Neuro-Visual Conditions
Photosensitive Epilepsy
For most people, a strobe light at a concert or sunlight flickering through the trees is just part of the scenery. For someone with photosensitive epilepsy, the same moment can trigger a seizure.
Here's what the condition is, who it affects, how it's diagnosed, and the everyday tools that help people live with it.
The Basics
What Is Photosensitive Epilepsy?
Epilepsy is a neurological condition in which abnormal electrical activity in the brain causes recurring seizures. It's the fourth most common neurological disorder, after migraine, stroke and Alzheimer's disease.
Photosensitive epilepsy (PSE) is a type of reflex epilepsy, which means seizures are set off by a specific trigger. In PSE, that trigger is visual: flashing or flickering light, or bold, high-contrast patterns. Doctors call the brain's abnormal reaction a photoparoxysmal response, or PPR. PSE isn't a separate diagnosis. It's a sensitivity some people with epilepsy have, and most people with epilepsy aren't photosensitive at all.
Who Gets Photosensitive Epilepsy?
PSE is fairly uncommon. The Epilepsy Society estimates it affects about 3% of people with epilepsy, and some studies put the figure as high as 14%.
It usually appears in childhood or the teenage years, most often between ages 7 and 19, and it's more common in girls and women. It's closely linked to certain genetic generalized epilepsies, including juvenile myoclonic epilepsy and Jeavons syndrome.
The encouraging part: for many people, photosensitivity eases with age, and it tends to respond well to treatment.
Symptoms
What a Seizure Can Feel Like
Light-triggered seizures often involve both sides of the brain, and the most common type is a generalized tonic-clonic seizure. Some people notice a warning sign first, called an aura. Symptoms vary from person to person and can include:
- Dizziness or lightheadedness
- Changes in vision
- Headache
- Nausea
- A strange taste in the mouth
- An out-of-body feeling
- Jerking of the arms and legs
- Muscle spasms or stiffening
- Clenched teeth
- Rapid eye movements
- Falling or loss of consciousness
- Loss of bladder or bowel control
Seizures also carry real risks, like falls and injuries, and the worry about the next one can make driving, shopping or a night at the movies feel out of reach. Many people also notice changes in their vision before or during a seizure.
Not Every Reaction Is a Seizure
PSE vs. Visual Discomfort
Plenty of people get a headache or feel queasy around harsh, flickering light. The difference is control. With ordinary visual discomfort, you can look away and the symptoms fade. With photosensitive epilepsy, once a seizure starts it has to run its course.
That's why prevention matters so much: avoiding triggers, and filtering the light that reaches the eyes.
PSE is also different from photophobia, a painful sensitivity to light that doesn't cause seizures.
Not Every Reaction Is a Seizure
How It's Diagnosed
A neurologist usually confirms PSE with an EEG, a test that records the brain's electrical activity. During the test, a strobe light flashes at different speeds, called intermittent photic stimulation, to see whether it brings on a photoparoxysmal response.
CT or MRI scans may also be used to rule out other causes.
Managing PSE
How It's Managed
Know Your Triggers
Learn which lights and patterns cause trouble, which usually don't, and simple habits that lower the risk at home and out and about.
Triggers and preventionEpilepsy Glasses
Z Blue lenses filter the light most likely to trigger a seizure. In a study of 610 patients, they stopped the brain's response to flashing light in about 3 out of 4.
How Z Blue lenses helpEpilepsy and Vision
Seizures can change how you see before and during an episode, from auras to eye movements and visual illusions.
How epilepsy affects visionPhotosensitive epilepsy usually responds well to treatment. A neurologist may prescribe anti-seizure medication, and day-to-day life gets easier with a few more tools.