Magnetic Pulses To Brain Help 'Lazy Eye'

About 3 percent of people in the U.S. suffer from amblyopia, or "lazy eye" as it is more commonly known. People with the condition can see out of both eyes, but one eye dominates and the eyes may not work together. Now a team of scientists in Canada has shown that magnetic pulses to the brain may help restore abilities to the weaker eye.

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The standard issue human being comes with a remarkable kind of stereo camera -our eyes. Each one takes an independent picture of the world and our brains put those two pictures together. But that process doesn't work so well for people with amblyopia, or lazy eyes. Their brains can't marry the two independent pictures, and as a consequence the picture from one eye isn't developed properly. Something breaks down in the processing equipment in the brain.

Now, scientists in Canada think they're onto a new strategy for fixing the problem. NPR's Joe Palca has more.

JOE PALCA: About two or three percent of children born in this country suffer from amblyopia. Frequently the condition is caused when one of their eyes is out of alignment when they're born. Surgery can correct the pointing problem but:

Dr. BENJAMIN THOMPSON (Researcher, McGill Vision Research): They still won't recover vision in that eye because, see, the underlying neural processing of information from that eye has developed abnormally.

PALCA: Benjamin Thompson is with McGill Vision Research at the Royal Victoria Hospital in Montreal. It's not that children with amblyopia go blind in one eye.

Dr. THOMPSON: When you cover the good eye, they can see through their amblyopic eye and depending on the depths of amblyopia, they can sometimes see reasonably or hardly at all.

PALCA: Now, remember amblyopia is a brain problem. The eyes work okay; it's the brain that's having trouble processing signals from the eye. Treatment for amblyopia frequently involves wearing a patch over the good eye to force the brain to use the bad eye. That treatment might continue until a child is ten or so.

Dr. THOMPSON: But after that it's thought that really you don't have the ability to change in the brain that would allow you to recover function in the eye.

PALCA: So, to help adult amblyopes Thompson and his colleagues tried a new approach called Transcranial Magnetic Stimulation, or TMS. Basically it involves putting an electrical coil against the scalp.

Dr. THOMPSON: And a very brief magnetic pulse is induced in the coil and that sets off a very brief electrical current in the underlying cortex.

PALCA: Thompson applied a series of pulses called repetitive TMS, or RTMS to the scalps of amblyopes.

Dr. THOMPSON: We could improve the vision in the amblyopic eye after just 15 minutes of RTMS.

PALCA: It's not clear why magnetic stimulation is improving vision and the improvement was modest and it only involved the ability to see contrasting lines, not stereovision. But the improvement did come in adult subjects, showing it may be possible to teach old brains new tricks. The work appears in the journal Current Biology.

Don't get the idea that any revolution in amblyopia treatment is imminent. Lynn Kiorpes is a Vision Researcher at New York University. She points out that the Canadian study involved only nine subjects and only one of the subjects showed substantial improvement. Still, it's possible the effect is real.

Ms. LYNN KIORPES (Vision Researcher, New York University): It is conceivable that this procedure in combination with some other kind of vision training could effect a long-term change.

PALCA: Kiorpes' NYU colleague Anthony Movshon is also skeptical about how useful magnetic pulses will be. He's more impressed with an experimental therapy called perceptual learning, where adult amblyopes are given a kind of visual exercise regimen to stretch their brains. He's not clear how magnetic stimulation would help with that.

Mr. ANTHONY Movshon (Researcher, New York University): It's very hard to imagine that whatever goes in perceptual learning, which is probably a slow cumulative process, can be simulated or mimicked by simply whacking the brain with a few magnetic pulses.

PALCA: But Eric Wassermann sees more promise in the Canadian results. Wassermann is at the Neurology Institute at the National Institutes of Health. He's been working with magnetic brain stimulation for years. He says it can wake up portions of the brain that for some reason have become dormant.

Dr. ERIC WASSERMANN (Neurologist, Neurology Institute, National Institutes of Health): It's a useful tool for this sort of demonstration, because it's very safe and we don't have to open people's heads in order to apply it.

PALCA: He says magnetic stimulation may yet become a valuable tool for treating amblyopia.

Joe Palca, NPR News, Washington.

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