It doesn't happen all the time so I don't know if besides light what else might be a trigger. I only get the aura and it's not painful just not fun and puts me out of commission for 20-30 mins. I do feel out of it the rest of the day though. A sudden change in light is more apt to cause than a gradual change and adjustment. I will have to research and pay more attention when I get one. Thanks for your input, much appreciated.