Fig 3. Inferior rectus muscle. The inferior rectus muscle courses at an angle of 23° to the medial wall of the orbit, giving depression principally in abduction (C) and extorsion in adduction (A). In the primary position (B) the main thrust of the pulling power is medial to the center of rotation, causing slight adduction action in addition to the cyclovertical action. (Parks MM, Parker JE: Atlas of Strabismus Surgery. Philadelphia, Harper & Row [in press]. Courtesy of John E. Parker)