Photosensitive epilepsy is when seizures are triggered by flashing lights or contrasting light and dark patterns. Photosensitive epilepsy is not common but it may be diagnosed when you have an EEG test. Flashing or patterned effects can make people with or without epilepsy feel disorientated, uncomfortable or unwell. This does not necessarily mean they have photosensitive epilepsy.
How common is photosensitive epilepsy?
Around 1 in 100 people has epilepsy and of these people, around 3% have photosensitive epilepsy. This is when seizures are triggered by certain rates of flashing lights or contrasting light and dark patterns. Photosensitive epilepsy is more common in children and young people (up to 5%) and is less commonly diagnosed after the age of 20.
What is photosensitive epilepsy?
This is when you have a seizure straightaway, caused by being exposed to flashing lights or patterns. An electroencephalogram EEG can help with diagnosis, and may include testing for photosensitive epilepsy. This involves looking at a light which will flash at different speeds. If this causes any changes in brain activity, the technician can stop the flashing light before a seizure develops.
What rate of flashing light can trigger seizures?
Between 3-30 hertz (flashes per second) are the common rates to trigger seizures but this varies from person to person. While some people are sensitive at frequencies up to 60 hertz, sensitivity under 3 hertz is not common.
What patterns can trigger seizures?
Some people are sensitive to geometric patterns with contrasts of light and dark such as stripes or bars. Patterns are more likely to be a trigger if they are changing direction or flashing, rather than if they are still or moving slowly in one direction.
Flashing, flickering or patterned effects can make people with or without epilepsy feel disorientated, uncomfortable or unwell. This does not necessarily mean they have photosensitive epilepsy.
How is photosensitive epilepsy treated?
Photosensitive epilepsy usually responds well to anti-epileptic drugs (AEDs) that treat generalised seizures (seizures that affect both sides of the brain at once).
Managing photosensitive epilepsy
Possible triggers if you have photosensitive epilepsy
Flashing or flickering lights or images between 3 and 60 hertz (flashes per second).
A contrasting dark and light geometric pattern, such as black and white stripes or checks.
Factors that may increase the photosensitive risk
Tiredness, stress or excitement. For example, playing a video game for a long time without breaks.
The effect taking up all your field of vision. For example, being very close to a screen.
A light and dark pattern moving quickly, or changing direction, creating a disorientating effect.
Seeing the effect against a dark background, such as watching a screen in a darkened room.
If suddenly exposed to a trigger
Covering one eye completely with your hand will greatly reduce the photosensitive effect.
Safeguarding people from online harms
Epilepsy Society is calling on the Government to include safeguarding measures for people with photosensitive epilepsy in its Online Harms White Paper.
As social media continues to play an increasingly large role in modern life, this can bring with it extra challenges for people with epilepsy, especially for those who have photosensitive epilepsy. Here are some simple steps you can take to make using social media a safer experience.
Triggers are situations that can bring on a seizure in some people with epilepsy.
Sophie Harries, 22, is a dietitian from Somerset. She was diagnosed with photosensitive epilepsy at the age of 15. She explains how it affects her life.