Therapy Restores Field of Vision

Brain’s ability to rewire could be the key

by Kayt Sukel

December 31, 2007

In 2005, Robert Hobbs suffered a stroke that blocked blood flow to parts of his brain and affected his speech, memory and vision.

“Mostly it was an effect on my field of vision,” says Hobbs, 66, of Miami Springs, Fla. “Almost every adult has taken a vision field test, where you stare at a focal point on a machine and respond to lights coming up in your periphery. I couldn’t see the lights on either side, or at least couldn’t see very many of them.” This loss also took away Hobbs’ reading ability, which meant he had to leave his job as a shift supervisor at an Associated Press news bureau.

To help stem the loss, Hobbs started visual restoration therapy (VRT) in January 2006. VRT was developed by Bernhard Sabel at the University of Magdeburg, Germany, and is now marketed by the company he helped found, NovaVision.

Patients do a form of computer-assisted therapy at home for 20 to 30 minutes per day for six months. They sit a specific distance from the computer, with the head placed in a chin support, and click a mouse in response to stimuli that are flashed on the computer screen in the visual field’s border zone, the line between where people can and cannot detect visual information. To date, the therapy has had promising results in improving visual field deficits.

Using ‘replacement’ neurons

Scientists suggest that the brain’s neuroplasticity, or ability to rewire itself after injury to compensate for functional losses, is behind VRT’s success. After a stroke or other injury to the visual areas of the brain, some neurons will not recover. But, researchers hypothesize, there is a backup system of sorts, where neurons next to the injured location can take over lost function if they are stimulated in the right way.

“It’s a training-type therapy,” says Randolph S. Marshall, professor of neurology at the Columbia University Medical Center. “With patients who have a hemiparesis, or weakness on one side, they will practice specific tasks like reaching for a glass or opening and closing the [weaker] hand. That mass practice for a targeted task seems to induce this training-related neuroplasticity. So it’s sort of the same thing for the visual system and stimulating the brain areas related to visual field.”

In a functional magnetic resonance imaging (fMRI) study published in the August 15, 2007, issue of Neurorehabilitation and Neural Repair, Marshall and his colleagues found that the brain did register changes for six patients who were imaged while detecting stimuli across the visual field, both before and one month after starting VRT.

“As patients engaged in this therapy, the way the brain reacted to detecting stimuli in the visual border zone changed,” Marshall says. “There were specific increases in activity in visually relevant areas of the brain happening when they detected stimuli in the trained area versus an untrained one.”

Marshall suggests that the images show the way the brain reorganized itself in response to the visual training. This finding also correlated with improvement to visual processing speed or in the participant’s time to respond to stimuli. On average, VRT widens the blind spot in patients by approximately 5 degrees.

“It sounds like a small amount but it is the difference between half of an 8.5 by 11 sheet [and] a whole piece of paper,” says Marshall. In addition, patients have reported subjective improvements in visual processing, reading and concentration.

Some neuroscientists have been critical of VRT, arguing that eye movements could be accounting for the good results. Marshall agrees that there could be a problem with the data, and he and his colleagues are now running studies to control for eye movements as well as to measure some of the reported subjective good effects of the therapy.

As for Hobbs, after one six-month treatment and a follow-up three-month treatment, he can read again. “I’m probably 60 to 70 percent back to the reading speed I had before I left work,” he says. And though Hobbs says he did not experience any increase in attention or mobility, he’s happy with the results.

“Reading is the biggest thing,” he says. “Reading is everything.”