A stroke can affect your vision in several different ways. If you have vision loss after a stroke, it can make a lot of daily activities difficult, from getting around in and outside the home, to reading, shopping and watching television. About two thirds of people have vision problems after a stroke.
How does a stroke impact vision?
From John Hopkins:
“Vision is dependent on two factors: having a healthy eye to receive the visual information and having healthy visual processing centers in the brain to interpret and process the information. Visual processing occurs in the occipital lobe as well as the temporal and parietal lobes. The effect of stroke on vision loss is variable and often depends on the location and extent of the brain injury.
The occipital lobe processes what we think of as “vision” in terms of the visual image, but the temporal and parietal lobes are essential for visual-spatial awareness, object identification and categorization as well as facial recognition. In general, patients who have strokes or other brain injuries that affect the vision centers on the right side of the brain will have vision loss to the left (in both eyes). Patients who have strokes that affect the vision centers in the left side of the brain will have vision loss to the right (in both eyes).”
Like the other effects of stroke, vision problems can improve over time, as the brain recovers. How you are affected depends on exactly where the stroke occurred in your brain. There are four main areas of visual problems, and you can experience one or more:
- visual field loss
- eye movement problems
- visual processing problems
- other sight problems such as dry eyes & light sensitivity
Symptoms of Visual Field Loss
Visual field loss means that you are unable to see a section of your field of vision, usually because the vision areas of your brain have been damaged by the stroke. The eyes themselves work normally, but the brain can’t process the images from one area of vision. Where the visual field loss happens depends on where the stroke occurred in your brain. It almost always affects the same side of the visual field in both eyes (this is called ‘homonymous’ visual field loss). How much visual field is lost varies between people. The most common type is homonymous hemianopia, which means losing the left or right visual field of both eyes. A less common type is scotoma, when there is a small patch of vision loss, often near the center of vision. Often people think that the vision in one eye has been affected, but it is actually one side of the visual field of both eyes. If just one eye is affected, often with central vision loss, it may be due to damage to the blood supply to the eye itself.
How do you know if you have visual field loss? You may not be aware of the missing area of vision. People with visual field loss often have difficulty reading and may bump into things on the affected side. You might only notice the field loss if you look in a mirror and can only see one side of your face. When reading, it can be difficult to locate the start of a line if you have left-sided field loss. If you have right-sided field loss, it’s harder to see ahead along the line of text. It can be difficult to get around, particularly in unfamiliar or crowded places.
Sometimes people with visual field loss see things that aren’t there in their blind area, known as visual hallucinations. This might be the only time that someone notices the area of visual field loss. Medication can help some people, and reassurance or self-help strategies can assist a person living with the condition.
Occasionally, a loss of central vision is due to a type of stroke affecting the retina, the light-sensitive area of nerves at the back of the eye. This is called a retinal vessel occlusion. It happens when there is a blockage in one of the blood vessels to your eye. The main sign of a blockage in a retinal artery (the vessel carrying blood to the retina) is sudden loss of sight, but you may be aware of some brief periods of sight loss before having permanent vision loss. It’s possible to treat a blockage in a retinal artery if you are seen at a hospital within four hours. However, the retina is very sensitive to loss of blood supply, and it may not be possible to avoid permanent sight loss. If you notice any sudden loss of vision, you should visit your local hospital emergency department straight away.
Symptoms of eye movement problems
A stroke can lead to a variety of problems with the fine nerve control that is needed to move your eyes. We have listed the main ones below.
Impaired eye movements: These may affect your eyes’ ability to move from looking at one object to another or to follow a moving object, like someone walking past. These problems can make reading more difficult and can also affect your general mobility. For example, if you are unable to look around quickly, walking outside is likely to be more challenging.
Inability to move both eyes together: If the nerve control to your eye muscles is affected, one of your eyes may not move correctly. This may cause you to have blurred vision or double vision (diplopia). This is sometimes called a squint or strabismus.
Eyes move constantly or wobble: This can make it hard to focus on objects, or cause double vision. This condition is called nystagmus.
Impaired depth perception and difficulty locating objects: For example, when making a cup of tea, you may misjudge the position of the cup, and pour water over its edge rather than into it.
Symptoms of visual processing problems
Some vision problems after stroke are due to the brain having difficulty processing the information received from the eyes and other senses. This can happen in many ways, for example difficulty recognizing objects or people by sight, or recognizing colors. It can cause difficulty when you try to reach for objects or make it harder to see more than one object at the same time.
Visual neglect: The commonest type of visual processing problem is visual neglect, which means that you are unaware of your surroundings to one side. You may not realize that you are missing things around you. For example, you may be unaware of objects and people on your affected side, and may ignore people or bump into things without realizing they are there. Visual neglect can reduce your ability to look, listen or make movements towards part of your environment. Neglect is more common in people who have had a stroke on the right side of the brain, which affects their awareness of the left side. The person is not aware that they are missing part of their vision. When neglect is severe it may be impossible to draw someone’s attention around to their affected side. Visual field loss and neglect can occur together, which can make it hard to use strategies like visual scanning or patches.
Seeking help from an eye specialist
The goal of vision rehabilitation in patients with stroke is to maximize visual function whether the goals are reading, mobility, or other activities of daily living. As stroke can often affect the processing of information, the cognitive and psychological aspects of a patient are commonly assessed and integrated into rehabilitation. In the Vision Rehabilitation Service, we perform functional visual field assessments and provide patients with education regarding the visual field loss as well as visual processing deficits. In addition, we evaluate prism lenses that can expand the visual field and improve awareness into the missing area of vision.
After a stroke or brain injury, the changes that a patient experiences can be permanent or there can be improvement over time. Patients can be evaluated immediately after the injury and we will continue to follow the patient closely to monitor for improvement and to continue to develop strategies to allow the patient to return to work, independent living, or to achieve their other goals.