A Canadian-led study has found that playing video games with both eyes can dramatically improve vision in adults with lazy eye — a condition thought to be all but untreatable in adults.

Lazy eye, known to doctors as amblyopia, is a problem in which a person sees better in one eye than the other and the brain effectively turns off the weaker eye. It affects up to three per cent of the population. People with lazy eye can't see in 3D and can't judge distances as effectively as people with normal vision because those tasks require the use of both eyes at the same time.

In children, vision in the weaker eye can sometimes be improved by covering the stronger eye with a patch and forcing the brain to use the weaker eye.

But up until now, no treatment, including that one, has been effective in adults.

The new treatment developed by an international research team headed by Robert Hess, director of the opthalmalogy research department at McGill University and the Research Institute of the McGill University Health Centre in Montreal, significantly improves the vision in the weaker eye of someone with lazy eye in just a few weeks.

'Surprisingly quick' results

"It's relatively quick, surprisingly quick," said Hess. "More importantly, in a majority of cases, they get back their stereoscopic or their 3D vision."

That may mean being able to watch 3D movies for the first time.

For a long time, scientists thought lazy eye in adults wasn't treatable because adult brains are too set in their ways and can't learn to use the lazy eye.

But recent scientific evidence has suggested that isn't the problem, Hess said. Instead, experiments show that what is probably happening is that the stronger eye suppresses the communication between the weaker eye and the brain. The greater the contrast in the image seen by the stronger eye, the more it suppresses the signal from the weaker eye.

The new treatment involves setting up the video game of Tetris so it can only be played effectively using both eyes. The game involves rotating puzzle pieces as they fall so that they interlock with other puzzle pieces sitting at the bottom of the screen. The researchers split the image between the eyepieces of a pair of head-mounted video goggles so that one eye could only see the falling pieces and the other eye could only see the pieces sitting at the bottom of the screen. They also adjusted the contrast in each eye so that at first, there was very little contrast in the image seen by the stronger eye.

After playing Tetris that way for an hour a day for two weeks, nine adults with lazy eye showed a big improvement in the vision of the weaker eye and in their 3D depth perception, the researchers reported in a paper published this week in the journal Current Biology.

A comparison group of nine adults who played the game using their weaker eye while their stronger eye was patched showed some improvement in their weaker eye. But the vision in the weaker eye and their 3D vision both improved much more dramatically when they too started started playing the game with the image split across both eyes.

Other games could work

"What we have to do is to get the two eyes working together so one eye doesn't suppress the other eye," Hess said. He added that there's nothing special about the Tetris game, and any other visually intensive game or activity that forces the use of both eyes should also be effective.

The adult treatment appears to work much more quickly than patching, which typically requires the child to wear a patch for three to six hours a day for six months to a year before improvements are seen in the weaker eye, Hess said. He added that children whose eyes were patched generally never learn to use their eyes together, and the weaker eye tends to regress over time.

The researchers are scheduled to test the video game treatment in children in a clinical trial across North America later this year.

"What our real interest is in is seeing if can replace the patching that's used in children with something a little more fun and enjoyable that might potentially be more effective."

The study was funded by the Canadian Institutes of Health Research.