Photosensitive Epilepsy

Today’s lifestyle can involve many hours each week spent watching television, playing video games or using computer monitors. While a seizure may occur in one of these circumstances, it may be a spontaneous or chance event not triggered by the television, video or computer monitor.

Photosensitive epilepsy is when seizures can sometimes be triggered by flashing or flickering lights, or by certain geometric shapes or patterns.

Some people have only ever had a seizure in the presence of a flickering light source of visual pattern, whereas others have had seizures with and without any stimulation of flickering light or visual patterns.

There is evidence that photosensitive epilepsy is inherited.

How is it diagnosed?
Photosensitive epilepsy is usually diagnosed by undergoing an EEG with strobe (flickering) light or pattern stimulation.
It is important to have expert diagnosis. Without this you may be restricting your lifestyle unnecessarily by believing that your seizures are triggered this way.

How is it treated?
In most cases seizures can be controlled by medication and avoiding known triggers.

What are the triggers?
Some known triggers for some people with photosensitive epilepsy are:

• Watching television or playing video games
• Having a faulty light or television that flickers
• Strobe lights
• Driving at dawn or dusk with sun shining through a line of trees
• Sun flickering on water
• Looking out of the window from a fast moving vehicle
• Geometric patterns

Other factors that come into consideration include:

• How fast and bright the flashing is
• How much field of vision is exposed to the light. A large television or sitting close to the screen, takes up more of a person's visual field and increases the risk of triggering a seizure in someone who is photosensitive
• Good background lighting is preferred whilst watching television or working on a computer or video game to help counteract the brightness of the screen

Managing photosensitivity
The following precautions only apply to those people who are diagnosed photosensitive.

Television: TV is the biggest problem for people who are photosensitive. The most important factor is the distance between the viewer and the set. Some useful tips include:

• Sitting too close to the TV screen causes the screen to fill the entire field of vision.
• Sit at least 2.5m from the TV screen in a well lit room.
• Sit at an angle rather than directly in front.
• Place a lamp on or behind the TV to reduce the contrast between the screen and the surroundings, even when watching during the day.
• Use a remote control or place a hand over one eye to lessen the effect of the flicker when manually changing settings.
• Do not watch the screen when fast forwarding, rewinding a videotape or adjusting the vertical hold.
• A smaller screen is preferable.
  Note: With more advanced technology, photosensitive seizures associated with television may be less of a problem. If you are considering purchasing a new television, sets with finer resolution are less likely to have flicker. LCD screens typically operate at only 60hz so flicker at this rate should not be an issue.

Television Content: The broadcast material itself may provoke a seizure. Things such as flashing sequences or rapid changes from light to dark or contrasting colours eg. blue and red.

Video Games: Current medical opinion is that video games do not trigger seizures unless there is an underlying tendency to have seizures. If this tendency exists, a seizure is likely to occur within the first 30 minutes of play. Generally, prolonged play is not a risk unless it is associated with sleep deprivation, which is a known trigger for seizures. TV screens used as monitors for video games may be triggers. Some useful tips include:

• Keep 2.5m from the screen.
• Play the game in a well lit room and reduce the brightness of the display.
• Avoid continuous exposure to the same pattern and playing when excessively tired.
• Check video games for epilepsy or seizure warning.

Computer Monitors: Most computer monitors rarely present a problem. Only in rare cases would it be necessary to restrict computer work. Tips:

• Use ordinary lighting rather than fluorescent.
• If you are sensitive to screen flicker on older types of monitors, a screen filter may help.
• High quality monitors, liquid crystal or LCD screens with a refresh rate of at least 60 Hz should not pose a problem.

Lights: The frequency of flashing light most likely to trigger seizures varies from person to person. Generally it is between 8-30Hz or flashes per second, but can vary for individuals.

Camera flashes rarely trigger seizures unless fired in rapid succession. It is also rare for seizures to be triggered by hand held screens or while watching a film.

Red flickering light and strobe or disco lights can trigger seizures, particularly if the room is darkened and there are other triggers such as stress, excitement, tiredness and/or alcohol. For those who are photosensitive the risk will depend on the speed at which the lights flash.

Responsible clubs and DJs generally display warnings if such lights are used and retail employers may turn off flashing lights in their store if requested.

Sunlight: Sunlight can trigger seizures in two ways: the reflection of light flickering off water or through leaves of trees; and light flickering through trees, posts or railings created by movement i.e. traveling in a car. Some useful tips include:

• Cover one eye with the hand to lessen the effect of flicker, as binocular (looking through both eyes) vision is needed to trigger a seizure.
• Polarised sunglasses also help reduce the risk.

Photosensitive facts and hints
Seizures can be triggered in many ways and not all of the listed hints may apply in each case. It is best to avoid particular situations known to trigger seizures.

Photosensitive epilepsy is rare.

• Seek expert diagnosis. Do not assume you are photosensitive as you may be placing unnecessary constraints on your lifestyle.
• 96% of people with photosensitive epilepsy are sensitive to flickering between 15-20Hz/flashes per second.
• Wear polarized sunglasses to reduce glare.
• Use a TV remote control.
• When watching or using TV, computers or video games, always ensure there is a light on so there is less contrast between the screen light and room light.
• If possible, reduce the brightness of the screen.
• In most cases seizures can be controlled with regular medication.
• Photosensitive seizures happen during not after the photic stimulation.
• Cover one eye to reduce the effects of flashing or flickering light.
• Most computer monitors do not present a problem.
• Seizures triggered by video games are most likely to occur within 30 minutes of play.
• Keep 2.5m from the TV or video game screen and 30 cm from a computer monitor.
• Take frequent breaks from video games and look away from computer/TV screens regularly.
• It is rare for seizures to be triggered by hand held screens or watching a film.
• Camera flashes rarely trigger seizures unless fired in rapid succession.
• Tiredness can also be a factor.
• Avoid excessive consumption of alcohol.
• If you feel strange, or like you may have a seizure, immediately turn off the game/computer or TV or look away.

References:
Erba, G (2006). Shedding light on Photosensitivity. One of epilepsy's most complex conditions. EpilepsyUSA Jan/Feb pp8-10.
Fish, D.R., Quirk, J.A., Smith, S.J.M. et al. (1994) National survey of photosensitivity and seizures induced by electronic screen games (video games, console games, computer-games) in Home and Leisure Accident Research Consumer Safety Unit, Department of Trade and Industry, London, H.M. Stationery Office, July.
Harding, G.F.A. www.epilepsytoronto.org/people/eaupdate
Jeavons, P.M., and Harding, G.F.A. (1975) Photosensitive Epilepsy, Heinemann, London.
Further information about seizure disorders and their management can be obtained from Epilepsy Action.

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