For the love of all that is good, someone please clarify this for me:

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Knicks

Knicks

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I've looked at a couple of different sources and for some reason I am getting different answers (or maybe it's just me 😳 )

In what directions do the following muscles normally move the eye?

-Superior Oblique (is it "down & out" or "down & in"?)

-Inferior Oblique (is it "up & out" or "up & in"?)

-Superior Rectus (is it "up & out" or "up & in"?)

-Inferior Rectus (is it "down & out" or "down & in"?)



Please clarify, stating what source you used. LoL


Thanks
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According to HY neuro 3rd ed
SR elevates, intorts and adducts
IR depresses extorts and adducts
SO depresses intorts and ABducts
IO elevates extorts and ABducts
 
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^^ thanks


Then why does the diagram in the 2006 first aid (page 345) show the SO moving the eye "down & in" if according to the HY it's down (depresses) & out (aBducts)?
 
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If that is what HY Neuro says, I believe it is wrong. For some reason this does seem to be mixed up in a lot of sources (sup/inf obliques and sup/inf rectus).

Both superior and inferior oblique muscles move the eye in (toward the nose, aDduction), and both superior and inferior rectus muscles move the eye out (toward the temple, aBduction). I've seen it written the other way numerous times, but I've never once seen a chart of the cardinal directions of gaze that shows anything but what I've stated. Thus I have to conclude that the charts are right, and people make mistakes when writing out the descriptions.

Just remember that the obliques pull the eye in toward the nose, and that superior pulls it down, inferior pulls it up.

According to the your nomenclature, that would be:
SR: up and out
IR: down and out
SO: down and in
IO: up and in
 
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BTW, if you go googling this you'll find it both ways. Just trust the cardinal signs of gaze charts. They all agree, that's the way you clinically test the muscles, and that's how I'd answer any question that might come up.
 
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osli said:
If that is what HY Neuro says, I believe it is wrong. For some reason this does seem to be mixed up in a lot of sources (sup/inf obliques and sup/inf rectus).

Both superior and inferior oblique muscles move the eye in (toward the nose, aDduction), and both superior and inferior rectus muscles move the eye out (toward the temple, aBduction). I've seen it written the other way numerous times, but I've never once seen a chart of the cardinal directions of gaze that shows anything but what I've stated. Thus I have to conclude that the charts are right, and people make mistakes when writing out the descriptions.

Just remember that the obliques pull the eye in toward the nose, and that superior pulls it down, inferior pulls it up.

According to the your nomenclature, that would be:
SR: up and out
IR: down and out
SO: down and in
IO: up and in
Click to expand...
Thanks, very helpful.
 
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Sorry, didn't mean to mislead you🙁. I thought that HY was less error prone than FA.
I don't have a copy of the 2006 FA book in front of me, but I do remember that was one of the mistakes in FA and maybe still is. I found this online as a correction to that page in FA (don't know if it's correct) http://rxusmle.com/forums/usmle-step-1/first-aid-2006-errata/, but it sounds like Osli knows what he/she is talking about.
 
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Hi Osli,
could you please refer me to your source, because I was also under the impression from readings that SO, and IO muscle aBduct (away forom the nose), while SR, and IR aDduct (toward the nose).

osli said:
If that is what HY Neuro says, I believe it is wrong. For some reason this does seem to be mixed up in a lot of sources (sup/inf obliques and sup/inf rectus).

Both superior and inferior oblique muscles move the eye in (toward the nose, aDduction), and both superior and inferior rectus muscles move the eye out (toward the temple, aBduction). I've seen it written the other way numerous times, but I've never once seen a chart of the cardinal directions of gaze that shows anything but what I've stated. Thus I have to conclude that the charts are right, and people make mistakes when writing out the descriptions.

Just remember that the obliques pull the eye in toward the nose, and that superior pulls it down, inferior pulls it up.

According to the your nomenclature, that would be:
SR: up and out
IR: down and out
SO: down and in
IO: up and in
Click to expand...
 
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osli said:
According to the your nomenclature, that would be:
SR: up and out
IR: down and out
SO: down and in
IO: up and in
Click to expand...

