commonly referred to as crossed or wandering eyes, occurs when one or both
eyes turns in or out, up or down. The condition is caused by the brain's
inability to coordinate both eyes simultaneously. The brain is the master
control center of vision, and somewhere early in a child's visual development,
the brain failed to develop "binocularity," or the ability to use
both eyes at the same time. The condition usually develops before a
child is two but can occur as late as age six. It is important
that strabismus receive prompt treatment. Children do not outgrow
crossed eyes, and the condition can worsen over time. Children with
strabismus may develop additional complications with amblyopia, or "lazy"
eye. (Note: It is common to see infants younger than three months
cross their eyes as they are learning how to team and coordinate their eye
movements. This is normal and not a condition of true crossed eyes.)
in which the misaligned eye turns in or out is divided into two categories:
esotropia ("crossed" eye) means an eye turns in towards the nose,
and exotropia ("wandering" eye) means an eye turns out away from the
nose. In addition, the eye turn may be constant or happen only at times, such
as when the child is tired; it may be the same eye which always turns, or the
left and right eyes may turn alternately. The child's eye may turn only
when he is looking at objects close up, or it may turn when looking both near
The degree of eye turn may be so great that it is readily noticeable, or
slight enough that parents may fail to recognize there's a problem.
the brain has not learned to align the eyes and use them together, each eye
aims independently of the other. In other words, both eyes do not point
at the same place at the same time. When each eye is looking at a
different place, the brain receives two different "pictures." This
would normally result in double vision. However, these children's brains learn
to protect themselves from seeing double by suppressing, or "turning
off" the crossed eye. The brain refuses to receive the visual input from
the turned eye; children with a crossed or wandering eye only see out of one
eye at a time.
Suppression is the brain's learned adaptation that protects children from
double vision, but it also causes them to lose depth perception, or the
ability to judge distance. Children with strabismus do not see a
three-dimensional world. Instead, their world appears much flatter without
depth and distance judgments. With the loss of spatial judgment, children with
strabismus are generally more clumsy and are ten times more prone to accidents
because of their compromised visual system.
children and adults can develop a crossed eye after a head injury, stroke, or
as the result of some diseases. When this happens and the onset of strabismus
is later in life, these older children and adults will usually experience
double vision. This is because by age of six the brain is already
"wired" to use both eyes together and therefore can't ignore or
"turn off" the image being received from the turned eye.
types of strabismic conditions are treated differently. For example, glasses
will nearly always be prescribed for esotropia. The glasses help relax the
crossed eye that is turning in too far, allowing it to aim straighter.
In very mild cases of crossed eyes this may be enough to correct the problem,
but usually additional treatment is required. There are two different
approaches to the treatment of strabismus: surgery and therapy.
The Surgery Myth
or eye surgeons, usually recommend surgery to correct strabismus.
However, strabismic surgery has some very real limitations: it will improve
the eye's appearance, but rarely does it do anything to improve vision. The
situation cannot be overstated: surgery for crossed or wandering eyes is by
enlarge a cosmetic consideration with little or no affect on the eye's visual
function. In fact, the nerve damage and scar tissue that result may
permanently reduce the child's chances of achieving normal two-eyed vision
later on through therapeutic remediation.
often have common misconceptions about eye surgery. One of the most frequent
misconceptions is that strabismus is caused by "weak" eye muscles.
This is simply not true, but it's an easy way for doctors to explain the
problem, however oversimplified and inaccurate. With the exception of muscle
paralysis, the eye muscles in a crossed or wandering eye are not weak.
The problem is not muscular, but neuromuscular; the problem lies in the signal
from the brain to the muscles which control eye alignment. Strabismus is the
result of faulty coordination between the brain and eye muscles--in other
words, strabismus is a brain-based problem.
simple procedure can demonstrate that there is nothing inherently wrong with
the eye muscles in a crossed eye. Place your finger in front of the child and
have him look at it. Now cover the straight eye with your other hand and watch
the crossed eye. It immediately straightens. The muscles in the crossed eye
automatically aim the eye without difficulty. The real problem is not weak
muscles, but the inability of the brain to control the muscles in both eyes
at the same time--in other words, faulty signals from of the brain to the
two eyes together.
recommendation for strabismic surgery is often oversimplified, such as
"the weak eye muscles must be operated upon to realign the eye and
correct the problem." There are two large fallacies in this
recommendation: 1) Since weak muscles aren't the true cause of strabismus,
then surgical intervention is addressing only a symptom, not the underlying
cause. 2) In the vast majority of cases, surgery does not "correct"
the child's inability to use both two eyes together; it only cosmetically
aligns the eyes so they look straight.
any parent of a child with strabismus, it is imperative that they educate
themselves and realistically understand the limitations of surgery. Eye
muscle surgery to correct strabismus concerns itself only with making the eye
appear straight--a cosmetic "fix" but not a visual cure.
