On December 16, 1997 an episode of Pokemon was aired in Japan. As a result of this episode 685 viewers were admitted to the hospital, two of which remained in the hospital for a few weeks. Why? The animators created a sequence with a deep red color flashing between 5-30 Hz. The result was the triggering of seizures in people susceptible to the visual stimulus. Much of the ensuing panic was just mass hysteria, but there were definitely individuals who suffered either absent or tonic-clonic seizures as a result.
Photosensitive epilepsy doesn’t just occur in epileptics; anyone can be susceptible to them. Fortunately the phenomenon is very rare. What exactly causes the seizure? Well scientists have been able to identify various triggers for photosensitive epilepsy, but how hyper-excited images displayed on the retina translates to a hyper-excited brain we’re not quite sure. We do know that triggers depend on the frequency of the flicker, the intensity of the light, the area of flickering involved and the pattern of the image. The color and the distance between the source of the stimulus and the viewer also play a part in susceptibility.