Information about Photosensitive Seizure Disorders
What is a photosensitive seizure disorder?
Epilepsy is the most commonly known type of photosensitive seizure disorder, but there are others as well. These conditions are characterized by seizures exclusively provoked by flashing, intermittent light, and visual patterns.
How many people have photosensitive seizure disorders?
About one in four thousand people are diagnosed with photosensitive epilepsy. Not all people with epilepsy have photosensitive epilepsy. A person is not considered to have a photosensitive seizure disorder until they have had a seizure. The majority of sufferers’ first seizures occur between the ages of seven and fifteen years old. Photosensitive seizure disorder is twice as common in females as in males and is a function of binocular vision.
What can stimulate photosensitive seizures?
Certain flashing lights, images, and repetitive patterns may cause seizure in persons with photosensitive seizure disorder. Strobe lights, flicker of bright light through leaves, and sunlight flashing off of a series of windows are examples of known stimuli. Some people are known to be affected by the raster rate of cathode ray tube televisions, especially in Europe, where the standard is 50 Hz. Video content, whether on television, film, in computer games, or on the web, may include unsafe flicker, colors, or high-contrast patterns that induce seizure. For example, in 1997 a Pokéman episode broadcast in Japan showed a sequence of flickering images which triggered seizures in hundreds of children.
What current computer or web content guidelines or regulations have specifications regarding flashing?
- Section 508 of the Workforce Investment Act of 1998; sections 1194.21 (k) and 1194.22 (j) (computer software and web content)
- Web Content Accessibility Guidelines (WCAG) 1.0
- HFES 200 User Interfaces Standard (draft standard)
- ISO 9241-171 Software Accessibility Standard (draft standard)
- WCAG 2.0 (PEAT analysis matches the specifications used in WCAG 2.0)
Where can I find more information about photosensitive seizure disorders?
- Epilepsy Action – site maintained by the British Epilepsy Association, includes information about photosensitive epilepsy and television and other triggers of photosensitive epilepsy.
- Epilepsy Foundation –site maintained by the Epilepsy Foundation (U.S.), including tips on how to avoid photosensitive seizures
Funding for this work has been provided by the National Institute on Disability and Rehabilitation Research (NIDRR), U.S. Department of Education, under grant H133E980008.