Heard Of Blindsight?

Computer exercise helps stroke victims "see" again

Wed, Apr 01, 2009
Reuters

By Maggie Fox, Health and Science Editor

WASHINGTON - Millie Sauer did not even know she had suffered a stroke until she tried to read a book as she recovered from surgery and saw only a gray blur for part of the page.

Hours or even days had passed since the stroke had damaged part of her brain responsible for vision and Sauer, 69, was far past the point for any effective treatment.

"I was told I would have to live with my situation," Sauer, who lives in Sun City West, Arizona, said in a telephone interview.

But an experimental computer-based program has helped Sauer regain some sight and given her hope of further recovery.

"We were very surprised when we saw the results from our first patients," said Krystel Huxlin of the University of Rochester Eye Institute in New York, who tested the system with seven stroke patients.

"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."

Writing in the Journal of Neuroscience, Huxlin and colleagues said their approach used so-called blindsight -- when a person with vision loss senses something they cannot actually see.

"It is interesting that if you forced them to guess ... they can sometimes guess correctly. This is a phenomenon termed blindsight," Huxlin said.

Sauer and some other patients can drive, shop and live near-normal lives. "I think I have been able to live a pretty fulfilling life," Sauer said.

But it took months of staring at a computer screen to do so.

Strokes damage various parts of the brain and when the visual cortex is affected, the basic machinery involved in sight remains intact. The eye is taking in images -- but the brain is incapable of processing them correctly.

"A lot of neurologists and clinical practitioners are not aware that it is possible to regain vision after stroke," Huxlin said.

Patients with partial paralysis after a stroke are sent to physical therapy and can train new areas of the brain to control movement. Huxlin saw no reason why that could not be done with vision.

The exercise consists of focusing the damaged area of vision at a computer screen. A field of dots appears, moving like a school of fish or a flock of birds in one direction. The patient must decide the direction the dots are moving.

To Sauer, the improvement is subtle. To Huxlin, it is surprisingly substantial.

"The patients can't see the dots, but they're aware that there is something happening that they can't quite see. They might say, 'I know that there's something there, but I can't make any sense of it,'" said Huxlin.

Eventually, they learn to make use of this "blindsight" although it has yet to become vision in the way most people think of it.

She said the success rate went from 50 percent at first, which is what might be expected from random guessing, to 80 or 90 percent. For some of the patients, this meant they could resume driving and shopping, Huxlin said.

-Reuters