What is photosensitive epilepsy?
In some people, seizures can be triggered by flashing or flickering lights, or by certain geometric shapes or patterns. This is called photosensitive epilepsy. Some people with epilepsy only have photosensitive seizures, whilst others may have other seizure types as well as photosensitive seizures.
This is a type of reflex epilepsy is seen in up to 5% of people with epilepsy, and because the seizures are usually triggered by some sort of visual stimulation, they can be reduced with simple avoidance strategies. Medication is usually used to help gain seizure control.
Although prognosis is generally very good, photosensitive seizures may persist.
How do I know if I have photosensitive epilepsy?
It is important to have a clear diagnosis, and keep good records or a seizure diary to help differentiate the seizures and their triggers. Photosensitive epilepsy can be diagnosed by having a routine EEG with strobe (flickering) light or pattern stimulation. A routine EEG should include this.
Today’s lifestyle can involve spending many hours using (visual) technology. While a seizure may occur in these conditions, it may also be a spontaneous or chance event – so don’t conclude your seizures are photosensitive seizures just because you had one or two when using technology.
How is it treated?
In most cases the photosensitive seizures can be well controlled by antiepileptic medication and avoiding known triggers.
What are the triggers?
Our modern environment is a rich source of potentially seizure-triggering visual stimuli. Typical sources can include:
- strobe lighting
- television, electronic or video games, or the images on the screen
- shimmering sunlight reflected off snow or water, or sunlight filtering through trees whilst in a moving vehicle
- venetian blinds
- striped walls or clothing
Less common stimuli are:
- moving escalators
- rotating helicopter blades
- faulty fluorescent lights
- welding lights
- mobile phone flashes
New potentially provocative sources turn up now and then unexpectedly.
What are other factors involved?
Whether or not a photosensitive seizure happens is also influenced by:
- whether the eyes are open, closed or closing at the time of the stimulation
- the speed or flicker of the flashing (light)
- the contrast and brightness of the stimuli – in general, with brighter stimuli and strong contrasts in colour, the more likelihood of inducing seizures
- how long the stimulation goes for – a seizure is more likely to occur with longer exposure
- the colour of the flicker (if any) – red flicker is more provocative and colour oscillating from red to blue
- how large and close the screen is – the larger and closer someone is, the more “field of view” it takes up and is more likely to trigger a seizure
Managing photosensitive epilepsy
Types of stimuli that may trigger a seizure
Almost all people with photosensitive epilepsy are sensitive to flickering lights. Many natural light sources can provoke epileptic seizures as well. With the increasing use of technology, there is more exposure to provoking factors (e.g. screen time, visual images and strobe lights) than ever before. Avoiding sources of triggers is the best advice.
The following precautions only apply to those people who are diagnosed with photosensitive epilepsy.
Television: There are many different types of screen technology, and modern television screens are much less likely to trigger seizures. An older cathode ray tube (CRT) TV created its picture with flicker and although not recommended, if you get very close to the screen you can see the flicker.
Liquid crystal display (LCD) and plasma screen televisions do not use the scanning lines and therefore are less likely to trigger seizures than the older CRT televisions. Plasma screens tend to be brighter and have higher contrast than LCD televisions; this increased contrast may increase the risk of seizure activation.
For people with photosensitive epilepsy, the current advice is to opt for an LCD TV over a plasma TV.
It is important to keep a good distance from any screen because seizures may be provoked by images on the screen such as, flashing sequences or rapid changes from light to dark or to contrasting colours, such as from red to blue, rather than from the screen itself. So, the further away you sit from the screen, the less likely a seizure will occur.
It has not been proven that 3D movies are any more likely to trigger a seizure than 2D movies if someone has photosensitive epilepsy.
- Sit at least 2.5 metres from a television screen in a well-lit room
- Sit at an angle rather than directly in front of the screen
- Don’t watch the screen in the dark
- Use a remote control or cover one eye to lessen the effect if you have to change channels manually
- Do not watch the screen when fast forwarding, rewinding or adjusting the vertical hold
- In the cinema, try to sit well back from the screen and near a light source, such as in an aisle seat where there is a guiding light
- Look away from any content that makes you feel uncomfortable
- A smaller screen set at low brightness and contrast is preferable.
In daily life, other factors such as sleep deprivation and drug or alcohol use may also play a role in provoking photosensitive seizures.
Video games: Apart from the screen display, the content and images of video-games are play a role in photosensitive seizures. Other factors that may play a role, particularly if the game is being played for a long time, include emotional excitement or tension, fatigue, eyestrain and difficulties sleeping, which can contribute to seizures.
