MARTIN, Slovakia (Reuters) - The condition called lazy eye has long been considered untreatable in adults, but a clinic in Slovakia says a treatment does exist, and it’s simple as child’s play - literally.

Lazy eye, or amblyopia, typically occurs in farsighted patients when the brain shuts down data coming from the eye with less clear vision and uses only the healthy eye. People with amblyopia typically do not have three-dimensional vision.

Now the UVEA clinic in Martin, in northern Slovakia, is testing a treatment that uses a pair of virtual reality goggles and a computer game to shake the lazy eye out of its torpor.

“Patients put on the VR goggles that show two different pictures to each eye and start playing a computer game, navigating a spaceship or playing basketball,” said Anders Rustand Holm, a doctor at the clinic

“We can improve sight by forcing the lazy eye to cooperate with the healthy eye. You have to use both eyes to play the game. You’re training them to cooperate,” Holm said.

The usual treatment has been using an eye patch on the stronger eye or blurring its vision with atropine, forcing the amblyopic eye to take over. But it works best on patients younger than six or seven, and most people are first diagnosed when they enter school, when it might be too late.

“People with well established amblyopia had no possibilities until now,” Holm said.

The clinic’s doctors use the Oculus Rift headset, owned by a division of Facebook, and software developed by the U.S. company Vivid Vision.

They have treated some 300 patients with amblyopia since 2015. The average improvement was one line in an eye chart in a month.

They were the first in the world to publish the results of a clinical trial of the treatment, in June in a peer-reviewed journal BMC Ophthalmology.

“I was told that my condition is untreatable. I’ve been in this treatment for a month and my vision has already improved by one line in the eye chart,” said Patrik Turek, a 21-year-old construction worker hoping to eventually lose his semi-rimless metal glasses.

The treatment for previously untreatable condition might get even more accessible in the future.

“At the moment, it’s quite costly - you need a good computer, with good pair of glasses with virtual reality. But this is definitely something that will be possible in the future, when it gets more cost effective. People will be able to buy them themselves and apply this treatment at home,” Holm said.