• Health

Where Blindness is Epidemic

4 minute read
Carolyn Sayre

Neuroscientists have long been convinced that the first few years of life are a crucial period for brain development–a time when connections between neurons are being forged at a prodigious rate as a baby learns to make sense of the external world. Interfere with that process, and you can cause permanent, irrevocable damage. If a child is born blind, for example, it’s pretty much over by age 6. You can fix the eyes, and they might be able to perceive light and dark. Without the right visual circuitry in place, though, there’s no way to form images–the essence of true sight.

But then there’s the patient known as S.R.D. Discovered by researchers four years ago in Ahmedabad, India, she was a 32-year-old, dirt-poor maid who had been born with severe cataracts. They were removed surgically when she was 12–and within a year, despite what neuroscientific dogma would have predicted, S.R.D. learned to see. Her case, described in the December issue of Psychological Science, is forcing scientists to rethink their long-held beliefs about vision. “There is a critical period for perfect acuity,” says Pawan Sinha, associate professor of neuroscience at M.I.T. and a co-author of the paper. “But there is not a critical period for learning to do complex visual tasks.”

This surprising insight had its genesis in 2002 when Sinha traveled to his native India –where nearly half a million children suffer from blindness. Many of these cases would have been preventable with the proper medical care, and, says Sinha, “I wanted to help the children get treatment.” So with funding from the National Institutes of Health, he launched Project Prakash (it means “light” in Sanskrit), a humanitarian initiative to help expand eye care in India.

He had little hope, though, of restoring vision to children who were past the critical development period. While research with humans has been very limited, experiments with animals have shown that if you place a normal kitten, for example, in a completely dark chamber immediately after birth, the kitten will become irrevocably blind. As a result, doctors in developing nations are often reluctant to perform surgeries like cataract removals on children. The risks–infection, mostly–outweigh the meager rewards.

Evidently, though, nobody told the surgeons who operated on S.R.D. And as Sinha and his colleagues discovered, it’s a good thing. Even though S.R.D.’s visual acuity topped out at 20/200–considered legally blind in the U.S.–her brain had, in defiance of theory, learned to interpret visual information. One year after surgery, she could recognize her family’s faces and identify objects. And that’s a very big deal. Dr. Suma Ganesh, a pediatric ophthalmologist at the Dr. Shroff’s Charity Eye Hospital in Old Delhi, India, used to believe that operating on blind children past the critical period was hopeless. But Project Prakash showed her that just isn’t the case. “Even if a blind kid, after an operation, manages to see up to three meters, it makes a big difference,” Ganesh says.

Important as the project has been to neuroscience, says Yuri Ostrovsky, a graduate student at M.I.T. and lead author of the paper, “the best thing about it is the humanitarian aspect.” Project Prakash has funded about half a dozen mobile eye camps–teams of ophthalmologists that travel to remote areas of the country and provide eye care. The concept itself isn’t new, but unlike other camps, these are aimed just at children.

Still, the science is remarkable. Since hearing S.R.D.’s story, the researchers have analyzed a total of 14 children and one adult at the eye hospital. All of them have shown significant improvement in less than a year. While most were treated surgically, the adult–a 29-year-old man with congenital aphakia (an eye missing its lens)–just needed a pair of glasses. Eighteen months later, he was able to see.

Although the results are undeniable, it’s still unclear what’s going on in the patients’ brains. The researchers will start to explore this question next summer by taking pictures of the brain before and after surgery using functional magnetic resonance imaging (fMRI) scanners. Since the brain devotes roughly 35% of its power to vision, they hypothesize that when this sense is compromised, others, like smell and touch, take over the visual-processing circuits. After surgery, they suspect, the sense of sight reclaims its territory inside the brain.

For S.R.D., alas, the recovery that neuroscientists had deemed impossible was also relatively short-lived. A few months ago, she died in a traffic accident–while taking her blind 9-year-old daughter to an eye clinic.

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