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ANN ARBOR,
MI - Infants are not born with normal vision. Over the first
six to nine years of life, children actually learn how to see properly.
If a serious eye condition such as strabismus
(a misalignment of the eye) or amblyopia
(poor vision in one eye from disuse) - both often called 'lazy eye'
- occurs, a child's brain will never learn to see correctly and
vision in the affected eye will be permanently lost if not treated.
Pediatric ophthalmologists
(doctors who are eye specialists) at the Kellogg
Eye Center in the University
of Michigan Health System advise parents on what to look for
to ensure proper eye and vision development for their young children.
According to
Monte Del Monte, M.D., director of U-M Pediatric Ophthalmology at
the Kellogg Eye Center, vision is a skill that children develop.
The brain's learning process requires two things during early childhood:
- The eyes
must be aligned at the same target.
- The target
must be brought into focus on the retina of each eye.
Experts believe
that between four and five percent of children under 12 years old
develop a significant eye problem. Among the serious problems, the
most common is called amblyopia,
which is a failure for the brain to connect properly to one of the
eyes. In other words, it is poor vision in one eye caused by disuse.
Amblyopia most
often occurs when asymmetrical refraction (near-sightedness or far-sightedness)
prevents both eyes from focusing at the same time.
"The brain
sends signals to the eyes to focus. When just one eye comes into
focus and the child sees adequately, the brain stops trying to make
both eyes work together to focus," Del Monte says. "In
that situation, that one eye will always be in focus and its connection
to the brain will develop. The other eye will remain out of focus
throughout childhood and will not develop the needed connections
to the brain."
This type of
amblyopia is the most difficult to diagnose and treat, because there
are no symptoms for parents to see and discuss with their pediatrician.
Frequently, it isn't diagnosed until a child receives routine vision
screenings at school, usually around four, five or six years of
age. At this point, it is often too late to treat.
A second type
of amblyopia occurs when the eyes are misaligned. This is called
strabismus and it can sometimes be noticed by parents. Symptoms
include:
- Eyes that
are not aligned, either cross-eyed or turn outward;
- Eyes that
don't work together to follow a target;
- Eyes that
don't look in the same direction all the time.
If not identified
and treated early, the child will experience double vision for awhile,
until the brain turns off one of the eyes in order to eliminate
the double vision.
 "This
is called suppression. If the same eye is suppressed over a long
period of time, it won't connect to the brain properly, resulting
in permanent loss of vision," says Del Monte, who is also the
Skillman Professor in the U-M departments of Ophthalmology, and
Pediatric & Communicable Diseases.
The last cause
of amblyopia, and the one that is least common, is a blockage of
vision in one eye. This type of amblyopia, called deprivation amblyopia,
may develop because of an eyelid tumor, swelling, or drooping that
covers the eye. It can also result from a problem which blocks the
light path into the eye, such as a scar on the cornea (which is
like a window at the front of the eye) or a cataract or bleeding
within the eye.
Since vision
is developed from birth until a child is between six and nine years
of age and this development requires continuous focused images in
both eyes, if amblyopia develops, the condition must be diagnosed
and treated as early as possible for the best result. Once the child
reaches the age of visual maturity, roughly six to nine years of
age, the brain can no longer make new connections with the eye and
good vision is permanently lost.
Treatment options
depend on the cause of the amblyopia. If the problem is an abnormal
or asymmetrical refraction, then the treatment involves proper glasses
therapy, generally to be worn full time. If the problem is related
to difficulty with alignment of the eyes, then the eyes must be
straightened, either by wearing glasses, a patch on one eye, medicine
in the form of eye drops, or surgery.
A common treatment
for amblyopia involves patching, or occlusion therapy, in which
the child must wear a patch over the strong eye so that the weaker
one can grow stronger through use, according to Del Monte.
In cases of
deprivation amblyopia, the blockage of the light path must be cleared
by raising a drooping eyelid, shrinking an eyelid tumor or removing
a cataract or hemorrhage that is inside the eye.
Del Monte says
that by six or eight weeks of age, a child's eyes should be aligned,
focusing properly, looking in the same direction and tracking together.
If parents suspect these are not happening, they should follow up
with a visit to their pediatrician or an eye specialist for diagnosis
and treatment of the suspected eye problem.
The American
Academy of Ophthalmology and the American Academy of Pediatrics
both have recommendations on when vision screenings should occur.
The first should be at the hospital as part of a newborn baby's
discharge examination. Screenings should also take place in the
doctor's office at two, four and six months of age. Later amblyopia
screenings should take place at three years of age, and each year
after school starts. These can take place at the doctor's office,
with an eye specialist, or at school.
Elizabeth Coffey
is the mother of a lively five-year-old named Alexander.
"He loves
school and he's very smart. He's very mechanical and he can make
anything with blocks. I think he's going to be a scientist someday,"
she says.
Just before
Alexander's third birthday, Coffey noticed one eye was beginning
to cross. Sometimes it was very slight, and other times - usually
toward the end of the day - it would be very noticeable.
"It seemed
that a lot of times, we would notice it when looking at pictures
of Alexander. It would be almost crossed all the way over to his
nose. But, he didn't seem like he had a problem seeing," she
says.
Upon taking
Alexander to an eye specialist, Coffey was surprised when Alexander
couldn't see with one eye covered up.
"He kept
trying to push the little paddle away and he couldn't see the letters
to read them. I was amazed. I had no idea he couldn't see - there
were no other signs that he couldn't see," Coffey remembers.
After Del Monte
diagnosed him with strabismus and amblyopia, Alexander began wearing
eyeglasses and a patch over his good eye. He's also had surgery
to adjust the strength the muscles of his eyes so they would be
properly aligned.
According to
Coffey, Alexander now has 20/20 vision when he wears his glasses,
and he may not need to wear glasses at all in a few years.
"Alexander's
doing great now. He wears his glasses and he is a happy little boy.
If we had waited until he was older, it would have been too late
and we wouldn't have been able to correct the problem," she
says.
For more
information, visit the following Web sites:
U-M Kellogg
Eye Center: Amblyopia
www.kellogg.umich.edu/conditions/pediatric/amblyopia.htm.
U-M Kellogg
Eye Center: Strabismus
www.kellogg.umich.edu/conditions/pediatric/strabismus.htm.
U-M Kellogg
Eye Center: Eye Exams
www.kellogg.umich.edu/conditions/eyeexams/eyeexam.html
National Eye
Institute: Amblyopia
www.nei.nih.gov/health/amblyopia/index.htm
National Eye
Institute: Photos, Images and Videos
www.nei.nih.gov/photo/eye_exam/eye_exam.htm
American Academy
of Pediatrics: Preschool Vision Screening
www.aap.org/advocacy/releases/article2.htm
Written
by Mary Beth Reilly
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