Simulated superior oblique palsy.

Accurate interpretation of the Bielschowsky head tilt phenomenon, as incorporated in the three-step test, relies on the assumption that the patient has a palsy of an isolated cyclovertical muscle. Other causes of hypertropia, including restrictions, associated horizontal deviations, previous strabismus surgery, and symmetric oblique overaction, if not recognized, may lead to erroneous diagnosis of superior oblique palsy with the three-step test. Seven representative cases are presented.