People who go partially blind after a stroke may regain some vision after doing a set of visual exercises on a computer for several months, researchers say.

"We were very surprised when we saw the results from our first patients," said Prof. Krystel Huxlin, the neuroscientist who led the study of seven patients at the University of Rochester Eye Institute, in a news release issued by the university's medical centre.

"This is a type of brain damage that clinicians and scientists have long believed you simply can't recover from. It's devastating, and patients are usually sent home to somehow deal with it the best they can."

Huxlin and her colleagues studied four women and three men, the youngest of whom were in their 30 and the oldest in their 80s, who had all had a stroke anywhere from eight to 40 months before the study began.

Five of the subjects completed the study, the results of which appear in Wednesday's issue of the Journal of Neuroscience, and came out with "significantly improved vision," the scientists said in the news release.

The participants were all people who had suffered a stroke that damaged part of the brain know as the primary visual cortex, which passes visual information along to other areas of the brain that process it.

Such people often have trouble reading, driving or navigating in stores without bumping into people or objects. In designing the experiment, the researchers focused on motion perception since that is the aspect of vision critical for such everyday tasks, the news release said.

Follow the dots

Despite suffering a stroke, the patients' eyes still took in visual information, but their damaged brains couldn't make sense of it.

The researchers aimed to build on the patients' "blindsight" by recruiting healthy regions of the brain to improve vision. Specifically, the aim was to stimulate the healthy middle temporal region of the brain so extensively that it could take on some of the tasks normally handled by the damaged visual cortex.

"Can we train those brain regions so hard and stimulate the brain to such a degree that this visual information is brought to consciousness, so the person is aware of what they're seeing?" Huxlin asked.

Study participants were trained to stare at a computer screen on which a group of about 100 small dots would appear that moved like a flock of birds in one direction and then disappeared. The subjects had to decide whether the dots were moving left or right.

Even though patients couldn't see the dots per se, they were aware that there was something happening that they couldn't quite see, Huxlin said.

Over time, the subjects learned to make their blindsight visible. As their brains learned to "see" a new area, their success rate of choosing the correct direction improved from 50 per cent initially (about what would be expected from random guessing) to 90 per cent — enough to resume driving, shopping or exercise for some patients.

As patients improved, researchers moved the dots farther and farther into what was the patient's blind area, as a way to challenge the brain, to coax it to see a new area, the news release said.

"Basically, it's exercising the visual part of the brain every day," said Huxlin. "It's very hard work, very grueling. By forcing patients to choose, you're helping the brain re-develop."

Patients did about 300 tests at a time, equivalent to spending about 15 to 30 minutes in front of a computer once or twice a day, every day, for nine to 18 months.

The research was funded by Research to Prevent Blindness, the Pfeiffer Foundation, the Schmitt Foundation and the U.S. National Eye Institute.