Lazy eye, the most common cause of visual impairment in one eye among children and middle-aged adults, may be linked to a defect in how the brain detects motion, a new study suggests.

Lazy eye, also known as amblyopia, is a condition that involves reduced vision in one eye because that eye and brain are not working together properly. The eye may look normal, but the brain favors the other eye, according to the National Eye Institute. The condition affects 2 percent to 3 percent of all children, and unless treated, will persist into adulthood.

Previous research into the cause of lazy eye focused on visual processing in a part of the brain called the primary visual cortex. But while this research deepened scientists' understanding of the condition, it did not explain issues with motion perception, according to the researchers.

"This study shows that amblyopia results from changes in the brain that extend beyond the primary visual cortex," study researcher J. Anthony Movshon, director of the Center for Neural Science at New York University, said in a statement.

Scientists from NYU examined the middle temporal region of the brain, which has a well-established role in processing information about moving visual objects. To find the role of this brain region in lazy eye, researchers tested the ability of macaque monkeys with and without lazy eye to detect motion.

In the monkeys without lazy eye, the neurons in the temporal region of the brain responded to signals coming from both eyes equally. But in monkeys with lazy eye, the neurons in the brain had a stronger response to the signals coming from the eye not affected by the condition, according to the study.

This shows that this region of the brain is also involved in detecting motion, and plays a role in lazy eye, the researchers said.

While the finding gives scientists a better understanding of the link between motion perception and lazy eye, there may be other regions of the brain that are also affected and remain undiscovered, according to Movshon.

The study is published in the Sept. 8 issue of the Journal of Neuroscience.