Pretty sure this is right. When I was learning it last year every book seemed to say something different but pretty sure everyone settled on this.
 
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i say dont worry about ad/abduction of the up&down muscles.

just know 1) which ones work best when your eyes are adducted and which ones work when youre abducted and 2) which ones intort and which ones extort

eyeAnat.gif
 
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DrLizzie said:
Hi Osli,
could you please refer me to your source, because I was also under the impression from readings that SO, and IO muscle aBduct (away forom the nose), while SR, and IR aDduct (toward the nose).
Click to expand...


You are correct. Here is an easy way to remember it.

Just think:

RADical SIN-

Rectus muscles (as in superior and inferior)- ADduct. On the contrary, oblique muscles abduct.

Superior muscles (as in rectus and oblique)- INtorts. On the contrary, inferior muscles extort.

As long as you remember RADical SIN, you can figure it all out from there. Good luck!
 
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ughhhhhh,,,,, this confusion is exactly why I made this thread.


Even here we haven't come up with a definitive answer. WHY IS THIS SO "complicated"? =-/


LoL
 
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Knicks said:
ughhhhhh,,,,, this confusion is exactly why I made this thread.


Even here we haven't come up with a definitive answer. WHY IS THIS SO "complicated"? =-/


LoL
Click to expand...

Look at my post above. RADical SIN. That is 100% correct! All you need is that and you can figure everything out from there. Trust me, I'm an ophthalmologist and I stayed at a Holiday Inn select last night. 😀
 
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Eyesore said:
Look at my post above. RADical SIN. That is 100% correct! All you need is that and you can figure everything out from there. Trust me, I'm an ophthalmologist and I stayed at a Holiday Inn select last night. 😀
Click to expand...

I don't understand the Holiday Inn reference...
 
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At the risk of sounding like someone who wasn't raised in the USA for 25 (almost 26) years, what do you mean by extort/intort?


That's why I just wanted to know it in terms of "up & down" , "in & out"


LoL
 
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You have to be very clear and very careful about exactly what you are asking. If you look at one independent muscle, look at its line of force in a free body diagram, then yes... the obliques move the eye out, the rectus muscles move the eye in.

But eyes muscles are not disconnected from each other. They work in concert, both via brain function and by the physical arrangement of the muscles. They do not work independently. And because of their relative arrangement, and the fact that muscles work better when stretched, a muscle that might pull predominantly in one direction when isolated actually has a different net vector when working as one muscle of a unit.

Thus, why I stated very clearly that you would do well to pay attention to the cardinal points of gaze charts and ignore the text. The cardinal points of gaze demonstrate the primary muscle that is dysfunctional in a real patient. And they all agree. If your eye can't move up and in, then it is the inferior oblique that is dysfunctional, not the superior rectus as the "anatomical description" of its action would lead you to believe. This is because when the eye is directed in toward the nose the superior rectus is short and develops little force, and the medial rectus is anchoring the eye in so that the inferior oblique can't move the eye out. Thus, while the anatomic orientation of the inferior oblique might point up and out, its actual effect on a real eye in a real person is to move it up and in. In a person moving their eye up and in, the superior rectus is contributing very little to that movement; it is the combination of the medial rectus and inferior oblique, and is actually the only movement that can assess the inferior oblique's function.

If you want to keep it in the back of your mind that the anatomic (i.e. isolated) line of force developed by the rectus and oblique muscles is swapped, fine. But remember that in vivo they have the effect as shown in every cardinal directions of gaze chart you'll see, as well as the description I gave above.

The important thing to remember is that in all likelihood on step 1 you will be presented with a clinical situation, and not a description of an eye in a petri dish with one muscle attached. If presented with a patient and in the stem it tells you which direction the eye won't go, or which direction the eye tends to stay, you'd better remember the cardinal directions of gaze and not the anatomic descriptions given by HY neuro, FA (corrected?), wikipedia, or any number of other sources.

