strabismus (redirected from concomitant strabismus)

strabismus (strəbĭz`məs), inability of the eyes to focus together because of an imbalance in the muscles that control eye movement; also called squint. It is a consequence of weakness or uneven development of one or more of the six small muscles that surround the eye. One or both eyes may be affected. Horizontal strabismus is caused when the eyes do not move together laterally; this condition is known as cross-eye if the eye turns inward or walleye if the eye turns outward. Vertical strabismus results when the eye rolls upward or downward in its socket. There is also torsional strabismus in which the eyes do not rotate together about their optical axes. Strabismus is usually present at birth and becomes apparent early in infancy, but it may also result from illness or injury. Because the condition results in perception of a double image, there is a tendency to use only one eye. It is important that treatment be started as soon as possible to prevent loss of sight in the unused eye. Corrective therapy includes exercise that strengthens eye muscles and prescription of corrective lenses. Sometimes a patch is placed alternately on each eye so that neither is allowed to become completely unused. If necessary, the eye muscles may be shortened or lengthened surgically.

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strabismus

 or squint or heterotropia

Failure of the eyes to align properly to focus on an object. The affected eye may deviate in any direction, including inward (cross-eye) or outward (walleye). Problems with photoreception or the nerves that relay images to the brain cause a constant degree of deviation (comitant); defects in the nerves that control the muscles that move the eyes cause deviation that varies with the direction of gaze (noncomitant). Both types impede development of a child's ability to focus the eyes and merge images from the two retinas into one (fusional reflex). The brain suppresses the image from the deviant eye, which may become functionally blind. Treatment may involve exercises to strengthen the weak eye or surgery or both.