'Lazy eye' could change brain wiring

The most common cause of vision problems in children, popularly known as the "lazy eye", may actually be physical manifestation of a brain disorder linked to changes in its connection to the weaker eye, a new study says.

Lazy eye - amblyopia - is a condition in children when vision does not develop properly in one eye.

"Most often in amblyopia patients, one eye is better at focusing," said one of the researchers Bas Rokers, psychology professor at University of Wisconsin-Madison in the US.

"The brain prefers the information from that eye, and pushes down the signal coming from the other, 'lazy' eye. In a way, it is better to think of the better eye as a bully, rather than the poorer eye as lazy," Rokers pointed out.

As the brain develops its preference for the dominant eye's input, it alters its connections to the weaker eye, the study said.

"If you continually have that bullying happening, that changes the signals coming from the lazy eye," Rokers pointed out.

Using a brain scanning method called diffusion-weighted imaging, the researchers mapped the pathways known to carry visual information from the eyes to the brain.

In people with amblyopia, the researchers saw water diffusing more easily down the brain's visual pathways.

"What we think may be happening in amblyopia is that the conductive sheath around neurons becomes thinner," Rokers said.

"In order to conduct information from one location to another, neurons have a sheath of material called myelin around them to insulate and speed up processing. When the myelin is thinner, there is less of it in the way and the water diffuses more easily," Rokers said.

This understanding of the structural effects of amblyopia may 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 findings were published in the journal Vision Research.