Robert S. Fisher, MD, PhD, FAAN, responds:
For about 3 percent of people with epilepsy, exposure to flashing lights at certain intensities or certain visual patterns can trigger seizures, according to the Epilepsy Foundation. Due to a condition called photosensitive epilepsy, lights can trigger seizures in one in 10,000 adults and one in 4,000 children and adolescents. Many people are unaware of a sensitivity to flickering lights or certain patterns until they have a seizure.
Discuss with Your Doctor
Most people who've been diagnosed with epilepsy undergo an electroencephalogram (EEG), which has its own flashing light. As part of a routine EEG, a strobe light flashes at different frequencies while a technician monitors the recording. Technicians usually alert patients about the potential for a reaction and monitor for it. If they see an electrical buildup on the monitor they know to turn off the lights.
Other Light Triggers
A flashing light is just one potential trigger. Other triggers include flickering or rolling images on a TV screen or computer monitor, video games or TV broadcasts containing rapid flashes or alternating patterns of different colors, and intense strobe lights like visual fire alarms. Natural light, such as sunlight, especially when shimmering off water or flickering through trees or through the slats of window blinds, can also trigger seizures in some people. Stripes of contrasting colors and flashing lights on tops of buses or emergency vehicles are other triggers.
Strategies for Avoiding Triggers While...
Watching TV: Watch in a well-lit room to reduce the contrast between light from the set and light in the room and sit as far back from the screen as possible. Avoid watching the monitor for long periods of time. If necessary, wear polarized sunglasses to reduce glare.
Playing video games: Sit at least two feet from the screen in a well-lit room and reduce the brightness of the screen. Do not play when tired. Take frequent breaks from the games and look away from the screen every once in a while. Do not close and open eyes while looking at the screen; blinking can trigger a seizure. Cover one eye while playing, alternating which eye is covered, and remember to turn off the game if strange or unusual feelings or body jerks develop.
Using a computer: Use a flicker-free monitor (LCD display or flat screen) and a glare guard. Consider wearing nonglare glasses, and take frequent breaks.
Recently, efforts have been made to reduce the risk of a seizure for people with photo-sensitive epilepsy. For example, warnings about the potential for seizures have been added to many video games, and flashing emergency lights can flash only once every two seconds, a frequency below the number needed to trigger a seizure.
Dr. Fisher is the Maslah Saul MD Professor of Neurology at the Stanford University School of Medicine in Palo Alto, CA, and director of the Stanford Epilepsy Center.
