‘Not (3-D TV) tonight, dear; I have a headache’

Most 3-D display technology, whether in the theater or at home, requires viewers to wear electronic glasses that are timed to open and close rapidly. A slightly different image is projected to each eye, and from that difference, the brain creates the illusion of depth.

However, our brains process visual information in many different ways, and human depth perception is a very complicated business. The brain uses 10 different cues to figure out the distance of an object. One if them is parallax, which is used by most 3-D TVs. For 3-D to work, the brain must reject several of the other cues in favor of parallax.

When viewing 3-D is over, the brain is still rejecting those depth perception cues. It takes it time to return to normal. Some people snap out of it immediately, while others take hours to recover. This condition, known as “binocular dysphoria,” is a price humans must pay for cheating their brain into believing the illusion of 3-D TV.

With movies, most less than two hours in length, binocular dysphoria has not been a huge issue (although there have been a few reported cases). However, with sustained 3-D viewing for hours in the home, it could be. As of now we don’t know for sure, because not one of the TV manufacturers has done any health or safety testing on the issue.

Doctors, however, say that headaches and visual disturbance are likely with many viewers of 3-D content; we just don’t know how many yet.

Dr. Michael Rosenberg, an ophthalmology professor at the Northwestern University Feinberg School of Medicine in Chicago, said there are many people with very minor eye problems — a minor muscle imbalance, for example — which the brain deals naturally with under normal circumstances.

However, he said, when watching 3-D content, these people are confronted with an entirely new sensory experience. “That translates into greater mental effort, making it easier to get a headache,” he said.

A recent study by the University of California, Berkeley, concluded that 3-D can cause headaches and blurred vision. Researchers attributed this to viewers focusing on the foreground and distance simultaneously.

ABC News blogger Mike Pesce predicted that one of two things will happen with the recent interest in 3-D technology for the home: Either the fad will quickly disappear from the market, or we’ll soon see the biggest class-action lawsuit in history as millions realize that 3-D TV permanently ruined their depth perception.