Epilepsy Institute of NC info@eiofnc.org 336-659-8202

PHOTOSENSITIVE EPILEPSY

Photosensitive epilepsy is another type of epilepsy that can be caused by flashing or flickering lights.  Different patterns, like stripes and polka dots, can also cause a seizure.  Repetitive patterns like strobe lights, fluorescent lights that flicker, fireworks, and sunlight flickering through trees or on water are only a few patterns.

Types of seizures that can be triggered are tonic-clonic, absence, myoclonic, or focal.  Epilepsy medication can help control these seizures.  Another way to help is to turn your head away from the cause of the flickering.

According to the Epilepsy Foundation, (http://www.epilepsy.com/article/2014/3/shedding-light-photosensitivity-one-epilepsys-most-complex-conditions)

WHAT CAUSES LIGHT-INDUCED SEIZURES

  1. The flicker of the light source, and the “frequency” at which the light changes. In other words, how many times the light flashes in a second. Generally, flashing lights between the frequencies of five to 30 flashes per second (Hertz) are most likely to trigger seizures. In order to be safe, the consensus recommends that photosensitive individuals should not be exposed to flashes greater than three per second.
  2. The intensity of the light source, meaning how bright it is, as well as the “contrast” between light and dark during the flicker. The consensus recommends the contrast between alternating dark and bright images be not greater than 20 candelas per square meter (a technical measure for brightness).
  3. The area the light stimulus occupies in the visual field. This is important because it actually determines how much of the brain gets stimulated. For instance, in the case of television viewing at a distance of about nine feet, the consensus recommends the area of the flashing stimulus on the screen be not greater than 25 percent of the total area. This also explains why most affected individuals can prevent the photosensitive reaction by simply covering one eye (monocular vision).
  4. The pattern of the image. Static or moving patterns of discernable light and dark stripes have the same effect as flashing lights because of the alternation of dark and bright areas. The danger depends on how many and how contrasted the stripes are in the visual field. The consensus recommends no more than five pairs of stripes if they are moving within the field of vision and no more than eight pairs if they are static. About 30 percent of individuals sensitive to lights are also sensitive to patterns.

Distance from the source and the color of the source can be another cause of photosensitive epilepsy.

I usually close both of my eyes but I can still see the flickering.  It is not as bad, though.

More information can be found at, https://www.epilepsysociety.org.uk/photosensitive-epilepsy#.WLyEvPnytPY  and http://www.epilepsy.com/article/2014/3/shedding-light-photosensitivity-one-epilepsys-most-complex-conditions.

 

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