visual field exam. This can be done by ‘confrontation’ where the clinician checks the patients responses to arm and finger movement. More accurate assessment is done using ‘perimetry’ tests. The patient will be asked to focus on a target in front while noting lights flashed above, below, left and right of the target. Magnetic resonance imaging (MRI) of the brain can also be used to diagnose the underlying cause of the brain injury leading to hemianopia.
How is hemianopia treated?
First, the cause of hemianopia (e.g. stroke, tumour, head trauma) is treated. In turn, this may help restore some function of the visual pathway within the brain.
People with hemianopia may regain their visual field over time without any treatment. They may still benefit from treatment in the early, non-recovered stages.
But sometimes, a person’s field of vision never resolves. In these cases, there are other things that can be done to help them to make the best use of their remaining sight.
An eye clinician may recommend different strategies to help an individual with hemianopia to cope with their visual problems.
Treatment for hemianopia include the following:
Visual scanning training for hemianopia
Scanning exercises encourage a person to look to their left and right side systematically to help improve their awareness of the visual field loss and remind them to look into their blind side.
For example, they could practice by keeping their head still and moving their eyes around the room to their affected side of vision - or using puzzles and word search games to improve their visual detection and tracking skills.
Reading strategies to treat hemianopia
Using a straight edge under each line or text, or a piece of card with a rectangle cut out, can be helpful by making it easier to focus on a line of text at a time.
Placing a hand or marker on the edge of the page can help make it easier to determine where the page margin is. It may also be helpful to tilt the text at an angle and reading it vertically rather than horizontally.
Visual aids for people with hemianopia
Magnifiers can be helpful when reading as it can be easier to scan larger print than standard size print.
In some circumstances, wearing prismatic correction glasses can help widen a person’s field of view. The prism is worn on the side of the visual field loss, creating a blurred, overlapping image that the person can see on their good side.
This acts as a prompt to look towards the blind side.
Lighting options for people with hemianopia
Taking steps to make sure there is good lighting and, if possible, positioned to the side rather than behind the person (which can cause shadows) can be helpful.
Visual restorative treatment for hemianopia
Different strategies are available that aim to help a person to interpret visual information by building awareness of moving images in their blind field of vision.
In addition, support from friends of family can help. For instance, having a walking partner who can provide guidance when moving around challenging environments.
What research is underway into hemianopia?
Current treatment to help those with hemianopia compensate for their visual field loss is variable and not standardised in the NHS. This is due to uncertainty about what works best and when is the right time to offer treatment.
In a project jointly funded with the Stroke Association, researchers at the University of Liverpool are exploring whether visual scanning training could improve the patient experience, encouraging stroke survivors to scan the ‘blind’ side of their visual field to improve their adaptation to loss of vision on that side.
Researchers are successfully screening and recruiting patients for a study exploring a new approach to 'retrain' the eyes after stroke.
Following a successful pilot, Professor Fiona Rowe and her team are in the process of running a large-scale study using paper-based visual scanning training.
The team hope that this simple, low-tech method will help patients to adapt to hemianopia and be widely transferable and used in different care settings.
Think you have hemianopia? Here's what you can do
If you are experiencing any visual difficulties, it’s important to have your eyes examined by an eye care specialist so you can get an accurate diagnosis. If you have hemianopia, you should receive clear information about your condition and be offered treatment if it is appropriate.
Last updated March 2023
Approved by Professor Fiona Rowe, University of Liverpool