Strabismus
Strabismus refers to misaligned eyes. If the eyes turn inward (crossed), it is called esotropia.
If the eyes turn outward (wall-eyed), it is called
exotropia. Or, one
eye can be higher than the other which is called hypertropia (for the higher
eye) or hypotropia (for the lower eye). Strabismus can be subtle or obvious,
intermittent (occurring occasionally), or constant. It can affect one eye only
or shift between the eyes.
Strabismus
usually begins in infancy or childhood. Some toddlers have accommodative
esotropia. Their eyes cross because they need glasses for farsightedness. But
most cases of strabismus do not have a well-understood cause. It seems to
develop because the eye muscles are uncoordinated and do not move the eyes
together. Acquired strabismus can occasionally occur because of a problem in the
brain, an injury to the eye socket, or thyroid eye disease.
When
young children develop strabismus, they typically have mild symptoms and do not
complain of double vision. They may hold their heads to one side if they can use
their eyes together in that position. Or, they may close or cover one eye when
it deviates, especially at first. Adults, on the other hand, have more symptoms
when they develop strabismus. They have double vision (see a second image) and
may lose depth perception. At all ages, strabismus is disturbing. Studies show
school children with significant strabismus have self-image problems.
Children
have the ability to suppress the deviating eye which prevents them from having
the symptoms of diplopia. Unfortunately, because of this suppression of the
deviating eye, it can develop a gradual loss of vision. Amblyopia can cause
permanent loss of vision if not treated at an early age by the appropriate
therapeutic techniques. Additionally, the misalignment of the eyes prevents
their simultaneous usage (fusion) and depth perception. Depth perception is
based on both eyes perceiving simultaneous images of an object. These images are
slightly different, because of the different angle from which each eye views an
object. The brain is able to interpret this image disparity and develop a
perception of the objects location in space (steropsis). For fusion and
steropsis to develop and be maintained correction of any misalignment of the
eyes must be performed.
Strabismus is often treated by surgically adjusting the tension on the eye muscles. The goal of surgery is to get the eyes close enough to perfectly straight that it is hard to see any residual deviation. Surgery usually improves the conditions, however more than one surgery may be necessary. Surgery usually requires general anesthesia and can be performed as an outpatient. Prisms and glasses are alternatives to surgery in some cases.