Clinical testing extraocular muscles tutorial 

You are most welcome! I am happy it was helpful.

@@TheNotedAnatomist very helpful..God bless you

Glad it was helpful!

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Glad it helped!

😂

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You are welcome

Any physical exam from a general practitioner or neurologist

yeah i have the same question... either we're dumb or ppl r just memorizing the rules and not understanding this point

Ok so we r just dumb, i thought about it and realized the mistake me and u were making (i think) KEY POINT: there is a difference between muscle action depending on the STARTING POSITION of the eye. Example: RIGHT EYE: Look straight then look (in one motion) to the top right corner of your eye, that's inferior oblique doing the job (PLUS superior rectus because it also acts on the Y axis in bringing eyeball up) Now, RIGHT EYE: look alll the way to the right, you just ABducted using your lateral rectus, NOT your inferior oblique. Now, go look back at the vectors in his video for testing the superior rectus, you will see that because the eye is ALREADY ABducted using LATERAL RECTUS, the inferior oblique due to its positioning CANNOT elevate the eye along the Y-axis as it previously could when the eye started at NEUTRAL position (it can only rotate the eye which as he says in the video is hard to see). Effectively, the SUPERIOR RECTUS muscle is the only muscle left that could function in the ABducted position of your right eye for LOOKING UP along the Y-axis. Therefore if a person cannot raise their right eye from the ABducted position, it must be due to SUPERIOR RECTUS dysfunction because that's the only available muscle able to make the eye look up from the ABducted position given you ELIMINATED the function of the other muscle (inferior oblique) that can make the eye look up. Hope that helps all the other ppl who r dummies like me out there (or just have another way of thinking =))

Wow this is actually ground breaking explanation!!! thanks @@crymore7

When 2 muscles are both responsible for elevating the eye clinicians figured how one muscle could be tested without recruiting the other muscle to elevate the eye. For example, both the SR and IO elevate the eye. when a patient abducts the gaze of the eye is parallel with the SR muscle. In this way when the patient looks up the only muscle elevating the eye is the SR. The IO muscles vector pull is perpendicular to the gaze of the eye and thus only acts on the z-axis to extort the eye.

@@TheNotedAnatomist so a better way of understanding it is to say that the gaze of eye is made PERPENDICULAR to the vector pull of the muscle(IO)that also causes the same action as muscle that we are testing(SR) instead if saying the gaze is made parallel to the muscle(SR) being tested .i know it sounds a little complicated but it clears the doubt. The focus of the test is to make the gaze perpendicular to the IR rather than Parallel to the SR. And in actual measurements those two vector axes are not perpendicular(SR vs IO on horizontal plane ) but for practical/clinical purposes making the gaze parallel to the muscle being tested( which is perpendicular to the mucle not being tested but produces the same action) gets the job done and is simpler to understand.

In more simple(but not simplest) terms , in case of SR muscle test , when the eye is in abducted position even if the IO gets the nerve signal and contracts it can't produce any movement in horizontal axis( elevation /depression) so the only muscle that can produce such action is SR.

+ohoney jones To test the lateral rectus muscle all that is required is for the patient to abduct the eye. To test the superior rectus muscle the patient must first abduct the eye then elevate it. In this way, the superior rectus muscle is isolated from the inferior oblique muscle (the other muscle that elevates the eye). Does that help?

Just an additional info, it could be the clinician also want to know the intorsion-extorsion movement of the eye while doing a certain eye movement that is why it need ti abduct it first.

+Supratim Karmakar Hi Supratim, yes the superior rectus does elevate the eye in the abducted position. As well, the inferior rectus depresses the eye in an abducted position. However, in the natural state, when the eye is looking forward (neutral position) the superior rectus muscle elevates and adducts the eye (look up and in). This video tutorial discusses the clinical testing of extraocular muscles and CN's. This video discusses the anatomical movements of the muscles (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-u3BcgOIjbGA.html)