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Photosensitive epilepsy

Contents 

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.

If you would like to see this information with references, visit the Advice and Information references section of our website or contact our Epilepsy Action freephone helpline on 0808 800 5050.

Code: 
B007.04

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.

  • Updated March 2015
    To be reviewed March 2018

Comments: read the 7 comments or add yours

Comments

I am wondering if what I am having is some sort of epilepsy or if its something else. Im 22 year old male. I was just out for a walk by myself when all of a sudden this house had many flickering lights outside of it. Instantly i feel lightheaded, dizzy (everything becoming bright, with twitching head over my eyes (like i feel the inside of my head moving), and heart racing breathing funny. Completely uncontrollable. I got to a bus stop so i could sit down and a minute later I felt fine again. What was happening in my head felt really scary.
This is not the first time it happened, but also before with other flashing lights. I was at a lighting exhibition where there was strobe lights and it happened again. I didn't see the sign for flashing lights. And it happens when I'm driving with low sunlight and trees. I have had to pull over a few times.
I am not sure if this is some form of underlying epilepsy or a part of my anxiety (i suffer badly from also). I know I should talk to my doctor about it but maybe i can et thoughts here. Luckily it doesn't happen to me so often.

Submitted by Alan on

Hello Alan
I can hear that this was scary for you, so it is great that you are looking in to this.

Some of what you have described can be experienced by people who have photosensitive epilepsy. The only person who can say for sure whether this is what is causing this though is a specialist doctor.

As you have said, it would be worth you talking to your GP about what happened. Your GP can then ask some questions which may help work out whether it was the anxiety you have been experiencing, or whether it may be something else. They can then refer you to a specialist doctor if they feel it is necessary. You may find our information about diagnosing epilepsy helpful: epilepsy.org.uk/info/diagnosis

If we can be of any more help, please feel free to contact us again, either by email or the Epilepsy Action Helpline freephone 0808 800 5050.

Karen
Epilepsy Action Advice & Information Team

Submitted by Karen, Epilepsy... on

I want to pulse LEDs in a ray-box to get extra brightness. This is for use in a school. If I set the frequency above 60Hz, will that be safe? Should a warning be attached to the ray-box?

Submitted by Old Frank on

A warning would be a good idea as there is a small possibility the flashing may be a problem for someone.

Cherry
Epilepsy Action Advice and Information team

Submitted by Cherry, Epileps... on

Thanks, Cherry. I'll set the frequency at 66Hz and put warning stickers on them. Let's hope that avoids all problems.

Submitted by Old Frank on

Hi, I am 22 and have photosensitive epilepsy. I was wondering if there are any current studies in the UK which need research participants who have photosensitive epilepsy? (I live in Leeds) Any information would be greatly appreciated.

Submitted by Anthony on

Hello Antony

We are not aware of any current research in to photosensitive epilepsy taking place at the moment. You may find it helpful to keep an eye on our webpage for future opportunities to take part in research.

You may want to take a look at the Epilepsy Research UK website which also has information about taking part in research.

Karen

Epilepsy Action Helpline Team

 

Submitted by todd at Epileps... on