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Blind man's restored vision offers new insights

Forty-three years after he was blinded by a childhood accident, Michael May had his sight restored by experimental stem cell surgery.

His one good eye is optically almost perfect, and he can perceive color and objects in motion. But three years after his surgery, he still can't easily recognize faces or grasp much of the world he sees in its full three dimensions.

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Scientists writing in the journal Nature Neuroscience this week say May's case has given them new insights into how the brain processes visual signals and how early blindness can shut down portions of that processing work forever.

"What we've found is that different areas of the brain have totally different types of plasticity beyond the first three years of age," said Ione Fine. Deprived of visual stimulation, some "just spiral out of control and stop responding. Other parts don't care and just stay until the 'lights' go back on."

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Fine, a neuroscientist at the University of Southern California, is the lead author in a study of May's case published this week in the journal's online edition. The work was done at the University of California at San Diego.

The scientists' conclusion is that portions of the brain that process color and motion are "hard-wired" by evolution, or at least learned early and fixed in a child's brain sometime before the age of 3.

But those areas dedicated to recognizing faces and processing complex objects in three-dimensional space remain "plastic" -- probably to allow us to continue to learn and adapt in an environment in which we are continually stimulated by people and things that are always changing.

But in May's brain, the visual stimulation ended at age 3, and that portion of his perception withered and died.

May has little or no memory of his accident. He has been told that he found a bottle of powdered calcium carbide lantern fuel in his family's garage one day. The chemical fuel got wet and exploded. The burns destroyed his left eye and damaged the surface of his right eye, leaving it sensitive only to light and dark.

Doctors tried three times to replace his scarred cornea with transplants. They all failed because the surrounding eye tissue was too damaged to support them.

But he was adapting to blindness well. He learned Braille, and how to navigate with a cane and a dog. In 1979, he earned a master's degree at the Johns Hopkins University School for Advanced International Studies and took a job with the CIA. He married and had two sons, now 9 and 11.

He learned to play flag football, soccer and pingpong by sound. He became a downhill ski racer, using the wind, verbal cues from a sighted guide and the sound of the guide's skis on snow to steer him down the hill. He even skied a demonstration run at the 1984 Olympics in Sarajevo.

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Today he owns Sendero Group, a Davis, Calif., firm that develops and markets electronic aids for the blind.

So when May learned of experimental surgery that might restore his sight, he hesitated. He was doing fine without sight, and he worried about the medical risks. But in the end, he said yes. "If you have the opportunity to go to the moon, you don't turn it down, because it might not come around again," he said.

Doctors at St. Mary's Hospital in San Francisco first transplanted a ring of donated epithelial stem cells to his eye. Epithelial cells provide a nourishing base and a protective cover for the cornea. Four months later, when the stem cells were well-established, doctors replaced May's cornea with one from a cadaver.

And like a movie cliche, when the bandages came off he could see doctors in white coats, medical instruments -- "this big whoosh of information, a giant torrent."

Past experience had taught doctors that good visual perception requires more than a sound eyeball. It also demands complex signal processing in the brain. And when those processing centers go unused from childhood, something stops working.

Just what, however, has never been thoroughly studied because sight restoration after childhood blindness is exceedingly rare. Only about 20 cases have ever been reported.

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Fine and her colleagues eagerly launched a battery of studies, from visual acuity tests to brain scans, called functional magnetic resonance imaging.

They found that May's eye should have 20-40 vision -- good enough to get a driver's license. But he also has amblyopia -- low visual acuity, or a reduced ability to see fine detail. That was expected. Nerves had degenerated and probably won't improve.

But May's deficits go beyond that, Fine said. While he can recognize simple shapes, he is unable to interpret the two-dimensional images on his retina as three-dimensional objects.

"He sees the world the way abstract painters paint it," Fine said.

Fine and her colleagues found that the areas of the brain that burst with activity when sighted people process complex, three-dimensional objects stay stubbornly dark in May's brain scans.

The same was true with the area that handles face recognition. "You would think I would be better at face recognition by [age] 3," he said. "Somehow, that part of my capability did not come back."

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While May can see faces well enough, his brain cannot connect the complete pattern to the individual person. Fine compares it to most people's perception of sheep. Except to shepherds, they all look alike.

"For Mike," Fine said, "we all look like sheep."

He's doing better by memorizing such details as hair color, the shape of an eyebrow. And he's getting faster at making the connections. But it's slow.

Similarly, he said, "I don't get perspective." The walls of a long corridor don't appear to converge for him as they do for sighted people. His depth perception is poor.

"In my mind, a hallway or a road is a certain width, and that width is based on my impression tactilely," he said.

Other portions of May's visual processing centers work just fine. "I'm good at color," he said. He also still has good motion processing.

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When May was presented with a 3-D image of a cube on a computer screen, he saw what he described as "a square with lines." But when Fine put the cube into motion, May immediately saw it in three dimensions.

"It was if he'd put on 3-D spectacles," Fine said. "It was a creepy moment, just incredible. I had not been expecting that."

For his part, May said he is "pleasantly surprised" by how little vision has helped him function. He does fine without it, as he always has. And some of what he sees frankly disturbs him. He was appalled by his first sight of homeless people lying on the sidewalk.

But he has also delighted in other revelations. "I saw dust floating in the air one time, and I was just completely blown away," he said. How could something he couldn't feel be so visually noticeable?

He's also been astonished by people -- their infinite variety and appearance. Especially women.

"There are so many women," he said, "lots of times half-clad. And I think, 'My God, the world is a beautiful place.'"


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