In a seeming blink of an eye, 3-D technology has advanced beyond imagination. Hollywood, TV manufacturers and video game makers say you have to see it to believe it.

But the visual trickery that produces 3-D images can also lead to headaches, motion sickness and possibly impaired vision.

Game maker Nintendo acknowledged the concerns last week when it issued an unusual caution, even before its long-awaited 3DS hand-held game machine debuts in U.S. stores as soon as March.

Nintendo says children 6 years old and younger should not use the device because of the risk of lasting damage to ocular development.

No one really knows what the risk is, however, because there's scant research on how the latest wave of 3-D technology affects young eyes.

Nintendo touts its 3DS system as revolutionary: No dorky glasses required.

The breakthrough is made possible by tiny prisms embedded in high-resolution screens that scatter digital images into stereo visual 3-D.

Gamers can't wait to get their hands on the new portable console, and analysts predict brisk sales.

"It's going to be pretty impressive technology if it works the way they say it will," said Justin Chapman, a manager at the GameStop store near Sacramento's Pocket neighborhood.

Dozens of gaming enthusiasts have sought to preorder the device through the Freeport Boulevard store, but an official release date has yet to be announced.

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