Photosensitive epilepsy

Photosensitive epilepsy (PSE) is a form of epilepsy in which seizures are triggered by visual stimuli that form patterns in time or space, such as flashing lights, bold, regular patterns, or regular moving patterns.

PSE affects approximately one in 4,000 people (5% of those with epilepsy).

Signs and symptoms

People with PSE experience epileptiform seizures upon exposure to certain visual stimuli. The exact nature of the stimulus or stimuli that triggers the seizures varies from one patient to another, as does the nature and severity of the resulting seizures (ranging from brief absence seizures to full tonic–clonic seizures). Many PSE patients experience an "aura" or feel odd sensations before the seizure occurs, and this can serve as a warning to a patient to move away from the trigger stimulus.

The visual trigger for a seizure is generally cyclic, forming a regular pattern in time or space. Flashing lights (such as strobe lights) or rapidly changing or alternating images (as in clubs, around emergency vehicles, near overhead fans, in action movies or television programs, etc.) are examples of patterns in time that can trigger seizures, and these are the most common triggers. Static spatial patterns such as stripes and squares may trigger seizures as well, even if they do not move. In some cases, the trigger must be both spatially and temporally cyclic, such as a certain moving pattern of bars.

Several characteristics are common in the trigger stimuli of many people with PSE. The patterns are usually high in luminance contrast (bright flashes of light alternating with darkness, or white bars against a black background).