The chief health concerns that might be raised by 3D movies (and the 3D televisions that are now on the market) have to do with headaches and eye discomfort that may be a problem for some people. For example, individuals with an eye muscle imbalance might find it uncomfortable to watch 3D movies. Here, the issue is simply one of depth perception. The brain normally handles spatial separation easily, but it might require more concentration and muscle effort for 3D viewing.
I haven't seen any studies documenting the incidence of these eye problems, but I have read that eye discomfort resulting in headaches and nausea is the reason 3D never took off when it was first introduced years ago. Today's digital technology reportedly has overcome these problems, but we'll have to see how many people experience discomfort with wider use of 3D in movies and television home theaters. I suspect the vastly improved production techniques really have made viewing more comfortable for those with the muscle and depth perception problems.
Even those with no eye muscle problems might find that watching 3D movies or television is tiring and causes blurry vision or headaches, according to results of a small study at the University of California, Berkeley. Normally, when we look at nearby objects our pupils converge; they diverge when we look into the distance. And all the while, the eyes have to focus. But Martin Banks, Ph.D., the UC-Berkeley professor of optometry and vision science who headed the study, says that watching 3D alters the way our eyes and brain perceive images. He notes that the recent hit 3D film "Avatar" was easy on the eyes because it drew viewers to focus on one object, but he wonders whether home 3D TV viewing will lead to the kind of fatigue, headaches and blurry vision his study revealed.
We'll have to wait to see how increasing use of 3D technology in the movies and at home affects us. If you find that watching a 3D movie in the theater is fatiguing and gives you headaches, you're probably better off avoiding them and not investing in 3D TV.
Andrew Weil, M.D.