July 7, 2010
3D TV Not Damaging To Your Eyes
Watching 3D television under normal conditions is unlikely to be damaging to the human visual system, scientists from The Vision Centre say.
Commenting on possible health risks raised by some experts with the advent of 3D television, Professor Colin Clifford of The Vision Centre and The University of Sydney, an authority on how the brain interprets the visual signals from the eyes, says it is very unlikely that 3DTV could cause any long-term harm, provided people only watched it for a few hours a day.
"The concern about 3DTV originates with the development, a couple of years ago of virtual reality goggles, which have tiny screens right in front of both eyes which present a slightly different image to each eye," Prof. Clifford explains.
"When we look at an object in depth, two things are yoked together "“ the convergence of our eyes when they point at the object, and the curvature of their lenses. The brain adjusts both of these to focus on close objects and sense the depth of what it sees.
"For objects viewed beyond reading distance, however, the eyes are pretty much pointing in parallel and very little adjustment is required to see things in depth."
As 3DTV is usually watched from a longer distance it is unlikely to affect how the eyes and brain perceive depth of field "“ although Prof. Clifford adds that there has so far been little research worldwide into the effects of 3DTV as yet.
"The human visual system responds to a great many different cues in order to interpret the depth of what it is seeing, so it is not likely to be confused by a single cue "“ a 3D picture which is in fact being projected on a flat screen," he says.
These cues are all tricks which the visual system uses to interpret and deal with depth of field "“ and there are so many of them that it does not matter if one or two are receiving confusing signals, as the brain manages to cross-check and come up with the best answer.
With the VR goggles, however, different signals were being sent to each eye and as a result many of the depth perception cues were conflicting with one another, potentially confusing the brain's processing system.
This would not happen with 3DTV provided it was watched from a normal viewing distance of two or three meters and for a normal viewing time, he says.
"In actual fact two-dimensional TV creates more of a conflict for our visual system than 3DTV, because we have to interpret a 3D image out of a flat screen, whereas 3DTV is just giving us a 3D picture.
Prof Clifford adds the good news is that people who can't afford a 3D television can create their own by watching an ordinary TV with a hand over one eye. "By covering the second eye, you lose the cue from that eye that tells you the screen is in fact flat, and so the image appears more in-depth and realistic. You could say it's a kind of poor man's 3DTV."
However, he adds, it is a good idea not to watch any sort of television "“ 2D or 3D "“ to excess, and always from a sensible viewing distance. "One should be particularly careful about the number of hours young children are exposed to, as their whole visual system, brain and eyes is developing, and the way they sense depth is being laid down. There is a risk that by watching too much TV children could train their visual system in a way where it might interpret what they see in the normal environment incorrectly."
The Vision Centre is funded by the Australian Research Council as the ARC Centre of Excellence in Vision Science.
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