Quote Originally Posted by Sir Terrence the Terrible
When you sit too far away in a dark room(the proper way to watch movies), and you have a bright source constantly changing light levels in darkness, that is the problem as it makes the pupils rapidly have to adjust to the changing light levels. When you sit closer, there is more light hitting the pupils, which allows them to stay more open, and not have to rapidly adjust to constant changes as much, no eyestrain is the result.
This is just some thoughts (non projection TV), but I imagine sitting closer to TV (to fill in the field of view) would intensify the light that is hitting pupils in a dark room, thus pupils still have to adjust from darker scene to lighter scene. I still don't see how moving closer to TV would reduce constant change of pupils which is source of eye strain.

I agree with Pix that if planning to use an ambient light behind TV, the wall behind TV should be painted 6500k color temperature to accommodate the color temperature of calibrated TV.