Epilepsy
Most people think of strobe lights when they think of seizures, but most people with seizures don't have any problems with strobe lights.
WDW doesn't actually use any lights that are technically strobe lights (i.e, fast, regular flashes of light) and they do not have any warnings for seizures and/or strobe lights on any attractions. Where they do have flashing lights, they are always irregularly flashing, which is a different situation.
Most true strobe lights flash many times per second, but slowing to 5 flashes per second or less means that the majority of even photosensitive epileptics are not going to have a problem. Only about 3-7% of people with epilepsy are photosensitive and have problems with lights; of those, only about 5% would have a problem with a light flashing 5 times per second or less.
Good article from the Epilepsy Foundation about epilepsy and lights/photosensitivity.
This is something to talk to your doctor with, but in for most people with epilepsy, the lights at WDW won't cause any problems. Some of the linked threads about epilepsy have information about lights in different attractions and other hints for avoiding seizures at WDW.
If you do encounter flashing lights and are concerned, the Epilepsy Foundation recommends
covering one eye and turning/looking away from the direct source of light. The reason for covering only one eye and looking away from the direct light is to prevent both eyes from sending exactly the same information to the brain.
Things that are very important to be aware of are sleep deprivation, dehydration and getting off schedule with medication. All of those things can lower the seizure threshold (how easy it is for a seizure to occur). It's very easy to get off schedule or forget medication while on vacation. One things we have found that helps with this is to actually use an individual dose medication container and an alarm (on our phone or iPod) as a reminder for medication times.
Stobe Lights and Epilepsy
Epilepsy at WDW