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Information on epilepsy: Photosensitive epilepsy |
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If you have epilepsy you may be able to identify triggers - situations that cause your seizures. Common triggers are stress or tiredness. If seizures are triggered by flashing lights or patterns, this is called photosensitive epilepsy. How common is photosensitive epilepsy?Around one in 131 people have epilepsy and of these people, up to 5% have photosensitive epilepsy. This is when seizures are triggered by certain frequencies of flashing lights or contrasting light and dark patterns such as stripes or checks. Photosensitivity is more common in children and young people and is less commonly diagnosed after the age of 20. How can I tell if I am photosensitive?Many people find this out because they have a seizure when exposed to flashing lights or patterns. A tonic clonic (convulsive) seizure is the most common type of seizure to be brought on by photosensitivity, although this may vary from person to person. If a seizure happens due to photosensitivity, it will normally happen straightaway. Some people with photosensitive epilepsy also have seizures that are not triggered by flashing lights or geometric patterns, while other people may only have seizures due to this trigger. When
an Electroencephalogram (EEG) is carried out, a flashing light test, called
photic stimulation, will often identify if you are photosensitive. The
light test is stopped if it looks like you might have a seizure. What frequency of flashing light is most likely to trigger a seizure?Between five and 30 flashes per second (hertz) are the common frequencies to trigger seizures, but this varies from person to person. While some people are sensitive at higher frequencies than 30 hertz, it is not common to be sensitive below five hertz. What patterns are most likely to trigger a seizure if I am photosensitive?Some people are sensitive to geometric patterns, which have strong contrasts of light and dark eg. stripes or checks. These might be on a TV or computer screen, or something in the natural environment, such as sunlight through trees, or through venetian blinds. Such contrasting patterns are more likely to be a trigger if they are moving, changing direction or flashing, rather than if they are still. Common triggers for people with photosensitive epilepsy include:
What factors can affect photosensitivity?
Can computer screens and computer games trigger photosensitive epilepsy?Most people with photosensitive epilepsy do not have a problem with using modern computer screens, as they usually operate at a very high flicker frequency. Computers with flatscreen monitors, such as laptops, have a liquid crystal display (also called LCD or TFT) that does not flicker. This makes them even less likely to trigger seizures. Because of the size of the screen and the way the equipment works it is rare for seizures to be triggered by watching films in a cinema, or by hand-held miniature screens. Interactive whiteboards, sometimes used in schools, have not been found to be a particular trigger for photosensitive epilepsy. What may be as important as the type of screen is what its happening on the screen. For example, a flickering image or changing geometric pattern on the screen could trigger a seizure. A seizure can sometimes happen by chance while someone is playing computer games or watching television, and may be a coincidence. Tiredness brought on by watching the screen for a long time, or excitement when playing computer games may also be a factor. Can disco lights trigger photosensitivity?Coloured lights do not usually cause a problem if they do not flash quickly. However, strobe (flashing) lights can trigger seizures, especially if it is dark. If you know you are photosensitive, it may be best to avoid strobe lights, or cover one eye if you are suddenly exposed to them. The Health and Safety Executive (HSE) recommends that strobe lighting in nightclubs or public performances is kept to a frequency of less than five hertz (flashes per second). How is photosensitive epilepsy treated?Photosensitive epilepsy usually responds best to the anti-epileptic drug sodium valproate (Epilim). If you know you have photosensitive epilepsy, the following tips might be helpful:
UK
Epilepsy Helpline: 01494 601400 ©
The National Society for Epilepsy |
How can I tell if I am photosensitive? What frequency of flashing light is most likely to trigger a seizure? What
patterns are most likely to trigger a seizure if I am photosensitive?
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