WASHINGTON (AP) -- Newborns have incredibly poor eyesight that
depends on brain stimulation to sharpen. Now a study suggests
infants' brains are so flexible that just an hour of visual
stimulation can jump-start that process.
A healthy adult's vision is about 40 times better than a
newborn's. That's one reason baby mobiles are sold in sharply
contrasting patterns -- those are easiest for infants to spot.
Over the first six months of life, infants' vision improves
fivefold as their brains are stimulated to establish the neural
network necessary to see.
The question is how much visual stimulation a baby needs.
Daphne Maurer, a vision researcher at Canada's McMaster
University, studied 28 babies born with severe cataracts. They
could distinguish between light and dark but nothing else.
The cataracts were removed between 1 week and 9 months of age.
Then, the hour they were fitted with artificial lenses to finally
process light, Maurer began testing their vision. She used cards
with black and white stripes of varying sizes. Babies look away
from the cards when the stripe is too small for them to see,
allowing visual measurement.
Right after surgery, the babies had the poor vision of newborns.
But after as little as one hour of visual stimulation, these
sight-deprived infants could see one stripe better. It doesn't
sound like a huge improvement, but actually normal newborns, used
to gradual visual stimulation, take a month to improve that much,
Maurer reports Friday in the journal Science.
"It shows us that the nervous system is wired in such a way
that it can respond quickly to visual input," Maurer said.
Over the next month, the cataract babies' vision still lagged
behind normal babies, but their brains adjusted so fast that they
cut the gap in half.
Babies who had very early surgery recovered best, because the
brain is most flexible in early infancy, Maurer said.
The study "demonstrates the amazing plasticity of the young
human brain, and underscores the importance of complete, balanced
early sensory input," wrote Ruxandra Sireteanu of Germany's Max
Planck Institute for Brain Research in analyzing the study.
Congenital cataracts are very rare, occurring in one in 10,000
births. But the findings are applicable to other vision problems,
suggesting babies with signs of trouble need prompt examination,
But if eye trouble is discovered late, "don't give up," she
added. "The effectiveness of any therapeutic intervention is going
to be harder, but there's some neural plasticity even in us old