Photosensitive epilepsy is the term commonly used for people who have seizures triggered by flashing or flickering lights and patterns. Due largely to its depiction in TV and film, it’s also a type of epilepsy trigger that many people think is an extremely common trigger. Although it affects around 20,000 people in the UK alone, it’s not quite as common as many people might think with only 3 in every 100 people with epilepsy being affected.
Some people with photosensitive epilepsy are affected solely by flashing lights and patterns, this is known as ‘pure photosensitivity’.
Although many people can be affected by flashing or flickering lights as a trigger, the flash or flicker rate that affects them can vary from person to person. Rates between 16 and 25 flickers per second are the most likely to trigger a seizure in someone with photosensitive epilepsy, however, rates as low as 3 or as high as 60 have been known to cause seizures in some people.
In some cases, patterns are more likely to trigger a seizure, typically those with highly contrasting colours or those that move are most likely. For example, a heard of zebras moving at the same time could trigger a seizure. Again, this can vary from person to person.
Photosensitive epilepsy is known to have a genetic aspect that can be inherited. Also, if there is a family history of juvenile myoclonic epilepsy you could be more at risk.
There are also a number of epilepsy syndromes that are far more at risk of photosensitivity as a trigger, these are:
Photosensitive epilepsy is developed mostly in people between the ages of 7 and 19, however, there are cases where it develops much later in life. Females are more likely to develop photosensitive epilepsy than males.
The most common way to diagnose photosensitive epilepsy is the use of an electroencephalogram (EEG) test. An EEG monitors brain activity and records electrical signals whilst flashing lights are used to determine whether the brain patterns change in a way that suggests photosensitive epilepsy.
Epilepsy medications (AEDs) are commonly used to treat photosensitive epilepsy. These medications can be used to reduce the number of seizures or in some cases these may completely stop.
Avoiding the trigger altogether is the safest course of action, however, this is not always possible. A person with photosensitive epilepsy who is faced with flashing lights is advised to cover one eye with the palm of their hand to reduce the number of brain cells that can be stimulated. Turning away from the lights or closing your eyes could cause a flicker effect that stimulates the brain cells further.