| You have photosensitive epilepsy if your seizures are triggered by exposure to
flashing or flickering light. Although it is widely believed that all people
with epilepsy are photosensitive, in fact this is true for only about 3 - 5%.
Photosensitive epilepsy is most common in children and teenagers.
Seizures in photosensitive people may be triggered by
exposure to such light sources as television screens (especially those that
flicker or images that "roll"), certain computer or arcade games, alternating
patterns of different colours, flickering fluorescent tubes and flashing strobe
lights such as those used in fire alarms or nightclubs. Sometimes seizures are
triggered by natural light, for example sunlight flickering through trees or
railings when you move rapidly past them, or light reflecting off water. The
most common trigger culprit, however, appears to be television screens.The light sources mentioned above will not
invariably induce seizures in a photosensitive person; there are various
contributing factors, which include:
- the frequency of the
flashing or flickering light (how quickly the light flashes). Frequencies
between 5 to 30 flashes per second (hertz) are most likely to trigger seizures,
although this varies among different individuals.
- brightness of the
flashing light
- the level of background lighting
The likelihood of flashing lights such as those used on
emergency vehicles triggering seizures is considered to be small, because the
distance between the light source and the viewer is usually quite large. It is likely that you will be tested for photosensitivity
when you are initially diagnosed with epilepsy. During the electroencephalogram
(EEG) test, the electrical activity in your brain is recorded while you are
exposed to flashing lights at various intensities. Avoiding light-induced seizures
If
you have photosensitive epilepsy, your doctor may advise you to avoid exposure
to certain types of flashing lights, and to avoid places or activities where
flashing lights are likely to be encountered (such as nightclubs). The following
measures may also be helpful in reducing the incidence of light-induced
seizures:
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