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.

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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. 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.

Amblyopia, or lazy eye, is closely related to strabismus. Children learn to suppress double vision so effectively that the deviating eye gradually loses vision. It may be necessary to patch the good eye and wear glasses before treating the strabismus. Amblyopia does not occur when alternate eyes deviate, and adults do not develop amblyopia.

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 though the results are rarely perfect. Results are usually better in young children. Surgery can be done with local anesthesia in some adults, but requires general anesthesia in children, usually as an outpatient. Prisms and Botox injections of the eye muscles are alternatives to surgery in some cases. Eye exercises are rarely effective.

Adult Strabismus

What is adult strabismus? Strabismus is the medical term relating to a misalignment of the eyes and may develop at any time during an individual's lifetime. When strabismus occurs in an adult for the first time, it produces double vision or diplopia.

Causes of strabismus in adulthood

The most common causes of strabismus in adults are:

  1. Re-occurrence of ocular misalignment in an adult who had strabismus in childhood. Despite adequate treatment for strabismus in childhood, strabismus may recur later in life. This is usually caused by inability to use both eyes together (binocular vision).
  2. Poor vision in one eye. People who have one eye that doesn't see well, even when corrected with appropriate glasses, frequently develop strabismus of the poorly seeing eye; in most cases, the eye will deviate outward.
  3. Problems affecting the brain, such as stroke, tumor or head trauma, may injure nerves that control the normal movement of one or more eye muscles, causing strabismus. Double vision in older adults is most often caused by high blood pressure or diabetes.

Treatment of strabismus in adults

Treatment of strabismus in adults depends on the cause and size of the strabismus. Small deviations that cause double vision may be treated successfully with prism glasses. These glasses do not cure the problem, but instead compensate for it by correcting the direction and focusing the light rays that enter the eye, thereby eliminating the double vision. Only small angle deviations are treated with prisms, as large amounts of prism distort and blur vision, and may be very thick and heavy.

Most strabismus caused by microvascular disease resolve within several months. Therefore, the treatment for this type of strabismus is"tincture of time". Patching of one eye, the use of prism glasses or injection of Botox (botulinum toxin) to an eye muscle may alleviate the bothersome double vision until nature and time have corrected the problem.

Patients with longstanding strabismus, poor vision in one eye that has led to the development of strabismus, or ocular misalignment that results from head trauma or tumor may require surgical correction on the eye muscles of one or both eyes to achieve functional and restorative benefits.

Summary

Adult strabismus is very common and may develop for many reasons. Most adults are helped through a variety of treatment modalities, depending on the etiology and magnitude of the deviation. A sudden onset of double vision, without a history of head trauma, is an emergency, indicating a need for swift medical attention.