Stroke related eye conditions
Discover how a stroke could affect your sight and the support you could get to recover from your stroke
What is a stroke?
Stroke is the most common cause of adult disability. Every year an estimated 150 000 people in the UK suffer from a stroke. You are more likely to suffer a stroke if you are over the age of 65, but it can occur in all age groups.
Strokes occur when a part of your brain is starved of oxygen. Oxygen is found in your blood and travels throughout all parts of the body including the brain. Blood travels around your body through blood vessels which include arteries, veins and capillaries. The two common causes of stroke are blood clots and bleeding. A blood clot prevents oxygen from being delivered to a part of your brain. Bleeding can occur where a part of your blood vessel wall is weakened causing it to burst and bleed into the brain.
The effects of a stroke are dependent on what part of your brain was affected or starved of oxygen. Every stroke is different and the symptoms and degree of damage are very individual. Some people are mildly affected by the stroke for a short time while others may suffer long term disabilities from the stroke. Some of the common effects of stroke include difficulty or problems with walking, language or speech, mental processes, swallowing, paralysis and eyesight.
As seeing involves not only your eyes but the brain as well, stroke related vision problems can be very complex to understand and treat.
How we see
Your eye is shaped like a round ball. At the front of your eye is a clear tissue called the cornea, it allows light to enter the eye. Light is focused through your pupil which is a hole in the centre of your iris, the coloured part of your eye. Behind the iris is your lens, this also focuses the light coming through the cornea. Both the cornea and the lens focus the light coming into your eye onto an area of your retina.
The space inside your eye is full of a jelly like substance called the vitreous. Your vitreous is clear and takes up the space from behind your lens to your retina.
Your retina is made up of a number of layers but the most important for vision is the layer made up of cells called photoreceptors. Photoreceptors are cells which are sensitive to light. There are two main types of photoreceptors, one type called cone cells and another called rod cells. Cone cells are found in higher numbers around the central part of your retina. This area is also called the macula. Rod cells are found in higher numbers towards the outer edge of your retina.
Cone cells are better at seeing detail, colour and when there is bright light. This means that the macula area of the retina is the part of the retina used when you are looking directly at something, when you are reading or looking at a computer. It responds better to bright light and to seeing colour than the rest of your retina.
Rod cells aren't so good at seeing detail but they are better at seeing in dim light. They are also good at seeing things that are moving. They don't see colour as well as the cone cells, but because there are more of them around the edge of your retina they provide you with your wide field of vision. They help a lot when you are moving around and help you to avoid anything that may be in your way.
Underneath your retina is a layer of blood vessels which help to keep the retina healthy.
To the side of your macula is an area called the optic disc, this is where the optic nerve leaves the eye. The optic nerve connects the eye to the brain.
When light enters your eye it is focused first by the cornea, and then more accurately by the lens, so that it reaches the retina properly. The focussing that the cornea and lens do help to make your vision clear and sharp. When the light reaches the retina the photoreceptors react to the light reaching them by sending a small electrical charge through the optic nerve to the brain. The photoreceptors react differently to different light levels or lighting conditions and this changes the nature of the electrical signals that are sent through the optic nerve. When the parts of your brain that deal with vision receive these electrical signals they make sense of them and this provides you with the pictures that we call sight. All this happens so quickly it is almost instant.
How can a stroke affect vision?
Visual problems are more common when you suffer from a stroke affecting the right side of your brain. The damage the stroke does in your brain impacts the visual pathways of your eye which can result in visual field loss, blurry vision, double vision and moving images. When stroke affects the areas of your brain that process information you see, it can cause visual neglect as well as difficulties with judging depth and movement. In a few cases, visual problems caused by stroke can improve on their own with time.
Some of the vision problems that can occur as a result of a stroke include loss of part of vision or loss of visual field. Visual field is the term used to describe the whole of your vision, from the centre to the periphery. It refers to everything you can see in the periphery of your vision as well as looking directly at something (central vision). Strokes can cause whole sections of your visual field to be missing.
