Strabismus (redirected from crossed eye)

Strabismus 

Definition

Strabismus is a condition in which the eyes do not point in the same direction. It can also be referred to as a tropia or squint.

Description

Strabismus occurs in 2-5% of all children. About half are born with the condition, which causes one or both eyes to turn:

Strabismus is equally common in boys and girls. It sometimes runs in families.

Types of strabismus

Esotropia is the most common type of strabismus in infants. Accommodative esotropia develops in children under age two who cross their eyes when focusing on objects nearby. This usually occurs in children who are moderately to highly farsighted (hyperopic).

Another common form of strabismus, exotropia, may only be noticeable when a child looks at far-away objects, daydreams, or is tired or sick.

Sometimes the eye turn is always in the same eye; however sometimes the turn alternates from one eye to the other'.

Most children with strabismus have comitant strabismus. No matter where they look, the degree of deviation does not change. In incomitant strabismus, the amount of misalignment depends upon which direction the eyes are pointed.

False strabismus (pseudostrabismus)

A child may appear to have a turned eye, however this appearance may actually be due to:

This condition, false strabismus, usually disappears as the child's face grows. An eye doctor needs to determine whether the eyeturn is true or pseudostrabismus.

With normal vision, both eyes send the brain the same message. This binocular fixation (both eyes looking directly at the same object) is necessary to see three-dimensionally and to aid in depth perception. When an eye is misaligned, the brain receives two different images. Young children learn to ignore distorted messages from a misaligned eye, but adults with strabismus often develop double vision (diplopia).

A baby's eyes should be straight and parallel by three or four months of age. A child who develops strabismus after the age of eight or nine years is said to have adult-onset strabismus.

Causes and symptoms

Strabismus can be caused by a defect in muscles or the part of the brain that controls eye movement. It is especially common in children who have:

Diseases that cause partial or total blindness can cause strabismus. So can extreme farsightedness, cataracts, eye injury, or having much better vision in one eye than the other.

In adults, strabismus is usually caused by:

The most obvious symptom of strabismus is an eye that isn't always straight. The deviation can vary from day to day or during the day. People who have strabismus often squint in bright sunlight or tilt their heads to focus their eyes.

Diagnosis

Every baby's eyes should be examined by the age of six months. A baby whose eyes have not straightened by the age of four months should be examined to rule out serious disease.

A pediatrician, family doctor, ophthalmologist, or optometrist licensed to use diagnostic drugs uses drops that dilate the pupils and temporarily paralyze eye-focusing muscles to evaluate visual status and ocular health. Early diagnosis is important. Some eye turns may be a result of a tumor. Untreated strabismus can damage vision in the unused eye and possibly result in lazy eye (amblyopia).

Treatment

Preserving or restoring vision and improving appearance may involve one or more of the following:

Prognosis

Early consistent treatment usually improves vision and appearance. The most satisfactory results are achieved if the condition is corrected before the age of seven years old.

Resources

Organizations

American Academy of Ophthalmology. 655 Beach Street, P.O. Box 7424, San Francisco, CA 94120-7424. http://www.eyenet.org.

American Academy of Pediatric Ophthalmology and Strabismus (AAPOS). 〈http://med-aapos.bu.edu〉.

American Optometric Association. 243 North Lindbergh Blvd., St. Louis, MO 63141. (314) 991-4100. http://www.aoanet.org.

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strabismus /stra·bis·mus/ (strah-biz´mus) squint; deviation of the eye which the patient cannot overcome; the visual axes assume a position relative to each other different from that required by the physiological conditions.strabis´mic

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concomitant strabismus  that due to faulty insertion of the eye muscles, resulting in the same amount of deviation regardless of the direction of the gaze.

convergent strabismus  esotropia.

divergent strabismus  exotropia.

nonconcomitant strabismus  that in which the amount of deviation of the squinting eye varies according to the direction of gaze.

vertical strabismus  that in which the visual axis of the squinting eye deviates in the vertical plane (hypertropia or hypotropia).

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stra·bis·mus (str-bzms)

n.

A visual defect in which one eye cannot focus with the other on an objective because of imbalance of the eye muscles. Also called heterotropia, squint, tropia.

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stra·bismal (-ml), stra·bismic (-mk) adj.

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strabismus (str·bizˑ·ms),

n a condition wherein the two visual axes of the eyes are not aimed at a single object. In paralytic strabismus the muscles in the eyes are unable to move because of infection, tumor, or injury. In nonparalytic strabismus, there is a defect in the location of the eyes in relationship to their focal point. Also called
squint.

Strabismus.

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strabismus (strbiz´ms),

n an abnormal ocular condition in which the eyes are crossed.

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strabismus

deviation of the eye that the patient cannot overcome; the visual axes assume a position relative to each other different from that required by the physiological conditions. Called also squint.

Basic types of strabismus. By permission from Guyton R, Hall JE, Textbook of Medical Physiology, Saunders, 2000

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comitant strabismus

extraocular muscles are not paralyzed and the degree of deviation is the same in all directions.

congenital strabismus

medial strabismus is seen in Siamese cats. See convergent strabismus (below).

convergent strabismus

that in which the visual axes converge; esotropia, or cross-eye. A frequent finding in Siamese cats, related to an anomaly of neuronal pathways between the retina and lateral geniculate nucleus in which more neurons project contralaterally rather than ipsilaterally as in other cats.

divergent strabismus

that in which the visual axes diverge; called also exotropia and walleye.

inherited strabismus

see inherited exophthalmos.

noncomitant strabismus

deviation due to paralysis of one or more muscles.

traumatic strabismus

a complication of traumatic prolapse of the eye, due to rupture of extraocular muscles.