Eye Movements Produced by the Superior Oblique Muscle

Introduction The action of the superior oblique muscle has been inferred from anatomical relationships, from oculomotor defects produced by III or IV nerve damage, and from ophthalmotropes. With few exceptions1,2there is general agreement that when the eye is adducted the superior oblique muscle acts to depress the eyeball and when the eye is abducted, it acts to intort and abduct it.3-8Nevertheless there have been few experimental studies of superior oblique muscle action in the intact mammal or in humans.1-3,9This paper presents the results of such a study. It shows that eye movements induced by isolated contraction of the superior oblique muscle fit closely with those predicted from the anatomy of the globe and orbit. Methods and Materials Seven cats and one monkey were studied. In each case the trochlear nucleus and/or trochlear nerve roots were electrically stimulated to produce contraction of the contralateral superior