Theoretical knowledge of binocular vision in practical use. Binocular vision conditions. Strabismus - extraocular muscles. Heterophoria, heterotrophia. Instructions about making corrective aids for eye exercises for heterophoria.Development of binocular vision. Anomalous retinal correspondence, eccentric fixation. Determination of angle of deviation. Goals of treatment. Principles of therapy of strabismus - use of prisms, decentration of glasses. Pleoptics, orthoptics.