Amblyopia, which is known as lazy eye, is a highly visible and obvious condition. But the physical manifestation of the most common cause of vision problems among children the world over is actually a brain disorder. A “lazy eye” is not lazy at all.
Research has shown that amblyopia is a disorder of the brain’s ability to use both eyes together as a team. Amblyopia is an active process due to suppression, or the brain actively ignoring the information coming from one eye. In addition to poor visual acuity, people with this disease have difficulties with depth perception, eye movements related to reading, and visual decision making.
Most often, in amblyopia patients, one eye is better at focusing. Brain retrieves the information from the eye and pushes down the signal coming from the other, ‘lazy’ eye. In a way, it’s better to think of the better eye as a bully, rather than the poorer eye as lazy. As the brain develops its preference for the dominant eye’s input, it alters its connections to the weaker eye.
With diffusion-weighted imaging, which is a brain-scanning method, scientists have mapped three sets of pathways known to carry visual information from the eyes to the brain. In people with amblyopia, water diffusing was seen more easily down the brain’s visual pathways.
A new understanding of the structural effects of amblyopia could help improve treatments for amblyopia and similar vision disorders in which sufferers have trouble judging distance and location of objects in parts of their visual field.
The most common medical response to the lazy eye is to correct the cause, most often the muscular misalignment of the eyes, but sometimes a misshapen lens, through surgery, and put a patch over the amblyope’s strong eye to force the brain to adapt to using the formerly lazy one. But that treatment is usually limited to children.
“You don’t see any adults walking around with patched eyes, because adults’ brains are less plastic, less trainable, and we think the patch approach doesn’t have any effect late in life,” says Rokers, whose group’s work has been funded by the Wisconsin Alumni Research Foundation and the Netherlands Organization for Scientific Research. “But that belief is changing, and this diffusion-weighted imaging approach will help us understand whether, and how much, brain training treatments work.”
It will also aid in the development of new treatments like some ophthalmologists are developing using video games and virtual reality headsets.