Also, people tend to sit closer to a video game screen than when watching a TV program.
- Sit as far away from the screen as possible
- Play the game in a well-lit room and reduce the brightness of the display
- Avoid continuous exposure to the same pattern and don’t play when overtired
- Check games for epilepsy or seizure warnings
- If you do find that a game(s) makes you feel like you are going to have a seizure, then it is best to stop playing and keep exposure to the game in short bursts (have a break every 10-15 minutes) or avoid that particular game altogether.
It is good to take regular breaks from any electronic games and refresh.
Computer monitors: It is uncommon for a computer screen to trigger a seizure. Only in exceptional cases would it be necessary to restrict computer work. If you are sensitive to screen flicker on older monitors, a screen filter may help. You could always try an anti-glare filter to reduce screen glare. High quality monitors, liquid crystal or LCD screens with a flicker (refresh) rate of at least 60Hz may not pose a problem. Once again, it is more likely to be the images on the screen that may cause a seizure.
It is uncommon for seizures to be triggered by hand-held screens.
3D movies: There is much hype and concern about the effect of 3D movies being a seizure trigger, but this is not the case. In people with photosensitive epilepsy, the risks of a seizure being triggered by 3D movies is no greater than conventional 2D programmes. For people with non-photosensitive epilepsy the risk of 3D movies triggering a seizure is negligible.
Lights: The frequency of a flashing or flickering light most likely to trigger seizures will vary from person to person. Generally it is between 8-30 flashes per second, but this can vary. Many people seem to be sensitive around 15-20 flashes per second. Again, it is also dependent on the brightness and intensity of the light, and how long the person is exposed to it.
Ordinary lighting in a room is preferable to fluorescent, but faulty fluorescent lights are rarely the trigger of a seizure
Fans: Ceiling fans in a lit room can create a flicker effect. A pedestal fan is best if you feel the ceiling fan may trigger a seizure.
Geometric patterns: Some people are sensitive to geometric patterns which have strong contrasts of light and dark such as stripes or checks. Some of these patterns can create an optical illusion. Some buildings and public places may have large areas like this, such as carpet. The average person will just feel some visual distortion, but if you feel strange in this environment, it is important to leave or at least cover one eye.
These patterns may also be on a television 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.
Camera flashes: These rarely trigger seizures unless fired in rapid succession.
Red flickering light and strobe/disco lights: These can trigger seizures, particularly if the room is darkened and there are other triggers such as stress, excitement, tiredness, sleep deprivation and alcohol. For those who are photosensitive, the risk will greatly depend on the speed of the flashing light.
- It is sensible to avoid strobe lighting like those at nightclub’s and music festivals if you have photosensitive epilepsy, but this is a common social activity for young people, so it may be a hard one to resist. Some people these events even if they are photosensitive, and find they can tolerate it. Responsible clubs and DJs may display warnings if these lights are used and retail employers may turn off flashing lights in their store if requested.
Sunlight: This can trigger seizures in a number of ways such as: the shimmering of light off water or through leaves of trees, and light flickering through posts or railings when moving quickly, such as travelling past in a vehicle. Some people may even be affected by looking outside through a screen door.
- Cover one eye with the hand to lessen the effect of the flicker as binocular (looking through both eyes) vision is needed to trigger a seizure.
- Polaroid sunglasses or Zeiss Clarlet F133 Z1 Blue lenses may also help reduce the risk.
Knowing what sources may trigger your photosensitive seizures, and reducing your exposure to them plays a significant role in reducing or stopping this type of seizure. Many people still need medication, but try to:
- Avoid events with strobe lighting if you can
- Avoid video games with high contrast flashing and have frequent breaks if playing video games
- Cover or patch one eye if you cannot avoid certain sources of stimulus (eg travelling in a vehicle when sunlight is flickering through the trees)
- Wear glasses that reduce the amount of light as much as possible, such as polarised sunglasses
- Blue lenses, (type Zeiss Clarlet F133 Z1), have proven effective for many people
- Use smaller TVs and computer screens. Ask about specific computer screens when purchasing a computer
- Reduce the contrast of TV and computer screens
- Use a remote control
- Keep a good distance to any screen (ideally at least three times its width)
- When using any screen, keep the room well lit.
These are general suggestions, and depending on your sensitivity, not all approaches may be necessary or effective.
For more information go to:
Factsheet: Photosensitive Epilepsy