Strabismus (/strəˈbɪzməs/, from Greek strabismós) is a condition that interferes with binocular vision because it prevents a person from directing both eyes simultaneously towards the same fixation point; the eyes do not properly align with each other. Heterotropia is a medical synonym for the condition. Colloquial terms for strabismus include cross-eye, wall-eye, a squint and a cast of the eye.Strabismus typically involves a lack of coordination between the extraocular muscles, which prevents directing the gaze of both eyes at once to the same point in space; it thus hampers proper binocular vision, and may affect depth perception adversely. Strabismus is primarily managed by ophthalmologists, optometrists, and orthoptists. Strabismus is present in about 4% of children. Treatment should be started as early as possible to ensure the development of the best possible visual acuity and stereopsis.