Q:
What is it?
A: Strabismus is a visual defect in which the eyes are misaligned
and point in different directions. We've become accustomed to
referring to this condition as crossed eyes, but actually strabismus
refers to any situation where the eyes are not pointed in the
same direction. This occurs when the muscles that control eye
position and movement do not work together properly. When that
happens, one eye might be pointing in or out, or up or down,
while the other eye is looking straight ahead. If the eyes are
looking in two different directions, they will each see a different
image. Then, not only is it difficult or impossible to judge
depth, but the brain learns to favor one image over another.
Crossed eyes, if not corrected early, can lead to a condition
known as lazy eye, or what eye specialists call amblyopia. This
occurs when the same eye always turns away and becomes weaker
or lazy. If not treated, that eye will eventually become useless.
The two most common types of strabismus are esotropia and exotropia.
Esotropia describes an inward turning eye. Exotropia describes
an outward turning eye. Children as well as adults can have
strabismus. Strabismus affects about 4% of the children's population.
Strabismus can be hereditary. However, many people have strabismus
with no trace of the problem in any other family member.
Q: What are the signs or symptoms?
A: The primary symptom of strabismus is an eye that is not
straight. Sometimes a child will squint one eye in bright sunlight
or tilt their head in a specific direction in order to use their
eyes together, signs of faulty depth perception may also be
noticed. Adults who acquire strabismus will usually have double
vision. It's difficult for a parent to determine whether or
not an infant's eyes are working together properly. At birth,
and for the first few months of life, a baby's eyes sometimes
seem to be moving independently of one another. Yet the eyes
are gaining in strength and coordination, and usually by six
months of age they are functioning as they should.
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Q:
What causes it?
A: The
exact cause of eye misalignment that leads to strabismus is
not fully understood. To line up and focus both eyes on a
single object, all eye muscles of each eye must be balanced
and working together with the corresponding muscles of the
opposite eye. The brain controls the eye muscles, which explains
why children with disorders that affect the brain, such as
cerebral palsy, Down's syndrome, hydrocephalus and brain tumors,
often have strabismus. A cataract or eye injury that affects
vision can also cause strabismus.
Q:
How is it detected?
A: Children
should have a thorough medical examination during infancy
and preschool years to detect potential eye problems. This
is particularly important if a relative has strabismus.
Q:
How is it treated?
A: Treatment
goals for strabismus are to preserve vision, and to straighten
the eyes, and to restore binocular vision. The simplest treatment
is corrective lenses. Eye drops may be prescribed. In some
cases, eye exercises are helpful. Eye patches, used in combination
with glasses or surgery are beneficial to some patients. Surgery
not only permits the eyes to develop normally, but it also
improves one's appearance. Early surgery is recommended to
correct strabismus because younger infants can develop normal
sight and binocular vision once the eyes are straightened.
As a child gets older, the chance of developing normal sight
and binocular vision decreases, although side vision may improve.
Correction of strabismus after age 6 will improve appearance,
but cannot provide a second chance to learn binocularity.
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