WordNet

move or draw apart; "The two paths diverge here"
extend in a different direction; "The lines start to diverge here"; "Their interests diverged"
have no limits as a mathematical series
diverging from another or from a standard; "a divergent opinion"
tending to move apart in different directions (同)diverging
abnormal alignment of one or both eyes (同)squint

PrepTutorEJDIC

(一点から)分岐する,分かれる《+『from』+『名』》 / (定まったコースから)それる,外れる《+『from』+『名』》
分岐する;それている
斜視,やぶにらみ

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/10 08:59:25」(JST)

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For the similar condition, where the eyes deviate inward (rather than outward), see esotropia.

Exotropia (from Greek εξοτρὀπια, εξο "exo" meaning "to exit" or "move out of" and τρὀπειν "tropein" meaning "to turn") is a form of strabismus where the eyes are deviated outward. It is the opposite of esotropia. People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly common condition. "Sensory exotropia" occurs in the presence of poor vision. Infantile exotropia (sometimes called "congenital exotropia") is seen during the first year of life, and is less common than "essential exotropia" which usually becomes apparent several years later.

The brain's ability to see three-dimensional objects depends on proper alignment of the eyes. When both eyes are properly aligned and aimed at the same target, the visual portion of the brain fuses the forms into a single image. When one eye turns inward, outward, upward, or downward, two different pictures are sent to the brain. This causes loss of depth perception and binocular vision.

Causes

The causes of exotropia are not fully understood. There are six muscles that control eye movement, four that move the eye up and down and two that move it side to side. All these muscles must be coordinated and working properly in order for the brain to see a single image. When one or more of these muscles doesn't work properly, some form of strabismus may occur. Strabismus is more common in children with disorders that affect the brain such as cerebral palsy, Down syndrome, hydrocephalus, and brain tumors. One study has found that children with exotropia are three times more likely to develop a psychiatric disorder in comparison with the general population.^[1]^[2]^[3]

Signs and symptoms

The earliest sign of exotropia is usually a noticeable outward deviation of the eye. This sign may at first be intermittent, occurring when a child is daydreaming, not feeling well, or tired. Boss-eye may also be more noticeable when the child looks at something in the distance. Squinting or frequent rubbing of the eyes is also common with exotropia. The child probably will not mention seeing double, i.e., double vision. However, he or she may close one eye to compensate for the problem.

Generally, exotropia progresses in frequency and duration. As the disorder progresses, the eyes will start to turn out when looking at close objects as well as those in the distance. If left untreated, the eye may turn out continually, causing a loss of binocular vision.

In young children with any form of strabismus, the brain may learn to ignore the misaligned eye's image and see only the image from the best-seeing eye. This is called amblyopia, or lazy eye, and results in a loss of binocular vision, impairing depth perception. In adults who develop strabismus, double vision sometimes occurs because the brain has already been trained to receive images from both eyes and cannot ignore the image from the turned eye.

Additionally in adults who have had exotropia since childhood, the brain may adapt to using a "blind-spot" whereby it receives images from both eyes, but no full image from the deviating eye, thus avoiding double vision and in fact increasing peripheral vision on the side of the deviating eye.

Treatment

A comprehensive eye examination including an ocular motility (eye movement) evaluation and an evaluation of the internal ocular structures will allow an eye doctor to accurately diagnose the exotropia. Although glasses and/or patching therapy, exercises, or prisms may reduce or help control the outward-turning eye in some children, surgery is often required.

There is a common form of exotropia known as "convergence insufficiency" that responds well to orthoptic vision therapy including exercises. This disorder is characterized by an inability of the eyes to work together when used for near viewing, such as reading. Instead of the eyes focusing together on the near object, one deviates outward.

Because of the risks of surgery, and because about 35% of people require at least one more surgery, many people try vision therapy first. This consists of visual exercises. It is generally not covered by health insurance companies.

Surgery is sometimes recommended if the exotropia is present for more than half of each day or if the frequency is increasing over time. Surgery is also indicated if a child has significant exotropia when reading or viewing near objects or if there is evidence that the eyes are losing their ability to work as a single unit (binocular vision). If none of these criteria are met, surgery may be postponed pending simple observation with or without some form of eyeglass and/or patching therapy. In very mild cases, there is a chance that the exotropia will diminish with time.

