A friend of mine has epilepsy as a result of a brain injury he received as a child. It was a car accident that he survived but he experienced trauma to part of his brain.
As a result they put him on seizure medication as part of his epilepsy treatment. He said that he does fine on the medication but that he must avoid certain triggers as well.
Flashing lights, especially with video games or even in movies, can trigger seizures to the brain. I think this is because the flash of the lights somehow synchronizes with the electrical activity in the brain and this sets off the seizures.
I think that’s unfortunate because that means he must avoid certain activities to avoid the onset of the seizures. For movies, he just avoids going to the theaters. If he rents them out on DVD and watches them at home he can withstand the special effects better.