I have had photosensitive epilepsy for the past 16 years and have faced many problems because of it. I am mainly sensitive to the flicker of fluorescent lighting and as these dominate most shops and buildings they are difficult to avoid. My seizures are also provoked by flashing strobe light and looking at certain visual patterns.

What is photosensitive epilepsy?

“Photosensitivity is sensitivity to flickering or intermittent light stimulation but includes sensitivity to visual patterns. Photosensitivity therefore can be defined as recurrent convulsions precipitated by visual stimuli.” (Harding & Jeavons, 1994) Approximately 1 in 200 of the population has epilepsy and of these only a few per cent have photosensitive epilepsy. It is often assumed that everybody with epilepsy is photosensitive whereas in fact there are relatively few.

Factors that trigger seizures in photosensitive epilepsy

Television
Both natural and artificial sources of light may precipitate seizures but the most common trigger seems to be television and the playing of certain computer games. Early reports of epileptic seizures being provoked by watching television were said to be because the sets were defective and therefore flickered, or the vertical hold was faulty, causing the picture to roll. After more clinical investigations it has been found that seizures can also be provoked by a normally functioning television when the viewer is too near the set. The factor that is most important here is that the larger area of the retina of the eye which is stimulated by the flicker frequency of the picture is, in fact, functioning normally. The nearer the person is to the set, the more the picture is filling the whole field of vision and so there is more likely to be an abnormal response in the brain and therefore a seizure occurs.

Sunlight
Sunlight reflected off wet surfaces or through the leaves of trees, or seen when moving rapidly past trees or railings illuminated by sunlight shining from the side can provoke a seizure.

Flashing Lights
Flashing lights such as those used in discos and also fluorescent lighting may induce seizures.

VDUs
The amount of photosensitive seizures has increased since the introduction of Visual Display Units into the workplace and schools. Whereas the distance from a television set can be placed at 8 feet or more, it is not always possible to do so with a VDU because of the length of cable on a keyboard. The risk of a seizure occurring depends on the material being displayed. Most current computer displays have scan frequencies that are unlikely to provoke seizures. Computer displays with liquid crystal screens are flicker free. However there are still some computer games where a conventional television monitor is used and these have the same drawbacks as television. In general, the higher the frequency of the display screen, the better it is for a person with photosensitive epilepsy.

Visual Patterns
Sometimes people are sensitive to various geometric shapes or patterns e.g. stripes or checks Looking out of a window in a moving train can provoke a seizure as can looking at a moving escalator.

How can I tell if I’m photosensitive?

Most people are aware that they are. An E.E.G. is done with photic stimulation (flashing light) and photosensitivity is usual diagnosed at this stage.

Helpful hints

1. Seek advice from your doctor as the risk of seizures varies from person to person.
2. Covering or shutting one eye can reduce the effects of a flashing or flickering light.
3. Television should always be watched in a well lit room from a distance of 2.5 metres or more and it is helpful to place a small table lamp on top of the set. You should avoid approaching the television to adjust or switch channels. Again, you should cover one eye with the palm of your hand if you do have to go near the set. This is where remote control comes in handy. Sets with a higher frequency (100 hertz) or small screens (less than 14”) will also help.
4. Wearing polarised sunglasses outdoors in sunlight can reduce flickering reflections.
5. Avoid excessive tiredness as this may increase the risk of photosensitive seizures.
6. It is important to remember that reading from a computer screen for a long time can make eyes feel tired and this could provoke a seizure in some people. Regular breaks are advisable and anti glare screens are recommended for eyestrain.

I myself follow all the above guidelines and find them to be very helpful in the day to day living with photosensitive epilepsy. However it is important not to put blanket restrictions on all people with epilepsy, presuming that they are photosensitive. Although for those who have photosensitive epilepsy life can be restricted, it is still a relatively rare condition and unnecessary constraints on people’s lifestyles should be avoided.

References

Photosensitive Epilepsy, Graham Harding & Peter M.Jeavons
http://www.epilepsy.org.uk/info/photofrm.html
http://www.epilepsynse.org.uk/pages/info/leaflets/photo.cfm