strabismus

Strabismus, commonly referred to as squint or heterotropia, is a condition in which the eyes are not aligned and point in different directions. The misalignment can affect one eye at a time or alternate between eyes and may be constant or intermittent. In children, strabismus can lead to impaired depth perception and amblyopia if not treated.

Causes and prevalence vary. Strabismus may result from neurologic or muscular abnormalities that affect the extraocular muscles, refractive errors such as uncorrected hyperopia, or congenital factors. It can also occur after illness or injury affecting the nerves or muscles that move the eyes. Strabismus is more common in children, with estimates around a few percent of childhood populations. Adults may develop it from past misalignment or new onset due to disease.

Types are categorized by direction of misalignment: esotropia (inward turning), exotropia (outward turning), hypertropia (upward deviation), and hypotropia (downward deviation). The condition can be constant or intermittent and may be comitant (similar deviation in all directions) or incomitant (varying with gaze).

Signs and diagnosis include observable eye misalignment, abnormal cover tests, and reduced or absent binocular vision. A comprehensive eye examination assesses visual acuity, refractive error, ocular motility, and may include neuroimaging or ophthalmologic evaluation to exclude underlying pathology.

Treatment aims to improve alignment and binocular vision. Approaches include glasses to correct refractive error, patching or penalization to treat amblyopia, vision therapy, botulinum toxin injections into extraocular muscles, and strabismus surgery to adjust muscle strength. Early intervention improves outcomes, especially for children. Complications can include persistent diplopia, poor depth perception, and longstanding amblyopia if not addressed.