Some viewers have complained of headaches and eyestrain after watching 3D films. There have been several warnings, especially for the elderly. Motion sickness, in addition to other health concerns, are more easily induced by 3D presentations.
There are primarily two effects of 3D TV that are unnatural for the human vision: crosstalk between the eyes, caused by imperfect image separation, and the mismatch between convergence and accommodation, caused by the difference between an object's perceived position in front of or behind the screen and the real origin of that light on the screen.