A condition in which the visual axes of the eyes are not parallel and the eyes appear to be looking in different directions. In divergent strabismus, or exotropia, the visual axes diverge. If the visual axes converge, it is called convergent strabismus or esotropia. The danger with strabismus is that the brain cones may come to rely more on one eye than the other and that part of the brain circuitry connected to the less-favored eye fails to develop properly, leading to amblyopia (blindness) in that eye. The classic treatment for mild-to-moderate strabismus has long been an eyepatch, covering the stronger eye with a patch, forcing the weaker eye to do enough work to catch up. However, eyedrops can work as well as an eyepatch in correcting moderate lazy eye and preventing the development of amblyopia (blindness). Atropine eyedrops are instilled daily in the stronger (dominant) eye. The atropine works by blurring rather than blocking vision in the stronger eye. Severe strabismus may require surgery. The surgery is designed to increase or decrease the tension of the small muscles outside the eye. (These muscles are called the extraocular eye muscles. The six extraocular eye muscles move the eye in all directions.) When strabismus surgery is needed, the sooner it is done, the better the chance of the child achieving normal binocular vision. Adults sometimes also need strabismus surgery. This can be done in a standard manner, as in children. Or adjustable suture surgery may be done because scarring from old eye surgery, inflammation from eye muscle disease, or neurological eye weakness makes it difficult to gauge how much tension to take up or let out to straighten the eyes. With adjustable suture surgery, it is possible to adjust the tension of the muscles after the surgery. Strabismus is also called cast, heterotropia, manifest deviation and squint. The term "strabismus" comes from the Greek "strabismos" = a squinting.
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A manifest lack of parallelism of the visual axes of the eyes. SYN: crossed eyes, heterotropia, heterotropy, squint (1). [Mod. L., fr. G. strabismos, a squinting]
- A-s. 1. s. in which esotropia is more marked in looking upward than downward; 2. s. in which exotropia is more marked on looking downward than upward. SYN: A-pattern s..
- accommodative s. s. in which the severity of deviation varies with accommodation.
- alternate day s. SYN: cyclic esotropia.
- alternating s. a form of s. in which either eye fixes.
- A-pattern s. SYN: A-s..
- comitant s. a condition in which the degree of s. is the same in all directions of gaze. SYN: concomitant s..
- concomitant s. SYN: comitant s..
- cyclic s. a s. that appears and disappears in rhythym, most frequently at 48-hour intervals.
- divergent s. SYN: exotropia.
- incomitant s. SYN: paralytic s..
- kinetic s. s. due to spasm of an extraocular muscle.
- manifest s. evident deviation of one eye or the other; may be alternating or monocular.
- mechanical s. s. due to restriction of action of the ocular muscle within the orbit.
- paralytic s. s. due to weakness of an ocular muscle or muscles. SYN: incomitant s..
- vertical s. a form of s. in which the visual axis of one eye deviates upward (s. sursum vergens) or downward (s. deorsum vergens).
- X-s. s. in which exotropia is more marked when looking upward or downward than when looking straight ahead.

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stra·bis·mus strə-'biz-məs n inability of one eye to attain binocular vision with the other because of imbalance of the muscles of the eyeball called also heterotropia, squint compare cross-eye

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squint: any abnormal alignment of the two eyes. The strabismus is most commonly horizontal - convergent strabismus (or esotropia) or divergent strabismus (exotropia) - but it may be vertical (hypertropia, in which the eye looks upwards, or hypotropia, in which it looks downwards). In rare cases both eyes look towards the same point but one is twisted clockwise or anticlockwise in relation to the other (cyclotropia). Double vision is possible, but the image from the deviating eye usually becomes ignored. In cyclotropia the image is not separated from the normal one but rotated across it. Most strabismus is concomitant, i.e. the abnormal alignment of the two eyes remains fairly constant, in whatever direction the person is looking. This is usual with childhood squints. Strabismus acquired by injury or disease is usually incomitant, i.e. the degree of misalignment varies in different directions of gaze. See also cover test, deviation, divergence, heterophoria.

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stra·bis·mus (strə-bizґməs) [Gr. strabismos a squinting] an eye condition in which the visual axes cannot be directed at the same point of fixation under normal conditions of seeing. The various forms of strabismus are spoken of as tropias, with their direction indicated by the appropriate prefix, such as cyclotropia, esotropia, exotropia, hypertropia, and hypotropia. Called also cast, heterotropia, manifest deviation, and squint. strabismal, strabismic adj

Medical dictionary. 2011.

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