Elena Zhukova/UC Regents
Amblyopia, or lazy eye, is the most common cause of vision loss in children. And this condition, which compromises depth perception, can persist into adulthood.
But until recently, treatments for amblyopia hadn’t changed much.
The standard approach relies on an eye patch over the stronger eye to force the brain to rely on the weaker or lazy eye. This works most of the time, but it’s not perfect.
Today, several research teams are adopting a new approach aimed at getting the brain to better use information from both eyes. Several companies have emerged and are working on therapies based on this new angle.
Competition in the brain leaves out the weaker eye
The visual deficits of amblyopic people are not always obvious. They may have difficulty locating objects in space. Problems with depth perception can cause them to squint often. For what? Because there is an invisible competition for visual signals in their brains.
“In all cases of amblyopia, there’s a stronger eye and a weaker eye, and it’s sort of a winner-take-all in the cortex,” says Elizabeth Quinlan, a neuroscientist at the University of Maryland. . She studies people with amblyopia and says their eyes often work very well. Their visual problems come from the signals that the eyes send to the brain. “The cortex learns to ignore the signal from the weaker eye.”
By ignoring the weaker eye, the brain does not merge images from both eyes. As a result, people with amblyopia may have difficulty seeing in 3D.
To try to address this problem, doctors begin treating amblyopic patients at a young age, while their brain pathways are still developing. Children, usually under the age of 7, are often asked to wear an eye patch over their strong eye.
But when the children remove the eye patch, the competition can begin again. For lasting improvement, new therapies must teach the brain to stop suppressing key visual signals from the weaker eye, says neuroscientist Dennis Levi of the University of California, Berkeley.
“You have to get used to paying attention to this information and using it,” says Levi.
Researchers like Levi are working on ways to encourage the two eyes to work together.
Virtual reality trains the brain while children watch cartoons
Companies have also emerged to develop new treatments. One of them is called Luminopia.
“We were very surprised to find that in this day and age, eye patches were the standard of care for such a prevalent disease,” said Scott Xiao, CEO of Luminopia. “It seemed like a very outdated and archaic method,” Xiao says, noting that it can be difficult for parents to persuade their children to wear eye patches. “We decided to develop something better.”
Luminopia therapy involves having children watch videos like Sesame Street, Sponge Bob And Arthur using a virtual reality headset. While kids watch, the headset blocks parts of the screen for each eye.
“So patients need to combine the inputs from the two images to get the full video,” says Xiao.
The company conducted a trial showing that children with amblyopia begin to see better with vision assessments after three months of one-hour sessions performed six days a week. But they have yet to measure improvements in depth perception and long-term effectiveness. The Food and Drug Administration authorized the Luminopia treatment for marketing in 2021. It is available by prescription and with insurance coverage, it has a co-payment of about $50 per month, Luminopia says.
Can you teach an old brain new tricks?
Luminopia treatment is intended for children, not adults. Scientific dogma says that if amblyopic people don’t learn to merge signals from both eyes from a young age, they never will. Some scientists believe that trying to treat adults whose brains have suppressed signals from their weak eyes for decades is a lost cause.
“A lot of people, myself included, fundamentally believe that this is something we can change,” says Eric Gaier, a researcher and ophthalmologist at Boston Children’s Hospital.
Gaier owns a stake in Luminopia and has worked with the company to test its system. He says it’s just one approach to treating people with amblyopia. There are a variety of others being studied that could help adults.
In a recent pilot study, he gave amblyopic adults the drug donepezil, used to treat dementia symptoms like memory loss. Scientists hoped the drug would jumpstart patients’ visual systems, making their brains more receptive to signals from the weak eye. And sure enough, after taking the medicine, some began to improve.
“It was very promising to see that,” Gaier said. Further trials will need to test the drug’s safety and effectiveness for amblyopia, but Gaier is optimistic that adults could one day improve their vision. “There has to be an answer. And there might be new interventions that I and others haven’t thought of yet.”
Anna Marie Yanny is a science journalist in California, where she covers health and environment topics.
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