Interesting stuff. I found watching Avatar in 3D i was straining at the beginning to see everything & started to get a headache.
I then found as i got into the story of the film i relaxed a bit, started seeing the 3d easier, & the headache went away.
....I then cashed the car on the way home swerving to avoid a 9 foot tall blue man with a tail. Knew i should have taken those damn glasses off.