James Cameron's Avatar is a rare visual treat but the 3D movie has had some unexpected side-effects, including eye ache, dizziness, nausea and even vomiting, among a small group of audiences.
According to Chinese media, a middle-aged lady in Hangzhou, Zhejiang province, who watched the movie, went to hospital afterwards, feeling so dizzy she could hardly stand. Another viewer said in an Internet posting he felt acute eye ache and had blurred vision after watching the film. Doctors found he had acute glaucoma.
Wang Wei, a senior doctor in the ophthalmic department at the China-Japan Friendship Hospital, says most people can rest assured that watching a 3D movie is not dangerous.
"Only 3-5 percent of the population are vulnerable to glaucoma," he says. "For other people, they might just experience eye fatigue."
3D movies try to create a 3D feeling with two overlapping 2D images, quite different from the natural way eyes perceive 3D.
"Therefore people need to constantly adjust their eye structure, but also need to make a mental effort to put the two images together and treat it as real 3D," Wang explains.
Meanwhile, the eyes are more likely to get tired because the two parts of the 3D glasses allow only half of the ordinary amount of light into the eyes.
The intriguing plot of Avatar requires people to focus their attention much more than usual, for about 160 minutes, making the experience more demanding for the eyes.
"The feeling of eye fatigue is almost the same as that of glaucoma: headache, an eye swelling, nausea, and even vomiting," Wang says. "But most people will get better after an hour or two in the case of ordinary eye fatigue. If the symptoms are prolonged, one needs to see a doctor."
The worst situation for glaucoma patients, if they go without proper treatment, is loss of sight. Emotions such as anger, sorrow and excitement, can all induce glaucoma, according to the doctor.
Wang describes the group of people most vulnerable to glaucoma as those who are over 40 years old, with a family history of glaucoma. He recommends these people take medicine before watching 3D Avatar, or watch the 2D version instead.
Wang says people with other eye problems, such as a squint and short- or long-sightedness are more likely to get tired after watching 3D movies. So are people with relatively weak physical conditions, those who are more sensitive, and the elderly. But these people can recover after some rest. There is no need for them to see a doctor.
If people feel dizzy watching Avatar, Wang suggests they should take off their 3D glasses and shut their eyes for a while, or leave the environment when the symptoms get serious. It is better to sit further away from the screen.
Applying eyedrops might be a good idea, because it alleviates dry eye, and eye fatigue. Eating snacks or talking with your partner during the movie is not a bad idea either: It distracts the attention briefly, and will help ease the pressure on your eyes.