Vision seekers: giving eyesight to the blind raises questions about how people see

Science News, Nov 22, 2003 by Bruce Bower

For instance, when asked to identify matches between pairs of faces with assorted head angles--posed so that the spacing of facial features appeared to vary--10-year-olds with no prior eye problems performed as poorly as adults with former left-eye cataracts did. Given normal visual development, face processing improves sharply between ages 16 and 18, Mondloch says.

She plans to conduct brain--scan and brain--wave studies of cataract patients to determine their neural responses to faces. The McGill researchers also want to see whether people who had left-eye cataracts removed can be trained to recognize faces solely on the basis of the spacing of eyes and mouths.

Sinha hopes to direct similar studies of Indian youngsters treated for cataracts. Those children will undoubtedly become visually adept in many ways, but they were blind far too long to become face--processing experts, Mondloch suspects. "It's already too late if you receive cataract surgery 2 months after birth," she says.

EYE REVIVAL Even if improvements in vision are marginal for those children surgically thrust into the sighted world after years of blindness, there's room for optimism regarding their adaptation to whatever sight they acquire.

"The kids I've studied show good emotional adjustment after cataract surgery," Sinha says. "It probably helps that adults don't have a lot of expectations about what these children should be able to do as sighted individuals."

Adults who regain their sight after being blind for all or most of their lives are often not so fortunate. Published reports of such cases, which date to 1,000 years ago, often describe an initial elation at being able to see, followed by emotional turmoil, depression, and even suicide.

In his book An Anthropologist On Mars (1995, Knopf), neurologist Oliver Sacks of Albert Einstein College of Medicine in New York recounts the story of Virgil, a man who saw little until having cataract surgery at age 50. Sacks calls Virgil's behavior after cataract removal that of a "mentally blind" person--someone who sees but can't decipher what's out there.

Virgil's perceptual identity, his sense of himself, was tied to experiences that had nothing to do with sight. He often felt torn between first looking at objects or touching them instead, as he had always done. When feeling visually overloaded, he would act as if he were still blind. Often confused, Virgil rapidly sank into depression. About 4 months after his surgery, he died of pneumonia.

Michael G. May has adapted much better to his recovered vision. A stem--cell transplant delivered sight to his right eye in 2001 when he was 43, after 40 years of blindness. Ione Fine of the University of Southern California in Los Angeles and her colleagues describe May's visual progress in the September Nature Neuroscience.

May regards the challenge of learning to see as an exciting new chapter in his life. It helps that he's an outgoing, optimistic person with a supportive spouse, according to Fine.

"Mike certainly sees the world differently than others do," she notes. Two years after his surgery, May still has no intuitive grasp of depth perception. As people walk away from him, he perceives them as literally shrinking in size and has to remind himself that they're farther away than they were before.