Relocating central vision
The patients that Emory low vision specialist Susan Primo sees have already exhausted most of their treatment options.
They've completed medication regimens or had surgery to slow advanced age-related macular degeneration (AMD), a leading cause of blindness in the elderly. But still they don't see well.
That's where Primo comes in. She is studying whether behavioral modifications can lead to a change in brain activity to maximize use of remaining vision. "I work with these patients to see what they'd like to do to regain some independence," says Primo, director of Vision and Optical Services, Low Vision at the Emory Eye Center. "Is it reading the mail or the Wall Street Journal? Or maybe, it's driving."
In macular degeneration, the macula—a layer of tissue on the inside back wall of the eyeball—gradually deteriorates. That delicate tissue is responsible for visual acuity, particularly in the center of the retina. Central vision is needed for seeing small and vivid details such as words on a page or the color of a traffic light, which means it is vital for common daily tasks such as reading or driving.;
In more than two decades of working with patients who are visually impaired, Primo realized that people typically use their peripheral vision to compensate for loss in central vision. Studies have shown that people with progressive central vision loss compensate by spontaneously adopting a preferred retinal location (PRL) that takes over responsibility for visual clarity.
But what Primo, along with Georgia Tech psychologist Eric Schumacher, wanted to know was whether using these peripheral regions caused a change in how the brain is organized. Armed with Schumacher's expertise in functional magnetic resonance imaging and Primo's clinical experiences, the researchers did indeed discover continued activity in the part of the brain that maps to the macula. The brain scans of people with AMD who had developed their peripheral vision showed substantially more activity than those of people who had not developed a PRL. Their study appeared in the December 2008 edition of Restorative Neurology and Neuroscience
In a current study, Primo and Schumacher are exploring whether occupational training and biofeedback can help people with AMD focus on using good retinal cells and in turn speed up the brain's reorganization. "Although others have tried to study this reorganization of macular degeneration before, no one, to our knowledge, has tried to influence it," says Primo. "Yet it's important to begin to come up with therapies, treatments, and technology to help patients begin to use their residual vision faster and better than they could before." —Robin Tricoles
