- FRIDAY, July 18 (HealthDay News) — Correcting lazy eye in adults
is supposed to be impossible, but researchers report they have been able
to do that — at least partially and temporarily — by beaming magnetic
pulses into the brain.

Someone with lazy eye — ophthalmologists call it amblyopia — has poor
vision because one eye is weaker than the other. Early treatment often has
a child wearing a patch over the strong eye to strengthen the weaker one,
but the problem has been thought to be untreatable in adulthood. Most of
the estimated 6 million Americans with amblyopia are adults.

“We know now that visual loss is caused by poor processing in the
cortex,” said Benjamin Thompson, a postdoctoral fellow in the
ophthalmology department at McGill University in Canada, and a member of
the group reporting on the new method in the July 22 issue of Current
Biology. “Treatment usually addresses the problem with the eye, not
with the cortex.”

The study was prompted in part by research at a number of institutions
showing that changes can occur in the adult brain, which until recently
was thought to be impossible.

The cortex is a vital part of the brain, involved in vision among other
functions. Work by other researchers has shown that transcranial magnetic
stimulation, in which a rapid train of magnetic impulses is delivered to
the brain through a hand-held coil placed on the scalp, has been effective
in stroke rehabilitation and is being tested against depression.

When it was tried on nine adults with amblyopia, 15 minutes of magnetic
stimulation improved the sensitivity of the weaker eye temporarily,
Thompson said. In visual tests, they were able to see finer details than
before the treatment.

“We were surprised by how well it worked,” he said. “Vision in the
amblyopic eye improved for at least 20 minutes after transcranial magnetic
stimulation.”

It was admittedly a small trial, but “one of the issues we were
addressing was whether amblyopia could be treated in adults,” Thompson
said. “The adult brain doesn't have the same capacity for change as in
children.”

There are two ways to exploit the finding, and the McGill group plans
to try both of them, Thomson said. One route is to use multiple bouts of
transcranial stimulation.

“We've only tried a single dose so far in our study,” he said. “Now, we
can look at the effect of repeated doses. In depression, it seems they can
have an effect.”

The other possibility is to use magnetic stimulation to prime the brain
for a rehabilitation program, a training regimen in which adults are asked
to perform a series of visual tasks. Recent studies have indicated that
such a perceptual training program can improve vision in amblyopic
eyes.

“We will also have a parallel project, a training regime with stimuli
to both eyes, higher-contrast stimuli to the amblyopic eye,” Thompson
said. “We hope that repeated exposure will bring improvement.”

The report is one of several indicating that the adult brain has more
capacity for change than had been thought, said Dr. Robert Cykiert, a
clinical associate professor of ophthalmology at New York University.

Lazy eye occurs because the proper connections between the eye and the
cortex do not form early in life, Cykiert explained. “We thought that if
the connections do not form by age 10 or so, it is too late.”

The McGill study indicates otherwise, he noted. “The study has very
preliminary results, but obviously this may lead to other related or
similar treatments that may have a more lasting effect,” Cykiert said.
“What we might be able to do is to allow people with lazy eye to have
treatments that stimulate that part of the brain.”

More information

Amblyopia and its current treatments are described by the National Eye
Institute.