The claim: The epic science-fiction film Avatar has had some unwanted side effects.
Many viewers have complained that Avatar and other 3-D films give them headaches, nausea, blurred vision and other symptoms of visually induced motion sickness.
The problem, studies indicate, is that the films often cause unnatural eye movements.
Normally, when an object approaches a person, the eyes respond in two ways,. They converge, or rotate inward to follow it.
At the same time, as the object approaches, the eyes focus and maintain a clear image of it by changing the shape of the lens, a process called visual accommodation.
However, a 3-D object flying off the screen causes sensory conflict. The eyes rotate inward to follow it, but they must also maintain a fixed focus on the display surface. So they converge without accommodating, an uncoupling of two natural processes that - over the course of a long movie - can be stressful.
Film buffs who have sat through multiple screenings of Avatar say one trick is to avoid looking at unfocused parts of the scenes, which sounds a lot easier than it is.
The bottom line: 3-D movies can cause unnatural eye movements that induce strain and sickness.
- The New York Times