Other visual problems that can occur as a result of stroke include eye muscle and nerve problems which can result in double vision and moving images as well as other effects such as sensitivity to light.
There are various techniques that can be used to try to help or compensate for the various visual effects of stroke. These include glasses, prisms, patching, magnifiers and scanning information to name a few. There has also been some research into computer based rehab programs which may help improve a person's ability to scan when they have field loss.
Usually people who have had a stroke benefit from rehabilitation and that also applies with vision related problems. Orthoptists and Low Vision Specialists can assess and work with people with visual training with or without optical aids; the stroke team, GP or Ophthalmologist can refer people for an orthoptic assessment and/or to the Low Vision Clinic.
Some people may see some improvement in their vision up to four months following a stroke. Again, this is highly dependent on where the damage in your brain has happened as well as the type of stroke suffered and other existing health problems.
Unfortunately for many people, especially those with loss of visual field, sight loss may be permanent.
This type of field loss refers to not being able to see to either the left or right from the centre of your field of vision. People who suffer from a stroke to one side of their brain may develop field loss to the opposite side. The extent of field loss can vary and is directly related to the area of your brain that has been affected by the stroke. Often people may lose half of their visual field meaning they can only see with either the right or left half of each eye; this is called hemianopia.
Hemianopia is a loss of one half of the visual field. It can occur in the right half of each eye called right homonymous hemianopia or in the left visual field referred to as left homonymous hemianopia. The image below right demonstrates left homonymous hemianopia.
The extent of vision loss can vary from slight to severe. Sometimes with hemianopia you may not be aware that you are not able to see from a part of your visual field. You can be taught scanning techniques (eye movement patterns) in the direction of the hemianopia in order to compensate.
Reading can also be a very frustrating experience with hemianopia. If you have right hemianopia, then you will miss the end of words or end of the line. Missing the end of words will result in changing the meaning of words and sentences. Sometimes using a marker at the end of the sentence or a post it note to indicate where the end of the line is can be helpful. A typoscope (a piece of card with a piece cut out) can help. If you have left hemianopia then you may have difficulty finding the beginning of the sentence and finding the next line of text. Once again, using a post it note or ruler to mark the beginning of the text and underneath text can be helpful. It may also helpful to tilt the text and read it vertically.
Optical aids may be used to help increase your field of view and must be fitted by an eye care professional. This may be in the form of prisms which can either be temporary or permanent and applied on the affected side. A prism is a special, transparent, plastic sheet which can be customised to fit any pair of glasses. Prisms do not change the focus or prescription of the lens, but can shift an image either to the right, left, above or below or diagonally as needed. Initially, temporary prisms will be applied to spectacles to ensure correct positioning and during visual training. These prisms are stuck on the back surface of spectacles and can easily peel off if not required. Permanent prisms are mounted into the spectacle frame - into the lens itself. Training with prisms can involve scanning and safety issues while you are in a sitting or standing position and progressing to walking. With the appropriate training, prisms may help you with field loss in all areas of day to day living including navigating around obstacles better while walking.
Other optical aids that may be used are small mirrors attached to spectacles (hemianopic spectacles) that can be adjusted by the wearer. Inverted telescopes which require good central visual acuity can increase visual field.
Eye muscle and nerve problems
A stroke may lead to problems with eye movements which result in both eyes not working together as a pair. This can make it difficult to focus on specific things because of blurred vision as well as diplopia or double vision which impacts on reading, walking and performing everyday activities. People may also experience problems with their fast (saccades) or slow (pursuit) eye movements which make it very difficult for the person to focus visually. In addition, their eyes may wobble (nystagmus) or they may not be able to move both eyes together in a particular direction (gaze palsy). However, recognising this problem can help the person affected by stroke and carers to understand what is going on.
