deviation of the visual axis of one of the eyes from the common point of fixation, leading to a loss of binocular vision. Two types are distinguished: concomitant and paralytic strabismus.
Concomitant strabismus, in which the deviating eye always follows the movement of the other eye and the angle of divergence of their visual axes remains constant, is observed predominantly in children (up to 2 percent). Its causes have not been conclusively elucidated. Strabismus may be accommodative, owing to anomalies of refraction and disturbances of eye accommodation, or nonaccommodative. Accommodative strabismus disappears upon administration of drops of atropine in the eye and use of corrective lenses: nonaccommodative strabismus is distinguished by extreme persistence. Strabismus may be constant or periodic, unilateral (when only one eye deviates) or alternating, and convergent (when the deviating eye moves toward the nose) or divergent (when the deviating eye moves toward the temple); the eye may simultaneously deviate upward or downward as well.
In approximately half the cases of concomitant strabismus some decrease in acuity of vision is noted in the deviating eye. The treatment of nonaccommodative strabismus is manifold, employing both various exercises for the eyes on special instruments (synoptophores, amblyoscopes) and operations directed toward weakening the stronger eye muscle or strengthening its antagonist.
Paralytic strabismus originates with paralysis of the oculomotor muscles as a result of disease of the central nervous system (infection, hemorrhage). It is characterized by limited mobility of the paralyzed eye, double images, and a different deflection angle of either eye. Treatment is directed at the disease causing the strabismus; sometimes vision can be restored by special operations on the eye muscles.
M. L. KRASNOV