Contents
- Introduction
- About photosensitive epilepsy
- About hertz (Hz)
- Diagnosing photosensitive epilepsy
- Ways to reduce the risk of seizures if you have photosensitive epilepsy
- Some possible seizure triggers for people with photosensitive epilepsy
- Computer and television screens
- Useful information and contacts
Introduction
The aim of this information is to tell you what photosensitive epilepsy is, who it affects and what might trigger a seizure if you have photosensitive epilepsy. There are also suggestions for reducing the risk of having a seizure.
About photosensitive epilepsy
Photosensitive epilepsy is a type of epilepsy, in which all, or almost all, seizures are triggered by flashing or flickering light. Both natural and artificial light may trigger seizures. Some patterns, like stripes or checks, can also trigger seizures for some people with photosensitive epilepsy.
Various types of seizure can be triggered by flashing or flickering light. These include tonic-clonic, absence, myoclonic and focal seizures. The most common is a tonic-clonic seizure. The seizure(s) will usually happen at the time of, or shortly after, looking at the trigger.
Around three in every 100 people with epilepsy have photosensitive epilepsy. It usually begins before the age of 20, most commonly between the ages of seven and 19. Photosensitive epilepsy affects more girls than boys.
Epilepsy Action has more information about epileptic seizures.
About hertz (Hz)
The word hertz (Hz) refers to how often something happens in a second. For example, it can mean the number of times something flashes or flickers in one second. It can also mean the number of times the scanning lines on televisions and computer monitors ‘refresh’ themselves in one second.
Most people with photosensitive epilepsy are sensitive to 16-25 Hz. Some people may be sensitive to rates as low as 3 Hz and as high as 60 Hz.
Diagnosing photosensitive epilepsy
If you have an epileptic seizure when looking at flashing or flickering lights or certain patterns, this is a sign that you may have photosensitive epilepsy.
Your doctor may ask you to have an electroencephalogram (EEG) test. This test records the electrical signals from your brain on an EEG machine. During the test, you will be asked to look at some flashing lights. If doing this changes the electrical signals in your brain, it may indicate that you have photosensitive epilepsy.
The person doing the test will usually try to stop the test before you actually have a seizure. However, there is a small risk that you will have a seizure when the test is done.
Epilepsy Action has more information about EEG tests and diagnosing epilepsy.
Ways to reduce the risk of seizures if you have photosensitive epilepsy
- Avoid looking at anything that you know may trigger a seizure.
- Avoid things that can increase your risk of having a seizure. These can include feeling tired or stressed, not having enough sleep and drinking alcohol.
- If you take epilepsy medicine, always take it as prescribed by your doctor.
- If you look at something that might trigger a seizure, don’t close your eyes. This could increase your risk of having a seizure. Instead, immediately cover one eye with the palm of your hand and turn away from the trigger. This reduces the number of brain cells that are stimulated and reduces the risk of a seizure happening.
Epilepsy Action would like to thank Professor G F A Harding, Emeritus Professor of Clinical Neurophysiology, Aston University and also Professor Stefano Seri, Professor of Clinical Neurophysiology at Aston University and Consultant at the Birmingham Children’s Hospital NHS Foundation Trust for their contribution to this information.
This information has been produced under the terms of The Information Standard.
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Updated March 2012To be reviewed March 2014
Comments: read the 5 comments or add yours
Comments
Are there any glasses that lessen the effects of strobe lights at a night club? Does covering one eye for the duration of a club session stop the effects ?
Hi Tom,
Covering one eye with the palm of your hand will stop seizures in most cases. But would this be practical for you to do this all night while at the night club? You could try an eye patch, as long as it keeps the lights out. There aren’t any glasses that we are aware of to stop the effect of flashing lights. Polarised lenses can stop the glare, but not the flickering or flashing of lights that can trigger seizures, in people with photosensitive epilepsy.
Advice and Information Team
My boyfriend has photosensitive epilepsy and the summer months are a total nightmare for him, as he always feels ill when he goes outside. He wears sunglasses and hats but it is awful. Does anyone know anymore abotu blue polarised sunglasses?
Hi, I dont know if you will be able to help me with this.....my son has been to a laser tag fun game centre twice recently, after the first time he got a headache, felt dizzy and sick, after his second visit, he had all the same symptoms as the first but was worse with a very high temperature, he couldn't stop shaking, although he was really hot and seemed a bit delirious?? I feel really bad now for not taking him to the doctors, but by the end of the following day, he was back to his normal happy self......do you think it could be the strobe lights that they use that seemed to affect him? Any kind of advice would be great, I have phoned the laser centre and they told me they haven't had any complaints from other parents, but in all fairness it only opened in February. Should I still take him to the doctors to get him tested for future reference? Kind Regards.
Hi Heidi
I certainly think it’s worth taking your son along to see his GP to discuss the symptoms that he had, even if it was a while ago. This way the doctor can decide if he needs to have tests for epilepsy. We can’t say if it was an epileptic seizure because of flashing lights, or not, as it’s such an individual condition. However, if he did have epileptic seizures because of flashing lights, they would have happened while he was in the laser tag fun game centre, or moments after seeing the lights flashing. Seizures that happen because of flashing lights are called photosensitive epilepsy. These seizures aren’t common and affect around three in every 100 people with epilepsy.
Whether your son has photosensitive epilepsy or not, the laser tag fun game centre could be advised that it would be good practice to place a warning for people with photosensitive epilepsy. That is if they use special effects such as strobe lighting.
Advice and Information Team