Treatment can involve prisms, exercises and occlusion. Prisms may not only be useful for increasing the field of view, but can help eliminate double vision. Occluding or patching one eye is another effective solution for double vision; however, this method will result in the person having monocular vision (having vision in one eye only). Being monocular can also cause problems such as reduced depth perception (judging how high a step is or how far away something is) and mobility issues due to reduced field of vision. Occlusion does not have to cover the entire lens. Sometimes covering only a part of the lens in the line of sight that is causing the double vision can be done. This form of patching will not result in the person being monocular and therefore may not encounter as many problems with regards to navigation and mobility.
Visual neglect is more common in people who suffered from a stroke in the right side of the brain affecting the left side of the body. Unfortunately, a person with both visual field loss and neglect are less likely to respond to scanning techniques or compensate for the defect. If you are suffering from neglect then you may ignore food on one half of your plate, avoid shaving or applying make-up to one side of your face as well as being unaware of objects and people that are on your affected side which can cause you to ignore or bump into objects that are on that side of you. Treatment for neglect can include prisms or occlusion but most often you are advised on scanning and awareness strategies to cope with the neglect.
Often a person may be able to read text readily, but are unable to make sense of the text. They may attribute this to not being able to see the text properly when it is actually due to processing the information that they have read.
Other problems which can affect vision if you had a stroke include sensitivity to light, dry eye and visual balance disorders.
Another common effect of stroke related vision problems is an increased sensitivity to light. The brain seems to have difficulty adjusting to different levels of light. Tinted glasses or sunglasses may be helpful in alleviating the discomfort you experience.
Another problem reported following stroke is dry eye. The rate of blinking may slow following a stroke and/or you may not be able to close your eyelids completely - partial blink which will cause a part of your cornea to dry resulting in your eye feeling uncomfortable. Artificial tears and reminding yourself to try to blink completely and often may be a possible solution for dry eyes.
Sources of help
Orthoptists play an essential role in assessing and managing many of the visual problems that may result of stroke. Visual training with or without optical aids can be led by orthoptists as well as professionals in Low Vision and Optometrists. In addition, doctors, physiotherapists, speech therapists, rehab workers, nurses and occupational therapists all play a major role in the rehabilitation and recovery process of people who have had a stroke. If you experience any visual difficulties following a stroke, it is important that you have your eyes examined by eye care specialists.
Being diagnosed with an eye condition can be very upsetting. You may find that you are worried about the future and how you will manage with a change in your vision. All these feelings are natural.
Some people may want to talk over some of these feelings with someone outside their circle of friends or family. RNIB can help, with our telephone Helpline and our emotional support service. Your GP or social worker may also be able to help you find a counsellor if you think this would help you.
Sometimes it can help to talk about your feelings or share your experience with people who may have had similar experiences.
Help to see things better
Ask your ophthalmologist, optometrist or GP about low vision aids, like a magnifier, and ask for a referral to your local low vision service. You should also ask whether you are eligible to register as sight impaired (partially sighted) or severely sight impaired (blind). Registration can act as your passport to expert help and sometimes to financial concessions. Even if you aren’t registered a lot of this support is still available to you.
Local social services should also be able to offer you information on staying safe in your home and getting out and about safely. They should also be able to offer you some practical mobility training to give you more confidence when you are out.
Our Helpline can also give you information about the low vision services available, and our website offers lots of practical information about adapting to changes in your vision and products that make everyday tasks easier.
The Stroke Association, serving the whole UK, funds research and provides a growing network of support services. Its Stroke Information Service and Helpline offers information for individuals, their carers, professionals in the field and the general public and provides details of services and stroke groups nationwide.
Chest, Heart and Stroke Scotland offer health advice, general information and a 'listening ear'.
The British and Irish Orthoptic Society provides information on the eye problems that occur following acquired brain injury. They have a stroke-specialist interest group and actively support research on visual impairment following stroke.
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Our guide to “Making the most of your sight” offers ideas for people with sight problems on making life easier and ways of getting the most out of life. This information is also available through the RNIB Helpline.
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