Vision problems as a result of strokeGeneral information on Stroke
What is a stroke? Stroke is a cerebro-vascular accident or brain attack. There are two types of stroke: ischaemic – where there is a blockage of blood flow to part of the brain – and haemorrhagic – where there is a bleed in part of the brain.
How common is it? Every year, an estimated 110,000 people in the UK have a first stroke1. Another 30,000 will have a recurrent stroke. Some individuals may have transient signs and symptoms that last less than 24 hours and this is termed a TIA (transient ischaemic attack). It is very important to follow up on such transient problems as TIA is a known precursor to a full stroke.
How common is visual impairment following stroke? Visual impairment is common following stroke and includes problems such as blurred vision, double vision, field of vision loss, wobbling vision and many others. These symptoms can be addressed in a variety of ways such as with targeted treatment, advice, compensatory strategies and so on. This is important as visual impairment impacts on mobility, rehabilitation, driving, reading and general activities of daily living.
More information can be found from this document and by following these links:
STROKE INFORMATION UPDATES May2011.pdf
Stroke Charles Bonnet leaflet Nv 2011.pdf
Stroke Visual Inattention leaflet Nov 2011.pdf
Stroke Visual Fleld Loss leaflet Nov 2011.pdf
This is some information from the RNIB website.
Field loss (Hemianopia)
This type of field loss refers to not being able to see to either to the left or right from the centre of your field of vision. People who suffer from a stroke to one side of the brain may develop field loss to the opposite side. The extent of field loss can vary and is directly related to the area of the 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'.
Left homonymous hemianopia
The extent of vision loss can vary from slight to severe. Some people with hemianopia are aware that they are not able to see from a part of their field and 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 for someone with hemianopia. A person with right hemianopia misses the end of words or end of the line. Missing the end of words will result in changing the meanings 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 for some. A typoscope (a piece of card with a piece cut out) can help. People with left hemianopia 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. People may also benefit from tilting the text and reading it vertically.
Optical aids may be used to help increase a person's field of view and must be fitted by an eye care professional. These 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 the person is in a sitting or standing position and progressing to walking. With the appropriate training, prisms can help people 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 (Diplopia)
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, making 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 their 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, that is vision in one eye only. Monocular vision can itself 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 have as many problems with 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. People suffering from neglect may ignore food on one half of their plate, avoid shaving or applying make-up to one side of their face as well as being unaware of objects and people that are on the affected side resulting in the person ignoring or bumping into objects that are on that side of them. Treatment for neglect can include prisms or occlusion but most often people are advised on scanning and awareness strategies to cope with their neglect.
Often a person may be able to read text readily but be 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 not being able to process the information they have read.
Other vision problems associated with stroke
A 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 reducing the discomfort some people experience.
Another problem which can follow stroke is dry eye. The rate of blinking may slow following a stroke and /or there may be incomplete eye closure with a partial blink which will cause a part of the cornea to dry resulting in the eye feeling uncomfortable. Artificial tears, and reminding the person to try to blink completely and often, may be a possible solution for dry eyes.
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