With the premiere of the long-awaited (by some) Twilight: Breaking Dawn Part 1, several individuals have reported experiencing photosensitive epileptic seizures as a result of the flashing lights during the tense birthing scene in the movie. The instances occur due to the bright flashing lights of red and white, which can cause what are known as photosensitive epilepsy or photosensitive seizures.
Understanding Photosensitive Epilepsy
Photosensitive epilepsy is when your brain has an abnormal response to a certain sequence of flashing lights. The exact mechanism is not well understood, but it seems to be caused when flashing lights trigger a synchronized response in brain cells dedicated to processing visual signals. This synchronized response works like a laser to cause overexcitement in adjacent nerve clusters, which soon leads to the entire brain becoming seized, which results in blackouts and often motor responses.
What Light Triggers Photosensitive Epilepsy?
There is no single light or pattern of light that triggers photosensitive epilepsy. Many photosensitives will have trouble with a specific pattern of light. The chief frequencies for risk seem to be 15-20 Hz, but what frequency will stimulate an epileptic response varies from person to person and even from instance to instance for the same person.
One key seems to be the relaxation rate of the visual processing center of the brain. If processing cells remain excited for longer, it allows an accumulation of excited cells that ultimately leads to seizures.
Other photosensitives will experience problems with only a certain wavelength of light. Light of ~700 nm has been identified as a specific trigger for seizures. This is in the red part of the spectrum, so flashing red lights are often to blame for photosensitive seizures. Scientists suspect this is because light of this wavelength is processed by a special type of cone which is visually separate from other light-sensitive cones on the retina. There are three types of color-sensitive cones in the retina: red, blue, and green. Blue and green cones obviously have a significant amount of spectral overlap, but red is separate. According to the theory, when cones of one color are stimulated without stimulation of adjacent cones, the stimulus is magnified, which can lead to overexcitation. Testing the theory, researchers were able to trigger “epileptiform discharges” by stimulating only the green cones.
Other people have a quantity-of-light threshold. For these people it is the brightness of the light that ultimately triggers the epileptic response by overexciting all visual cells simultaneously.
What Stimulates Photosensitive Epilepsy?
Other than Breaking Dawn, some of the stimuli that have been shown to cause photosensitive seizures include:
- Video games
- Computer monitors
- Sunlight on water
- Light passing through picket fence posts
- Strobe lights at a club or theatrical performance
- Patterns of black and white lines, especially whirling or dartboard patterns
Television is the most common stimulus for photosensitive epilepsy. Half of sufferers in Europe report their first seizure after watching television.
Who Is at Risk
The most common victims of this type of seizure seem to be children, usually appearing between the ages of 8 to 20, with a peak around age 12 or 13, and a link with puberty has been suggested. Girls are more likely to be affected than boys. Overall the condition affects about 1 in 4,000 or 5,000 people, and about 5% of epileptics. There is some evidence to suggest that the condition may pass with age.
How to Avoid Seizures
You don’t have to skip Breaking Dawn to avoid the seizure risk, though if you’re looking for an excuse it’s certainly a good one. Instead, you can just cover your eyes during the scene, which is only a few seconds long, and has enough audio clues to ensure you won’t miss any information. For added safety, you can cover your eyes through the whole movie and you probably also won’t miss anything.
Here are some tips to avoid seizures in other circumstances:
- Keep your distance from flickering media (about 8 feet from the TV and a foot from your computer monitor). If you have to approach the TV, cover one eye–seizures require stimuli from both eyes.
- Make sure your monitor’s settings do not have too high a contrast and the refresh rate is at least 60 Hz.
- Always watch TV, play video games, or work on the computer in a well-lit room
- Reduce your exposure to fluorescent lights and make sure they get replaced when they begin to flicker at a visible rate
- Wear polarized blue sunglasses when exposed to flickering light
- Call ahead if you are attending a venue or performance that may have flashing lights
If you suffer from photosensitive seizures, talk to an eye doctor or neurologist about treatment options.