Researchers Measure Retinal Function Through Vision Map of the Brain

October 19, 2012

Thanks to research recently reported in the journal Current Biology, a doctor may soon be able to tell which parts of a person’s retina are functioning by looking at his or her brain.

Vision occurs through a connection between the retina and the brain’s visual cortex. The retina — the thin, square-inch piece of tissue lining the back of the eye — converts the light entering the eye into electrical signals, which are sent through the optic nerve to the brain’s visual cortex. The brain then interprets those electrical signals to create the images we see.

Researchers from the Perelman School of Medicine at the University of Pennsylvania recently mapped out where information from specific areas of the retina is routed in the visual cortex. They discovered, for example, that input from the central retina maps to one region of the brain whereas information from the peripheral retina maps to another.

One short-term benefit of this vision map is the ability of doctors to accurately determine which areas of the retina are functioning without the patient having to undergo vision tests. Such tests can be difficult to administer to people with retinal diseases who have low vision or can’t keep their eyes from moving during an eye exam.

The map will also help measure the effect of a treatment or change in vision.

“Suppose you have a treatment – for example, a gene therapy – that is applied to just a portion of the retina. Our technique tells us precisely where to look in the brain to determine if that treatment has had an effect,” says Dr. Geoff Aguirre, a lead investigator for the study.

Long-term, this “retinotopic” map will help researchers develop and implement neural prostheses — devices that restore vision by bypassing the eye and connecting directly to the visual cortex.

“If we want to stimulate the brain directly to restore sight, the anatomical map tells us where and how to position the stimulator,” explains Dr. Aguirre.

While its retinal application may be new, vision mapping is not. In 1918, Sir Gordon Holmes, a World War I neurologist, created the first, albeit crude, version of a vision map by connecting soldiers’ blind spots to missile wounds to their brains.