Light
flashes, light patterns and color changes can provoke seizures in 3% of people
with epilepsy. This is known as photosensitive
epilepsy.1 Is this you? Photosensitive
epilepsy is more common in children and adolescents, especially
those with generalized epilepsy and certain syndromes as juvenile myoclonic
epilepsy. It lessens as children age. Relatively few cases last into their
mid-twenties.
Many
people are not aware they are sensitive to flickering lights or to certain
patterns until they have a seizure. In some individuals, their seizures occur
only when triggered by certain photic, or light conditions. And in some
individuals this sensitivity may never progress to develop epilepsy. Some
people find they are sensitive to light exposure because they develop headache,
nausea, or dizziness induced by this light exposure. They do not develop
seizures and they do not have epilepsy. Brain scans usually are normal.
Light
triggers include flickering or rolling images on television and smartphone
screens and computer monitors, emergency vehicles, intense strobe lights like
visual fire alarms, natural flickering light off shimmering water, sunlight flickering
through tree leaves while driving, and through venetian blinds and certain
visual patterns, especially stripes of contrasting colors. Not all these visual
stimuli trigger seizures. Other factors are important, e.g., frequency of the flash, the brightness of the flash, its contrast
with the background, your distance from the light source, the wavelength of the
light and whether your eyes are open or closed. The resulting effect of the frequency
or speed of the inducing flashes varies from person to person. The frequency of
light triggers generally varies between 5 to 30 flashes per second.
If
flashing lights are uncomfortable for you a routine EEG can help find out why.
The EEG includes a period of flashing strobe lights at various frequencies
positioned in front of closed eyes as you lie on the bed in the EEG lab. An
abnormal EEG response to various frequencies of flashes indicates the presence
of photosensitivity which is an electroencephalography (EEG)
phenomenon or the photoparoxysmal response. This does not mean
you have epilepsy. If you are found to have this photosensitivity,
altering your daily activities can help to avoid your physical symptoms, as
avoiding intense videogame playing.
Helpful
tips to consider if you have photosensitivity include covering only one eye and
looking away. Closing both eyes will not help. Watch TV in a well-lit room to reduce
light-contrasts, sit far from the screen, wear polarized sunglasses while
viewing TV to reduce glare. Follow similar guides when playing video games. Do not
close and open eyes in front of the videogame as blinking may facilitate
seizures in sensitive people. Cover and alternate covering the right and the
left eye while playing at regular intervals. If you perceive strange or unusual
feelings or if body jerks occur, stop playing.
Regarding
computer monitors use one that is flicker-free (LCD or flat screen). Use a
monitor glare-guard. Wear non-glare glasses to reduce glare. Take frequent
breaks.
Strobe
lights are to be avoided if you can. If you can’t, cover one eye and turn away.
Visually
induced seizures remain significant public health hazards; they warrant public
education.
I
hope that this blog allows you to identify certain phenomena you experience but
could not explain before.
1.
Wirrell
E, Hernandez A. Photosensitivity and Seizures published by the Epilepsy
Foundation: September 30, 2019.
