 Let's go ahead and get started. Welcome to, this is pediatric ophthalmology style at Grand Rounds. We're gonna do case presentations. And first up is Dr. Dries, who's lately become quite the expert on superior oblique dysfunction, surgery and everything associated with it. He's gonna share some of the wisdom that he's gathered. Thank you, Bob, and good morning, everyone. This morning, I'm trying to present something that will interest you with quite a bit of information and fairly quickly. So, what if I told you that the superior oblique muscle was not just one muscle, but rather two? And indeed, it kind of is. There are muscle compartments in multiple extraocular muscles. And this morning, I'd like to talk about the compartments of the superior oblique and what that means clinically for diagnosis and surgical management. Thank you to Dr. Joseph Deemert, UCLA, and Steve Archer, the University of Michigan for helping me with figures and multiple discussions over the more recent years. Here, you're looking at the histology of the superior oblique muscle belly with multiple cuts starting posteriorly and then the cuts march anteriorly. And the two colors correspond to two branches of the trochlear nerve. This green color innervates here, the purple-ish color here. And here's a reconstruction of selective, separate innervation of the two compartments of the superior oblique. Separate innervation makes sure that it has a totally separate oblique. Yes. So, what does that mean clinically for diagnosis and surgical management? Well, we do need to talk just a bit about motor physiology of the superior oblique. As we all know about the axes of rotation, the superior oblique is an in-torter, an abductor, and a depressor. So, here are a few diagrams. This is the vertical axis about which the eye rotates horizontally that gets you oriented as to the position of the superior oblique tendon with regard to that axis. And you'll have to think about the other axes, sagittal and horizontal as well. This is in primary gaze. And it makes sense that this muscle has those three functions. What about in down gaze? Well, it does change a bit. It's a better in-torter, an abductor in down gaze. And that's in large part because, simply put, the muscle just pulls harder. But the superior oblique does have this unique anatomy we all know with an origin at the apex of the orbit coursing anteriorly and curving around the trachelea and then tendon fibers fanning out in the globe. And in down gaze, here, actually here, this is the eye in down gaze. You can't see the cornea very well. And it's kind of hard to understand why the muscles have better in-torter and abductor. So, let's view the eye in down gaze 30 degrees forward. If you saw the movie, The Matrix, they were fighting and they would freeze and then the camera would pan over to a different perspective. That's what this view is like here. So, the eye is in down gaze. Look what happens to the relationship between the belly, the superior oblique, and the tendon. This is more or less perpendicular. Here, it's more acute. And if you look at the vertical axis, you can see the position of the tendon has changed with regard to that axis, making it a better abductor in down gaze. And the tendon is more at the equatorial position, giving it better in-torsion in down gaze. The contribution from this unique anatomy is only about five to 15% increased in-torsion and abduction. Mostly, it's that the muscles just pulling harder. So, what does this mean clinically? Well, what's it like to have torsional diplopia? This is what it's like to have torsional diplopia. This is a 55-year-old photographer who supplied this photoshopped photo of what it's like to walk down stairs at an apartment complex. And I would just like to show you in this diagram the compartments of the muscle. There's a lateral compartment of the superior bleak and a medial compartment. The lateral compartment, its tendons insert on the posterior fibers of the tendon and the medial compartments inserts on the more equatorial anterior fibers. So, the lateral compartment has more depression and the medial compartment has more in-torsion. The case here is a lady mainly with a hemorrhage with tons of torsion, okay? So, you think maybe this is a selective medial compartment peresis. One could speculate. She has lots of torsion, eight degrees in primary gaze, much more in down gaze, 15 degrees. Really makes sense that those anterior fibers are affected, right? And the medial compartment. And look at her vertical deviation. It's really not that big. It's really quite small and there's not much incompetence in down gaze. So, the posterior fibers of the tendon probably are less affected. Probably the lateral compartment is less affected. So, what surgery would help her because she's suffering? Prism isn't gonna work. Well, let's go back to the 20th century and talk about the Herata Ido procedure. Initially devised by Japanese Dr. Herata, Dr. Ido just to anteriorize the front tendons of the superior bleak but later fells modified it by splitting the tendon and transposing these fibers temporally and anteriorly on the globe, giving them a better mechanical advantage to in torsion. How did it work? Well, quite well. Her extorsion is two in primary gaze, six in down gaze. She still has her hypertropia. Initially she fused two weeks out but three months later she did have trouble controlling her diplopia again, especially in down gaze. Luckily, a small amount of vertical prism and she was fusing and she liked spectacles in the first place and she's happy. So, does she have a selective medial compartment superior bleak parisus? One can speculate but we really don't have dynamic MRI that will really tell us this in these patients at this point. Let me just talk about one more case. I think this is bilateral and maybe even a bilateral medial compartment trochlear parisus. A 60 year old female director of medical directors at the University of Utah, torsional and vertical diplopia with a small head tilt going back to the teenage years but a worsen recently after she had cataract surgery which often happens with clarity of vision in patients with pre-existing strobismus. She had diplopia when driving and when reading. Let's look at her exam. Bit more complex than the last one but look at how much torsion there is. 15 degrees in primary gaze, 16 degrees in down gaze. That is a lot of torsion. And let's look at her exam. Again, a hypertrophy that's not large without much incompetence which would argue that the posterior tendon fibers at the superior bleak and the lateral compartment probably are not as affected. She does have a V-pattern and an esotropia in primary gaze. She doesn't have classic three-step Parks Bielszalski testing for superior bleak parisus but I think she probably has a mass bilateral superior bleak parisus. When patients are this complex you got to break down the deviation. You got to treat their extortion, their esotropia with their V-pattern and their hypertropia. A superior bleak tuck might have been a good choice but it chose not to do that because she had such little incompetence of her hypertropia and her hypertropia was small in down gaze. So instead for her hypertropia a contralateral inferior rectus recession is my procedure of choice, the yolk muscle of the predic superior bleak. She also has the esotropia with the V-pattern. She needed a media rectus recession, one half tendon with infra placement for the V-pattern but keep in mind when you transpose recti muscles you induce torsion and if you infraplace the media recti you're going to make her extortion worse. So she had a bilateral herata edo. Bilateral with the goal of creating 15 to 20 degrees of mechanical encyclotorgen under general anesthesia which we can do with a Mendez ring. The refractive surgeons know what that is and the sturbismus surgeons are beginning to learn about it because you can mark the lid, mark the limbus, do your surgery, change torsion and measure how much you got mechanically. There are other ways to do this but this seems to be the most convenient easiest for me. So how does she do? She was fusing in all gaze positions except for extreme down gaze. Her extortion was five degrees in primary gaze, five in down gaze. So she did very well and mainly the point here is could she have a bilateral medial compartment superior oblique peresis? So what if I asked you, does the superior oblique muscle have two compartments? Well you'd probably say yes. Thank you.