Knicks, when you ask what direction these muscles normally move the eye, I think you're getting at what I've written above... in a clinical setting, which muscles have what net effect. The root of the confusion is that the force vector does not match the net movement of the eye. I can't think of one instance where I've been asked what direction the actual force vector pointed, but I sure had a question on step 1 giving me a picture of some dude's eyes and asking about the muscle/nerve deficit, and you don't answer that one via the information provided in HY or wiki.
 
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Knicks said:
At the risk of sounding like someone who wasn't raised in the USA for 25 (almost 26) years, what do you mean by extort/intort?


That's why I just wanted to know it in terms of "up & down" , "in & out"


LoL
Click to expand...

Extort is rotate the top of the eye away from the nose, intort rotates the top of the eye toward the nose. Some muscles have as their primary action, due to the vector of force developed, an intortion or extortion motion. It's a rotation of the eye around an axis going from pupil to back of retina.

As far as step 1 goes you don't need to know or worry about that. Who cares if an eye is elevated and intorted, or elevated and adducted, when the end result is an eye that is "up and in"? Just learn the cardinal directions of gaze (where obliques are toward the nose) and what nerve goes to what, and you can answer any step one question you are likely to have.
 
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Pretty thorough description. Just keep in mind that the little animations they are showing for which way a muscle moves an eye are showing the isolated effect of that muscle. These muscles never get a chance to act alone like that in a clinical setting. Scroll to the bottom and take a look at the cardinal positions of gaze diagram. Had you only read through the page and watched the animations, you'd have come up with a chart exactly opposite of that shown, which is why it is important to know that chart and keep the "primary anatomic functions" of the muscles as a distant thought in your mind. You won't solve a single clinical presentation by thinking through the primary functions... just know the cardinal directions.

This slide set is pretty crude, but does a decent job of explaining why this is so confusion.
 
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Ohh man this has always been a source of confusion; I think the FA diagram good for our purposes. The problem is, all these muscles can have different actions depending on alignment (i.e. direction of the vector). People get very confused with primary actions, secondary actions..etc.. Clinically I think the easiest model is the following:

LR and MR are straight forward.

When the eye is ADducted:
superior oblique is the only muscle that can depress the eye.
inferior oblique is the only muscle that can elevate the eye.

When the eye is ABducted:
inferior rectus depresses they eye
superior rectus elevates the eye.

Anywhere in between ad and ab the elevation/depression are accomplished by a combination the elevators or depressors

Obliques: can also intort (superior) or extort (inferior) - this functions in keeping your vision parallel to the horizontal plane (floor) when you tilt your head to the side.

Diplopias are worse when gazing in the direction that depends heavily on that muscle.

-------------------------------------
 
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Ok,
Great! Then that's waht I am going with for now (according to FA2008)
Thanks!

Eyesore said:
You are correct. Here is an easy way to remember it.

Just think:

RADical SIN-

Rectus muscles (as in superior and inferior)- ADduct. On the contrary, oblique muscles abduct.

Superior muscles (as in rectus and oblique)- INtorts. On the contrary, inferior muscles extort.

As long as you remember RADical SIN, you can figure it all out from there. Good luck!
Click to expand...
 
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Just be warned that there is a big difference between a question asking you what the primary isolated anatomic function of a muscle is (i.e., some lab experiment or "hypothetical" question) and one giving you a clinical presentation and asking for involved muscle or nerve.

If you get a clinical presentation describing a patient that can't move his eye in a certain direction during a basic eye exam, or has an eye that seems fixed in a certain gaze direction, and rely on the above information to determine which muscle/nerve is weak, you will miss the question.
 
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Ok here's a question from the Kaplan Anatomy book with it's explanation:

Asking the patient to adduct the eye and then look down tests:

(A) the SR muscle
(B) the IR muscle
(C) the SO muscle
(D) the IO muscle
(E) the orbicularis oculi



The answer is (C). Explanation:

The superior and inferior oblique muscles are tested by asking the patient to adduct the eye first, then look down (tests superior oblique) or up (tests inferior oblique). The superior and inferior rectus muscles are tested by asking the patient to aBduct their eye first then look up or down.