In fact, the surgical standard to determine a successful outcome of the
surgery is based on appearance. Ophthalmologists consider a surgery
"successful" if afterwards the eyes are aligned within ten degrees
of each other with no consideration given to improvement in vision.
That's not their goal. Why? Because surgery does not usually
improve visual function. Surgery deals only with extraocular muscles,
not the brain and it's visual processing pathways. Surgery simply cannot
correct the nerve pathways from the brain to the eye which caused the crossed
eye to begin with. Surgery does nothing to train the brain how to use
both eyes together.
Instead, the process of invasive surgery and resulting scar tissue only
compounds the real problem, making later nonsurgical intervention much more
children who have undergone surgery for a crossed eye still suppress one eye
full time. Suppression is the brain's learned response to avoid double vision.
Suppression must be unlearned and the brain trained to use both eyes together
if normal functional vision is to be restored. Less than 20% of children
who undergo eye surgery for a crossed eye eventually achieve binocular fusion
(two-eyed vision) with normal depth perception and visual function. The
few who do are nearly always very young children whose visual systems were
still developing and fluid enough to fall into binocularity on their own. This
is not true for the vast majority, however. Over 80% of surgery patients still
live in a monocular, one-eyed world without depth and distance judgments.
with exotropia, or a wandering eye that floats out from the nose, fair a
little better with surgery. Children whose eye turns out only
occasionally have the best clinical results from surgery. About 1/3 can
achieve normal vision afterward--but 2/3 do not!
because the eye looks straight after surgery, most parents do not realize
their child's vision hasn't improved at all. And because the real cause
of strabismus was not addressed, the cosmetic results of surgery are often not
permanent. Over time, the eye begins to turn again and repeated operations are
required to realign the eye.
is a better alternative.
surgery, vision therapy addresses the real cause of strabismus. Therapy
improves the coordination between the brain and eyes, eliminates suppression,
and teaches the brain how to use both eyes together so that the eyes remain
straight. By treating the underlying cause of strabismus, vision therapy
restores normal vision. Therapy corrects the child's vision system by teaching
the eyes how to aim together and training the brain to receive and fuse the
visual images from both eyes at the same time. Ninety percent (90%) of therapy
patients complete treatment with eyes which are straight and a visual system
which operates normally. Most importantly, because binocular fusion (two-eyed
vision) is the "glue" which holds the eyes straight, the results are
Why, then, when therapy is
so effective in curing strabismus is surgery so often recommended? Part of the
answer lies in the "David and Goliath" syndrome. There are more than
12,000 eye surgeons. Their job is to perform surgery. By no means are eye
surgeons, or ophthalmologists, to be discredited. Theirs is an important job,
and the surgeries they perform--from cataract removal to refractive laser
surgery--improve the quality of their patients' lives. However, American
ophthalmologists have no training in vision therapy and have only a very
limited knowledge in functional vision remediation. When it comes to
strabismus, the only treatment that ophthalmologists have with their surgical
background is operating on the eyes to make them appear straight. (This is not
true in Europe. European ophthalmologists have much more extensive training in
functional vision training, and therapy is nearly always recommended before
number of American doctors specializing in vision therapy, on the other hand,
is much smaller. There are less than 1,600 developmental
optometrists specializing in vision therapy. These doctors are Fellows or
Associates in the College of Optometrists in Vision Development, the national
certifying organization for doctors who specialize in vision therapy.
All Fellows have passed a rigorous national board to receive their
certification in the remediation of binocular vision problems. Because of
their training and background, C.O.V.D. Fellows are functional vision
specialists with the knowledge and expertise to fully correct strabismus. But
because their numbers are so much smaller nationwide, so is their patient
of the reasons that there are so few eye doctors specializing is vision
therapy is economics. Therapy is not as time efficient and economically
rewarding for doctors as surgery. In addition, maintaining the staff,
treatment space, and time required to commit to extended therapy can consume a
large part of an optometrist's practice. Those doctors who commit themselves
to providing vision therapy do so out of a sincere desire to offer their
patients the best care possible.
the end, parents must make an informed decision about which type of treatment
option they will pursue. If your child has strabismus, the best advice is to
educate yourself on the pros and cons of each option. Make an appointment with
both a surgical ophthalmologist and a developmental
optometrist who provides vision therapy. Be proactive. Ask questions: Does
what you've been told make sense? Does it seem reasonable? What are the risks
of the treatment being proposed? Did you get all your questions answered by
the doctor? In the end, parents must formulate treatment goals and carefully
consider their options when entrusting their child's vision to any eye care
you need help locating a developmental optometrist who
provides vision therapy, you can call the national certifying board of the
College of Optometrists in Vision Development at 1-888-268-3770 toll free or
visit their web site at http://www.covd.org.
Also, your family optometrist can be a good resource. Ask if he or she
provides vision therapy or if they can make a referral to a colleague who