by Robert S. Fisher, M.D., Ph.D.
We have just finished the holiday season and many of our lucky children will have received videogames or flashing toys as presents. Are these games a risk for provoking seizures? I had the opportunity to participate in the formulation of consensus opinions of experts on photosensitive seizures, under the sponsorship of the Epilepsy Foundation of America. These consensus opinions were published in the scientific journal Epilepsia a few years ago (2005, volume 46, issue 9, pages 1423-1425) but these are in a technical format. Here are some non-technical summary facts about photosensitive seizures and what you can do to avoid them.
A photosensitive seizure is defined as a seizure produced by flashing lights or certain visual patterns, for example moving stripes. About 3% of people with epilepsy overall will have photosensitivity that can be seen in their brainwave pattern (electroencephalogram or EEG) when lights are flashed. Not all people who have photosensitivity in their EEG will actually have a seizure in real life from flashing lights. Among an unselected population of all people in the community, about 1 in 10,000 adults and 1 in 4000 children might actually have a seizure sometime from flashing lights. Therefore, the population risk is low, but if you are susceptible, it can happen to you.
Photosensitive seizures can happen in people who do not even know that they have a seizure tendency, until it occurs. Light stimulation can provoke seizures, but it does not create epilepsy. Epilepsy is the tendency to have spontaneously recurring seizures, which is built into the characteristics of the person with epilepsy. Flashing lights simply provoke seizures in susceptible individuals.
The most common stimulus that can provoke a seizure is bright light flashes at frequencies between 10 and 25 flashes per second. Some people are susceptible to flash frequencies as low as one per second and some as high as sixty per second. The light must be bright and close enough to fill a large part, at least 25%, of the person's visual space. White light flashes are usually brightest, but some people are particularly susceptible to red light flashes or alternation between red and blue flashes. Such red and blue flashes in the so-called "rocket launch sequence" of a Pokémon cartoon in 1997 sent about 700 Japanese schoolchildren to the hospital with immediate seizures or other reactions. Some photosensitive individuals react more to patterns than to flashing lights. Vertical moving stripes, or moving dots may bring on a seizure. This can happen with light coming through window blinds or shimmering on a water surface.
Three common sources lead to possible photosensitive seizures: the environment, television and video games. An example of seizures from the environment would be sunlight flashing through rows of trees as you drive by. Faulty fluorescent lighting that flickers visibly or intentionally flashing lights in a discotheque are other environmental examples. Flashing fire alarms can provoke seizures, but the flash frequency has been reduced to less than three per second, so this is now unlikely. Television can provide flashing in two ways. One is the flickering of the picture itself, and the other is flickering of content that is shown on TV programs. Because of highly publicized television-induced seizures in Japan and the United Kingdom, these countries now screen video broadcast material for a potential to provoke seizures. No systematic method to do so is currently used in the United States, although individual studios and broadcast networks have their own safety screening programs. Flashing scenes in movies have not been as much of a problem because movies are overall darker than TV pictures.
Video games are harder to regulate than are TV broadcasts because people can play the game in so many different ways. If you make a character jump up and down in front of the sun it may produce repetitive flashing while playing the game. It is impossible to prescreen every pathway that someone might take while playing a particular game. The major video game manufacturers are aware of the potential of videogames for producing seizures. They provide warnings for susceptible individuals and work with videogame content creators to minimize the chances that a game could provoke a seizure. But that risk cannot be reduced to zero, except by not playing the game.
What can a person with epilepsy or parent of a child with epilepsy do to minimize the risk of a photosensitive seizure? One possibility is to eliminate videogames and TV. But the majority of children with epilepsy do not have seizures when playing video games or when exposed to flashing lights or patterns. Safety of particular games or TV shows can be known from personal experience or from testing the child with bright light flashes during recording of an electroencephalogram. Children who are not known to be susceptible to photosensitive seizures probably shouldn't have to endure the additional stigma of avoiding videogames, when all their friends are playing them. This has to be an individual decision made among parent, child and the child's physician. Here are some reasonable general precautions:
- Avoid bright flashing lights in the frequency range 10-25 per second. Look away or cover your eyes when exposed to such flashes. Covering one or both eyes is more effective than is closing the eyes, since bright flashes often penetrate the closed eyelids. Avoid playing video games that have precipitated seizures in the past.
- Sit back at least 2 m (about 6 feet) from the TV screen or videogame screen.
- Play in a well-lighted room so the contrast of the TV or videogame with background lighting is not too high.
- Playing a videogame with one eye covered, for example by an eye patch, is useful to avoid light-induced seizures.
- Take breaks from game-playing, with no more than one hour straight playing at a time, followed by a 15 minute break. Avoid playing when very tired, or when first arising in the morning, because these are more likely times to have a seizure.
Do not overreact with blanket prohibitions that may be unnecessary for a particular person. As with so many things pertaining to epilepsy, know what is safe for yourself or your child and guide your behavior accordingly.