Stereoscopic 3D video games and movies make your eyes do weird things to create the illusion of depth. As a result, for some, 3D viewing elicits a feeling of imbalance, disorientation or a general indication that lunch is on its way back up.

But beyond those short-term effects, with 3D televisions hitting the market and Sony and Nintendo releasing 3D stereoscopic video games, is there risk of permanent eye damage from exposing eyeballs to the faux third dimension for prolonged periods of time?

"It's not likely to cause any permanent harm to vision," said Dr. Mark Borchert, a respected L.A.-based ophthalmologist with the American Academy of Ophthalmology, talking to Gamasutra. He was named as one of the best doctors in Southern California by the L.A. Times in 2009.

"There are people who get uncomfortable with it, and get eye strain or headaches, or on much rarer occasions, a sense of imbalance or nausea, but there's no evidence it can cause permanent harm to your vision or use of both eyes together or anything like that."

That's good news for video game companies. 3D is poised to be one of gaming's next big things -- Sony is pushing internal developers to create PlayStation 3 games with 3D effects, and the Nintendo 3DS handheld was the buzz of the E3 convention earlier this year.

Borchert, who is also a doctor at The Vision Center at Children's Hospital Los Angeles, wasn't so sure about the impact that 3D stereoscopic effects could have on young children, however. Recently Nintendo of America president Reggie Fils-Aime recommended that kids under about the age of seven should avoid viewing 3D images.

"...This is the same messaging that the industry is putting out with 3D movies, so it is a standard protocol," he told Kotaku at E3. The upcoming Nintendo 3DS has a slider that lets users turn the 3D effect up, down or completely off.

With young gamers being a large target audience for Nintendo handhelds, any harmful effect of 3D on kids' peepers could have a negative impact on the company. Dr. Borchert explained, "Children are not born with the ability to use both eyes together, they do not have any true binocularity at birth, and they certainly do not have stereoscopic vision." It is possible that 3D could harm developing eye muscles.

But while Borchert admitted that ophthalmologists "don't have an answer" to the negative effects of 3D effect viewing on young children, the expert pegged the appropriate 3D viewing age even lower than Nintendo.

"[Binocularity and stereoscopic vision] is something that is learned in the first few years of life, primarily in about the first three years of life. So it's unlikely that children at that age, where stereoscopic vision is developing most critically, are going to be playing these games."

He said that the move to 3D does raise questions about more accessible 3D stereoscopic effects that are on, for example, the family room television. As 3D tech progresses, glasses-free 3D TV may be inevitable, and very young children are more likely to be exposed to that. It's something that 3D tech developers might eventually need to take into consideration.

But what about crossing your eyes? "From doing that, there's definitely no long-term detrimental damage," Borchert finally confirmed for people everywhere.

"But the effect of 3D on young children, we have no idea. For older children, it's not going to hurt them. I can't imagine how this is going to cause any kind of permanent harm to someone who is over four years of age."