so what's the difference between the clinically-relevant eye movements versus the anatomical function of eye muscles a few years ago I published a video regarding eye movements and cranial nerves and it may be confused people specifically the difference between the cardinal positions of gays and the anatomical functions of the eye muscles this confusion stems from this diagram where I said that this represented the actions of the eye muscles what I should have clarified that this schematic represents the positions that a person is asked to look to test the various eye muscles these are called the cardinal positions of gaze in other words with the exception of the horizontal rectus muscles the direction the eye is pulled by the action of a muscle do not correspond to the diagnostic positions of gaze in which the eye is placed to test the strength of that muscle so keep in mind that isolating and testing eye muscles clinically is different than their anatomical actions so let's go through this muscle by muscle the superior oblique has a primary action of in torsion a secondary action of depression and a tertiary action of a deduction this results in a movement that is down and out the inferior oblique has a primary action of extortion a secondary action of elevation and a tertiary action of AP duction which results in a movement that is up and out the inferior rectus results in a primary depression secondary extortion and a tertiary a deduction resulting in a movement that is down and in superior rectus results in a primary elevation secondary in torsion and a tertiary a deduction resulting a movement that is up and in in a clinical setting you want to change the visual access and isolate each muscle and so the diagnostic gaze positions for the recti and oblique muscles is in the direction where the muscles act as pure vertical movers for their obliques this means having the person a deduct on that side or look medially and for the recti muscles this means having that person EB ducked or look laterally this is where the schematic for the cardinal positions of gaze come in or asking a person to look medially and down tests for strengths and deficits in the superior oblique muscle positioning the eye up and in tests and isolates the inferior oblique looking up and out tests the superior rectus and looking down and out tests than fear erectus and finally the medial and lateral rectus are tested simply in the direction in which their muscles pull the clinical relevance of this difference from anatomical movements can be demonstrated in someone who has weakness of the superior oblique muscle these people will have difficulty looking down and in or looking to the tip of their nose on the affected side additionally these people may tilt their head to the opposite side of the weakened superior oblique muscle in order to minimize the effect of the weakened muscles this is known as an ocular torticollis