Giuseppe Erba, MD, is a Professor of Neurology and Pediatrics at The Epilepsy Center, Strong Memorial Hospital at the University of Rochester, Rochester, NY. A leading expert on photosensitivity, he recently spoke with epilepsy.com and offered precautionary advice for those with epilepsy who are anticipating July 4th fireworks.

Fireworks, flags, video games and even early evening or night driving appear to carry a certain risk for people with epilepsy. Dr. Erba explained how it is that some people watching fireworks might find that the display triggers a seizure. He pointed out that for this to occur requires the right stimulation, mainly high luminosity against a dark background, the high frequency of the flicker, for example, greater than three flashes per second, and closeness to the source of light. He added, “The color of the fireworks also makes a difference, for instance green and blue are better than red and blue, but the bright white lights are the most provocative.”

Dr. Erba said, “Any strong light that flashes repeatedly and consistently into the eyes of a photosensitive individual can potentially cause a seizure. Many people do not know that they are photosensitive until this combination of factors triggers a seizure.”

However, regarding the relationship between fireworks and seizures, he emphasized, “I am not aware of case reports regarding fireworks triggering seizures, but theoretically I think that this is possible. The dangerous portion of the display is the final barrage. This is when they blow up many fireworks at the same time. At that point we have the combination of critical factors -- the sky is very dark, perhaps even pitch black. There is a strong luminosity. And the flicker effect is at a maximum – as occurs when many flashes of bright white light explode in different parts of the sky almost in unison. This is the most potentially dangerous combination,” he said.

Dr. Erba likened the grand finale of a fireworks display to “a powerful strobe light” effect.

Precautions before fireworks

There are three ways that people viewing fireworks can protect themselves or their children.

Distance: Dr. Erba said, “People can stand at a variable distance from the fireworks display. If fireworks are watched from enough distance so that the display barely gets above the horizon, there will be no danger because the stimulus occupies a small fraction of the whole field of vision.

However, in order to fully enjoy the spectacle, most spectators choose to sit much closer. To be safe, people at risk -- particularly children -- should place themselves far enough away from the fireworks so that the display will extend to no more than half of the sky in front of their eyes. In this situation, any potential risk is virtually eliminated.”

Medication: “For those individuals with epilepsy who are on medication, particularly Depakote, it is fairly safe to view fireworks, because Depakote is highly protective,” said Dr. Erba. “However, they must make sure that they took the medication properly the day before and the day of the fireworks. If they are skipping and forgetting they may think they are protected, but they are not because the level of medication has dropped.”

Covering one eye: “The closer the eyes are to the source, the larger is the portion of the retina that gets activated and consequently the part of the brain that gets stimulated,” said Dr. Erba. He also told us that covering one eye reduces the amount of visual stimulation and the risk. “However, if one is at a fireworks display and feels the symptoms of a seizure, such as the body jerking out of control, that person should cover both eyes promptly,” he noted.

Flags, video games, and traffic

It seems that there are other situations of visual stimulation that can possibly trigger seizures.

Flags: According to Dr. Erba, “If one is close enough and is staring at the white and red stripes of the American flag such that the stripes occupy the whole eye field and with a high level of luminosity, some people may start twitching. Only about 30 to 40 percent of people sensitive to lights are also photosensitive to patterns,” he said. “If a flag is constructed with a low number of alternating stripes that are widely spaced then you must consider that 2 or 3 stripes will act like the strobes flickering at 2- 3 per second, which is safe. But it you have 13 stripes then it is like a light that flickers 13 times per second, which carries more risk for photosensitive individuals. However, you would need to be very close and fixate on the stripes in full bright light for there to be any danger.”

TV and Video games: The distance from the television that Dr. Erba recommends for children is 5 feet or more from the television screen. “You want a display that occupies half or less than your field of vision. Video games are watched at close distance and carry the additional risk of rapidly changing combinations of contrasting colors that may be very provocative.”

Driving: The same type of conditions with flickering lights – that might trigger a seizure at the fireworks – may occur with driving either at night or riding in a car along a line of trees with low setting sunlight, creating that flickering or dappled light effect. “Whether it is an image on a TV screen or fireworks displayed in the sky, or night traffic, covering one eye has an immediate protective effect,” said Dr. Erba.

Genetic predisposition

For most people with epilepsy, the risk of a seizure during fireworks may be very small. However, for those with a predisposition to photosensitivity and a family history of seizures, especially the inherited form of generalized epilepsy -- then the risk increases. “But by taking precautions, you won’t prevent those people with epilepsy who want to view fireworks from enjoying the display,” he concluded.

(To learn more about photosensitivity please go to: Shedding Light on Photosensitivity, One of Epilepsy's Most Complex Conditions)

Edited by Steven C. Schachter, MD