Thursday, February 22, 1990

Photosensitive Epilepsy

Photosensitive epilepsy is the name given to a form of epilepsy in which seizures are triggered by flickering or flashing light. It is often assumed that everybody with epilepsy is photosensitive, but only around five per cent of people with epilepsy are.

Most people with photosensitive epilepsy are sensitive to flickering around 16-25Hz. Hz is a measure by second. So if a person with photosensitive epilepsy of 16-25 Hz was to see light flickering 20 times per second, this could induce a seizure for that person.

So, what flickers in this range? Here are some common electronic devices and their "flicker rating" in Hz:
Modern Computer Monitor: 60 - 75 Hz
Modern Film Projector: 32 Hz
CTR Televisions: 25 Hz for the lines, 50 Hz for the screen
Strobe Lights: 4 Hz
Video Games: Depends on the game...
NYC Subway Train Cab Lights:

So how does a person avoid getting a seizure from flashing lights? Reduce the amount of flashing being processed by your brain. Her are some methods to do this:
1. Don't look at them
2. Move farther away from the lights
3. Cover one eye to cut the amount of brain being used by half
4. Wear polarized sun glasses
5. If it is a monitor or tv, get one that has a high Hz (flickers faster)
6. If you have to watch one with a low Hz, turn on other lights and move further away from the TV.