Are 3D screens bad for your kids?

Jeff Hecht, correspondent

Will playing 3D games on Nintendo's new 3DS game console ruin your child's vision for life? We may never know, but should you take the chance?

A statement first posted on the games company's Japanese web site cautions that children under age six should not use 3D features because the 3D effect could impair their development of natural binocular vision. Press reports range from straight accounts of the warning to complaints that no testing backs up the warning.

What are the facts?

It's been clearly demonstrated that 3D can make people sick. The nausea-inducing effects are more severe the closer the screen is to your eyes, the longer you watch, and the more extreme the effects. So staring at a hand-held game is more likely to be a problem than looking at a movie screen, but gamers are less likely to watch for a couple of hours without interruption. It doesn't matter whether the 3D effect depends on glasses, as in movies and most 3D TVs, or not, as in the Nintendo game.

Our visual systems do adapt to 3D after prolonged viewing, which can leave adults disoriented until their eyes re-adapt to the real world so they can perceive objects at the proper distance. It's a problem that's known to crop up with flight simulators and virtual reality.

Children's visual systems present a unique problem: they take many years to develop, and the process is far from thoroughly understood. It's known that kids who spend more time on outdoor activities are less likely to become nearsighted, so it's reasonable to suspect that outdoor activity also helps in development of depth perception - and that too much exposure to 3D screens could be a problem.

It should be noted that no research has shown that a hazard exists. But it's not ethical to conduct controlled tests of long-term effects of 3D exposure on children's vision, because there is a reasonable suspicion that they could cause harm. So we probably will never have a definitive answer.

What should you do? Be cautious. Nintendo provides parental controls so you can shut off the 3D effect, and they're probably worth using. Even better, keep the game out of little kids' reach - they would probably just break it anyway.