1. WHAT IS VISUAL FIELD LOSS?
Visual field is a term used to describe the whole of what you see when you are looking straight ahead. It includes both your peripheral and central vision. Each eye has its own field of vision. The fields of vision of either eye overlap so some objects are seen by both eyes. Objects to the extreme right or left are only seen by one eye.
Visual field loss is when you have lost an area of vision in your visual field. It may be central and/or peripheral. Visual field loss following stroke or head injury usually affects both eyes.
Usually the part of your vision lost is to the same side as any weakness in your face, arms or legs. Strokes which only affect the very back of your brain may cause visual field loss without any other problems. There are different types of visual field loss. The most common visual field loss following a stroke is a homonymous hemianopia. Hemianopia means loss of half of your vision. In other words the right half or the left half of your vision is missing from each eye.
Other types of visual field loss seen following a stroke or head injury are:
■ loss of quarter of the visual field (quadrantanopia)
■ loss of central vision (low vision)
■ random areas of visual loss (random scotomas).
2. HOW CAN I TELL IF I HAVE VISUAL FIELD LOSS?
If you have visual field loss you may:
■ notice that you cannot see objects on one side i.e. you have a blind side
■ some people feel they have lost the vision in one eye i.e. if they have lost their vision to the right they may describe it as having lost the vision in the right eye
■ bump into objects on your blind side
■ easily trip and fall over objects in your blind field
■ find crowded areas more difficult as people and objects suddenly appear in front of you from your blind side
■ experience difficulties with reading and writing. If you have a left sided field loss it is difficult to find the start of the line. In right-sided field loss, reading may be more difficult because you cannot see ahead along a line of text and you can easily lose your place.
3. HOW WILL VISUAL FIELD LOSS AFFECT SOMEONE FOLLOWING A STROKE?
■ People with visual field loss may be disorientated and easily alarmed when objects suddenly appear from their blind side.
■ They have an increased risk of trips and falls.
■ Visual field loss will affect their general mobility and independence.
■ can suffer depression and impaired quality of life.
■ If the visual field loss is associated with visual inattention they may have no awareness that their vision is defective (see leaflet on Visual Inattention following Stroke or Head Injury).
■ They may have visual hallucinations related to their visual field loss (see leaflet on Charles Bonnet syndrome).
■ They will not be able to drive and should notify the DVLA.
4. CAN VISUAL FIELD LOSS RECOVER AND HOW LONG WILL IT TAKE?
Recovery depends on the area of the brain affected and how much damage has been done. Some visual field loss can improve by itself. Improvement has been reported in about 50% of patients with visual field loss following stroke. Recovery is usually seen within the first 3-6 months if it is going to occur.
5. ARE THERE ANY TESTS NEEDED TO CONFIRM THE DIAGNOSIS?
Initially your visual field loss will be detected by a simple bedside test. This is known as a confrontation visual field test. More formal testing of your visual field is done on a machine called a perimeter. If you have had your eyes tested by an Optician you may already have had one of these tests. It is not painful but does require a bit of patience and concentration.
6. CAN VISUAL FIELD LOSS BE CURED?
Visual field loss cannot be cured if it does not spontaneously recover. There are a number of strategies that may be used to allow the patient to adapt to their visual loss. These aim at improving awareness of the visual field loss.
7. WHAT DOES THE TREATMENT FOR VISUAL FIELD LOSS INVOLVE?
Most treatment for visual field loss involves targeted advice for individual patients. None of the treatment options below will permanently cure the visual field loss but may help faster adjustment to the loss.
■ Visual search strategies help to improve awareness of your blind side and help your ability to scan into the blind field. These include increasing head movements and fast eye scanning movements into the blind area.
■ Reading can be helped by using a variety of methods e.g. line guides, typoscopes or magnifiers.
■ Prisms (Pelli prisms) can be used to temporarily to expand your field of vision. They work by displacing images from your blind side onto your seeing side.
■ Visual restorative treatment is a computer based treatment that stimulates the blind field. It has been reported to improve navigation skills, reading ability and visual sensitivity. This treatment is not available on the NHS.
Your Orthoptist will discuss with you the best strategies to use and how to go about doing them.
8. WHAT CAN BE DONE AT HOME TO HELP SOMEONE WITH VISUAL FIELD LOSS?
A number of things can be done to help people with visual field loss. Some methods make the person more aware of their affected side and attend to it better and others are designed to make the best use of the seeing side. For example:
■ encourage visitors to sit on their unaffected side
■ put important things on their seeing side i.e. cup of tea so they can see it easily
■ put a line or tape down the left hand side of books or newspapers so the person knows where the line starts.
9. CAN SOMEONE WITH VISUAL FIELD LOSS DRIVE?
If someone has a hemianopia or visual field loss that affects their central vision, the DVLA states that they are not normally accepted as safe for driving. Persons may be eligible to reapply on an individual basis as exceptional cases subject to strict criteria. These include a stable visual field defect for at least 12 months, absence of a progressive condition and full functional adaptation to the defect. A specialist driving assessment may be undertaken if reapplication is accepted by the DVLA. If in any doubt consult the DVLA website direct for the latest information www.dft.gov.uk
10. WHERE CAN I FIND MORE INFORMATION ABOUT VISUAL FIELD LOSS?
If you would like to know more about visual inattention or have any questions or concerns, please contact the British and Irish Orthoptic Society at:
British and Irish Orthoptic Society
62 Wilson Street, London EC2A 2BU
Tel: 01353 665541
Website: www.orthoptics.org.uk
Email: bios@orthoptics.org.uk
Additional help and advice is also available from:
The Stroke Association
Stroke House, 240 City Road, London EC1V 2PR
Tel: 020 7566 0300
Website: www.stroke.org.uk
Headway – the brain injury association
Bradbury House, 190 Bagnall Road, Old Basford,
Nottingham NG6 8SF
Helpline: 0808 800 2244
Email: helpline@headway.org.uk
Website: www.headway.org.uk
Royal National Institute for the Blind (RNIB)
105 Judd Street, London WC1H 9NE
Tel: 0845 766 9999
020 7388 2525
Website: www.rnib.org.uk