So, do we use "osli's technique" to answer these types of questions, or the other suggested techniques? 😳
 
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Knicks said:
So, do we use "osli's technique" to answer these types of questions, or the other suggested techniques? 😳
Click to expand...
You use my suggestion (i.e., learn the cardinal directions of gaze), because this question is a clinical description. Kaplan has it right. Had they asked you about stimulating some isolated muscle on an eyeball in a petri dish, or otherwise were very specific in the wording about asking for the direction of force developed by a single muscle ignoring all others, then you might consider the alternative. But that will never show up on step one. If you get a question, it will be like the Kaplan one - a clinical presentation.
 
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hope12 said:
May be this will help:
http://www.tedmontgomery.com/the_eye/eom.html
Click to expand...

Note that on that site the written descriptions for which way each muscle "moves" the eye does not match the cardinal positions of gaze shown beneath. This is because the written descriptions are for the isolated anatomic function of each muscle. The cardinal positions of gaze are the in vivo net result, and are both a clinical description and the key to solving clinical problems.

That site, like many others, is not clear in their wording and thus more confusion ensues. Check out that link I posted earlier... it's crude, but does the best job of showing with pictures and explanations why this difference between anatomic and clinical function exists.
 
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Thanks a lot, osli.

If what you say is true (which it most likely is; you seem confident in your conviction), then this thread has defintely served it's purpose for me. Thanks 🙂


(btw, how'd you do on the step? u can PM me).
 
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osli said:
I can't think of one instance where I've been asked what direction the actual force vector pointed, but I sure had a question on step 1 giving me a picture of some dude's eyes and asking about the muscle/nerve deficit, and you don't answer that one via the information provided in HY or wiki.
Click to expand...

Osli,

I'm looking at the chart now to use for clinical situations, where obliques adduct. You say to use this to answer about a muscle/nerve deficit. Let me see if I understand, using this chart, as I was just taught about the independent functions. I'll use Knicks's nomenclature.

With a CN3 lesion, you would look down and in. (My school taught us that with a CN3 lesion, you look down and out, using the independent functions)

During testing, if the person looks down and out, there is a CN 4 deficit. (My school taught us that with a CN4 lesion, the person would look down and medial due to unopposed IR)

Obviously this doesn't change that with a CN6 lesion, you can't look lateral (since this remains the same using either technique).

Is this what you mean by how they would ask, Osli? If not, can you please give some examples? I would love to get this straight in my head.

Thanks so much!
 
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Samples🙂
http://www.dartmouth.edu/~dons/part_1/chapter_4.html
4-1. Which muscles would be active in the right and left eye when looking up and to the right?
Answer 4-1. In the right eye the lateral rectus and the superior rectus would be the prime movers, while in the left eye, the medial rectus and the inferior oblique would be most active.
4-2. Which muscles would be active in the right and left eye when looking down and to the left?
Answer 4-2. In the right eye the medial rectus and the superior oblique would be the prime movers, while in the left eye, the lateral rectus and the inferior rectus would be most active.
 
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This is so confusing, I think this may simplify it.

Think of the muscles primary and then secondary and tertiary actions.
AND use the RADical SIN posted from eyesore earlier on.

RADical SIN

Rectus - ADDuct >> so obliques ABDuct
Superior - INtort >> so inferior EXtort

Adding to this

RECTUS primary function is MOVEMENT
OBLIQUES primary function is ROTATION and their movement is OPPOSITE to their name. Superior obliques >> depress, Inferior obliques >> elevate

SO
Superior rectus
1. movement - elevation (because it is superior and a rectus)
2. direction - ADDuction (because it is RADical)
3. rotation - (superior) so INtortion

Inferior rectus
1. movement - depression
2. direction - ADDuction
3. rotation - EXTorsion

Superior oblique
1. Rotation - INtorsion
2. direction - ABDuction
3. movement - depression (its an oblique so its movements are opposite)

Inferior oblique
1. Rotation - EXtorsion
2. direction - ABDuction
3. movement - Elevation

lateral rectus >> looks laterally
medial recuts >> looks medially

in simple combination the key movements of SR & IO look up and midline - I cant explain why the direction is opposite when they act in "yolked movements" but in realty to look up and out is a combination of SR & LR, so how Yolked movements fit I am not sure except there has to be relaxation of the opposite muscle in the opposite eye http://www.tedmontgomery.com/the_eye/eom.html

BUT I find it easier to think about which muscle acts as above and if you took that muscle out of the equation due to a lesion the effect is then self explanatory.