The surgical procedure for the correction of exotropia involves making a small incision in the tissue covering the eye in order to reach the eye muscles. The appropriate muscles are then repositioned in order to allow the eye to move properly. The procedure is usually done under general anesthesia. Recovery time is rapid, and most people are able to resume normal activities within a few days. Following surgery, corrective eyeglasses may be needed and, in many cases, further surgery is required later to keep the eyes straight.

When a child requires surgery, the procedure is usually performed before the child attains school age. This is easier for the child and gives the eyes a better chance to work together. As with all surgery, there are some risks. However, strabismus surgery is usually a safe and effective treatment.

References

Notes

^ Mohney BG, McKenzie JA, Capo JA, Nusz KJ, Mrazek D, Diehl NN (November 2008). "Mental illness in young adults who had strabismus as children". Pediatrics 122 (5): 1033–8. doi:10.1542/peds.2007-3484. PMC 2762944. PMID 18977984. http://pediatrics.aappublications.org/cgi/pmidlookup?view=long&pmid=18977984.
^ Mayo Clinic. "Eye Divergence In Children Triples Risk Of Mental Illness." ScienceDaily 28 November 2008. 30 November 2008
^ McKenzie J, et al "Prevalence and sex differences of psychiatric disorders in young adults who had intermittent exotropia as children" Arch Ophthalmol 2009; 127:743-47.[1]

UpToDate Contents

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1. 小児における斜視の評価およびマネージメント evaluation and management of strabismus in children
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3. 小児における垂直斜視の原因 causes of vertical strabismus in children
4. 小児における第4脳神経（滑車神経）麻痺 fourth cranial nerve trochlear nerve palsy in children
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English Journal

The stability of the monofixation syndrome.

Ing MR1, Roberts KM2, Lin A3, Chen JJ3.Author information 1University of Hawaii, John A. Burns School of Medicine, Honolulu, Hawaii. Electronic address: malcolmingmd@hotmail.com.2University of Hawaii, Honolulu, Hawaii.3University of Hawaii, John A. Burns School of Medicine, Honolulu, Hawaii.AbstractPURPOSE: To determine etiology, characteristics, and stability of the monofixation syndrome (MFS) in a chart review of 63 consecutive patients in a private practice of pediatric ophthalmology.
American journal of ophthalmology.Am J Ophthalmol.2014 Jan;157(1):248-253.e1. doi: 10.1016/j.ajo.2013.08.024. Epub 2013 Nov 5.
PURPOSE: To determine etiology, characteristics, and stability of the monofixation syndrome (MFS) in a chart review of 63 consecutive patients in a private practice of pediatric ophthalmology.DESIGN: Retrospective, consecutive chart review.METHODS: The charts of 63 consecutive patients with MFS, en
PMID 24200233

A co-occurrence of familial isolated cherry red spot and multiple lens opacities.

Esmer O1, Karadag R2, Soylu E1, Dogan M3.Author information 1Department of Ophthalmology, School of Medicine, Yuzuncu Yil University, Van, Turkey.2Department of Ophthalmology, School of Medicine, Istanbul Medeniyet University, Istanbul, Turkey.3Department of Pediatrics, Division of Pediatric Endocrinology, School of Medicine, Yuzuncu Yil University, Van, Turkey.AbstractPurposeTo present a co-occurrence of familial isolated cherry red spot (CRS) and multiple lens opacities in all siblings from the same family without any other systemic or ocular diseases.MethodsFour siblings from the same family had bilateral punctate lens opacities and bilateral CRS at the macula.ResultsThe oldest one had left eye exotropia and amblyopia, otherwise the other siblings had no additional ocular findings. Systemic investigation, physical examination, and laboratory tests were within normal limits.ConclusionBilateral isolated CRS along with punctate lens opacities were seen in all siblings from the same family without any systemic and ocular diseases.Eye advance online publication, 20 December 2013; doi:10.1038/eye.2013.271.
Eye (London, England).Eye (Lond).2013 Dec 20. doi: 10.1038/eye.2013.271. [Epub ahead of print]
PurposeTo present a co-occurrence of familial isolated cherry red spot (CRS) and multiple lens opacities in all siblings from the same family without any other systemic or ocular diseases.MethodsFour siblings from the same family had bilateral punctate lens opacities and bilateral CRS at the macula.
PMID 24357834