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Causes of horizontal strabismus in children

David K Coats, MD
Evelyn A Paysse, MD
Section Editor
Richard A Saunders, MD
Deputy Editor
Carrie Armsby, MD, MPH


Strabismus is the term used to describe an anomaly of ocular alignment (see "Evaluation and management of strabismus in children", section on 'Terminology'). The eye misalignment can involve either eye and can occur in any direction; it can be congenital or acquired, latent or manifest, constant or intermittent, and fixed or variable, depending upon the position of gaze and other factors.

Strabismus can be classified according to the direction of deviation: in (esodeviations), out (exodeviations), and up or down (vertical deviations). The causes of horizontal strabismus are reviewed here. The evaluation of strabismus and the causes of vertical strabismus are discussed separately. (See "Evaluation and management of strabismus in children" and "Causes of vertical strabismus in children".)


Three pairs of extraocular muscles move each eye in three directions: vertically (superior and inferior), horizontally (medially [adduction] and laterally [abduction]), and torsionally (intorsion when the eye rotates nasally and extorsion when the eye rotates temporally along the visual axis). The superior oblique muscle is innervated by cranial nerve IV, the lateral rectus muscle by cranial nerve VI, and all others by cranial nerve III (table 1).

The understanding of strabismus requires knowledge of the two major principles that govern ocular motility [1]:

Agonist muscles in both eyes receive equal innervation to ensure coordinated binocular eye movements. Thus, when the right lateral rectus muscle is activated to abduct the right eye, the left medial rectus muscle is activated equally to adduct the left eye.

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Literature review current through: Nov 2017. | This topic last updated: Aug 16, 2017.
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