Hope that helps.
 
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SINRAD is for isolated eye movements,

However, For your superior and inferior muscles:

Maximum movement of obliques is when the eye is adducted

Maximum movement of recti is when the eye is abducted.

Ergo, a right SO lesion will result in the eye being elevated. And the hypertropia will be worst on left gaze and worst on head tilt to the same side.

A lot of the literature out there is individual eye movements... But you should look at climical eye movements. Any ophthalmology text wil have the correct info.
 
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2Aspirin said:
Osli,

I'm looking at the chart now to use for clinical situations, where obliques adduct. You say to use this to answer about a muscle/nerve deficit. Let me see if I understand, using this chart, as I was just taught about the independent functions. I'll use Knicks's nomenclature.

With a CN3 lesion, you would look down and in. (My school taught us that with a CN3 lesion, you look down and out, using the independent functions)

During testing, if the person looks down and out, there is a CN 4 deficit. (My school taught us that with a CN4 lesion, the person would look down and medial due to unopposed IR)

Obviously this doesn't change that with a CN6 lesion, you can't look lateral (since this remains the same using either technique).

Is this what you mean by how they would ask, Osli? If not, can you please give some examples? I would love to get this straight in my head.

Thanks so much!
Click to expand...

CN 3 lesion should be down and out since you have CN 6 and 4 unopposed
CN4 lesion should be down and in since you have CN 3 unopposed
 
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For anyone looking for a simple explanation.

Anatomically, the SO moves the eye down and out. The IR moves the eye down and in. Since they both move the eye down, in order to test for SO in isolation, neutralize the effect of IR by adducting the eye in. Thus, by moving the eye down, the net effect is that of SO. Cardinal gaze is a clinical tool that shows which direction to move eye to best test for SO (down and in). This does not mean that SO moves eye inwards. The inward movement is simply there to neutralize the effect of IR so that SO can be tested in isolation. Vice versa when testing IR by neutralizing SO.

Hence, 3th nerve palsy gives an eye that is down and out (only superior oblique and lateral rectus are functional)
4th nerve palsy gives an eye that is up and in (net result of absent superior oblique. Patient has blurry vision when moving eye down and out and compensate by tilting head).

Explanation consistent with the Kaplan question posted earlier, the anatomical eye movements, the clinical utility of the cardinal gaze directions AND clinical correlations.

Hope this helps someone.
 
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100% agree with Cranial Nerve 17. Cardinal Gaze isolates the actions of individual muscles, but the positions don't necessarily correlate with those actions!
 
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Cranial nerve 17 said:
For anyone looking for a simple explanation.

Anatomically, the SO moves the eye down and out. The IR moves the eye down and in. Since they both move the eye down, in order to test for SO in isolation, neutralize the effect of IR by adducting the eye in. Thus, by moving the eye down, the net effect is that of SO. Cardinal gaze is a clinical tool that shows which direction to move eye to best test for SO (down and in). This does not mean that SO moves eye inwards. The inward movement is simply there to neutralize the effect of IR so that SO can be tested in isolation. Vice versa when testing IR by neutralizing SO.

Hence, 3th nerve palsy gives an eye that is down and out (only superior oblique and lateral rectus are functional)
4th nerve palsy gives an eye that is up and in (net result of absent superior oblique. Patient has blurry vision when moving eye down and out and compensate by tilting head).

Explanation consistent with the Kaplan question posted earlier, the anatomical eye movements, the clinical utility of the cardinal gaze directions AND clinical correlations.

Hope this helps someone.
Click to expand...
awesome. Thanks
 
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