Squint

Squint has two principal senses. As a verb, it means to look with the eyes partly closed, usually to reduce glare or to see more clearly. As a noun, especially in British English, squint is a medical term for strabismus, a condition in which the eyes are not properly aligned.

Strabismus is a misalignment of the eyes that can affect one or both eyes. Clinically, it may be latent, known as heterophoria, or manifest, known as heterotropia. It is further classified as concomitant (the misalignment is roughly constant in all directions) or incomitant (the degree of misalignment varies with gaze), and as constant or intermittent.

Causes include refractive errors, congenital muscle imbalance, and nerve or brain conditions affecting eye movement. Acquired strabismus may result from trauma, stroke, or ocular diseases, while congenital strabismus is present from birth or early infancy. Family history and prematurity are risk factors.

Symptoms range from visible eye misalignment to double vision in adults; in children, suppression of the image from one eye and development of amblyopia (lazy eye) can occur, potentially reducing depth perception. Some individuals adopt a head posture to compensate.

Diagnosis relies on eye alignment testing, including cover tests, the Hirschberg test, and refraction. Treatment is tailored to type and age and may involve glasses or contact lenses, occlusion or penalization therapy for amblyopia, vision therapy, or botulinum toxin injections. Surgical adjustment of the eye muscles can correct the alignment when non-surgical methods are insufficient, often improving binocular vision.

Prognosis is best with early detection in childhood; untreated strabismus can lead to persistent vision problems and reduced stereopsis. See also strabismus, amblyopia.