strabismus /strəbiz″məs/ [Gk, strabismos, squint] , an abnormal ocular condition in which the visual axes of the eyes are not directed at the same point. There are two kinds of strabismus, paralytic and nonparalytic. Paralytic strabismus results from the inability of the ocular muscles to move the eye because of neurologic deficit or muscular dysfunction. The muscle that is dysfunctional may be identified by watching as the patient attempts to move the eyes to each of the cardinal positions of gaze. If the affected eye cannot be directed to a position, the examiner infers that the associated ocular muscle is the dysfunctional one. Because this kind of strabismus may be caused by tumor, infection, or injury to the brain or the eye, an ophthalmologic examination is recommended. Nonparalytic strabismus is a defect in the position of the two eyes in relation to each other. The condition may be inherited. The person cannot use the two eyes together but has to fixate with one or the other. The eye that looks straight at a given time is the fixing eye. Some people have alternating strabismus, using one eye and then the other; some have monocular strabismus, which affects only one eye. Visual acuity diminishes with diminished use of an eye, and suppression amblyopia may develop. Nonparalytic strabismus and suppression amblyopia are treated most successfully in early childhood. The primary treatment to prevent amblyopia consists mainly of covering the fixing eye, forcing the child to use the deviating eye. The earlier it is begun, the more rapid and effective is the treatment. The eyes might be straightened by surgery, but suppression amblyopia will not be corrected. Also called squint. See also anoopsia, esotropia, exotropia. −strabismical, strabismal, strabismic, adj.
