Amblyopia is a brain disorder in which vision in one eye does not develop properly. It is the most common cause of permanent visual impairment in childhood, affecting 2 to 3 out of every 100 American children, according to the National Eye Institute. Amblyopia is also the most common cause of one-eye visual impairment among young and middle-age adults.
While amblyopia in children can be successfully treated through occlusion therapy – putting a patch over the “good eye” to force the brain to use the weaker “lazy eye” – few options are available for adults with this condition.
“These new findings are very encouraging because there are currently no accepted treatments for adults with amblyopia,” said study principal investigator Dr. Dennis Levi, UC Berkeley professor and dean of optometry and a researcher at the Helen Wills Neuroscience Institute. “A lot of eye doctors start closing the books on successful treatment after age 8 or so because of the widespread belief that amblyopia can only be reversed during a critical window of development in the visual cortex. If the disorder is not corrected in childhood, the damage was thought to be irreversible.”
But recent studies on perceptual learning, including those authored by Levi and Li, have dispelled the notion that no vision improvements are possible in adult amblyopes. They found that intensive training on a perceptual task, such as getting two horizontal lines aligned, could lead to a 30-40 percent improvement in visual acuity.
In the first experiment, 10 participants played the action video game for a total of 40 hours, two hours at a time, over the course of a month. In a second experiment, three other participants played the non-action video game for the same amount of time. While they were playing video games, participants wore a patch over their good eye.
Both experiments yielded a 30 percent increase in visual acuity, or an average improvement of 1.5 lines on the standard letter chart used by optometrists. In comparison, it can take 120 hours of occlusion therapy to see a one-line improvement on the letter chart in children with amblyopia, the authors said.
Performance was measured after every 10 hours of gaming, the researchers noted, and some subjects started improving earlier than 40 hours.
To verify that the results were specific to video game playing and not due to the use of the eye patch, the researchers conducted a third experiment in which seven participants wore a patch over their good eye for 20 hours during their normal daily activities, such as watching television, reading books and surfing the Internet. At the end of the 20 hours, they showed no improvement on the vision tests. Those same subjects were then asked to wear a patch while playing video games for 40 hours, and when tested, showed the same level of improvement as the other study participants.
Among the 20 study participants, half had strabismic amblyopia, marked by misaligned or crossed eyes. Six had anisometropic amblyopia, in which the two eyes have significantly different prescriptions. Another three had both conditions, and one subject had amblyopia caused by cataracts in one eye.
The study found no significant difference in visual acuity improvement among the different types of amblyopia. However, anisometropic subjects also saw a 50 percent improvement in 3-D depth perception after 40 hours of playing video games.
Li noted that the subjects who started off playing a non-action video game continued to improve after playing the action video game for an additional 40 hours. “It is not clear, yet, when vision improvement might plateau,” he said. “But it’s likely that those who have severe amblyopia will take longer to show improvement, but those patients also have the most room for improvement.”
Li also cautioned that the research on video game therapy for amblyopia is still in its early stages, and that patients should not attempt to “self-treat” their amblyopia. “People definitely need to work with their eye doctors,” he said.