 So this is not the most exciting lecture ever. It's actually something I think about a lot. And something I always worried when I was a resident that they were going to ask on OCAPs. But they didn't really ask too many questions on this, on OCAPs or on the boards, as I recall. But I remember reading those books and being totally haunted by a lot of these tests and questions and things. So a whore-opter is the space or the points in distance that fall exactly on the same part of the phobia at the back of the eye. So your phobias have to be completely lined up on the same image there to get one binocular image. Panum's fusional area is a little bit bigger than the. So a whore-opter is like the physical. It's more of a theoretical point or theoretical points that line up that if you look at them, your phobias line up exactly the same. Panum's fusional area is a little bit bigger than that because when your eyes aren't perfectly lined up together, you can still see one image within Panum's fusional area. And that's what gives you stereo, too. So the images are a little bit different. If you look at something, it's a little bit different from one eye to the other eye. But your brain can fuse it together and make it in stereo. So the stereoscopic image that you see, you can get that, is a little bit bigger than Panum's fusional area. So it's essentially the points in space that you can see that you can make into one image with both of your eyes working together. This is kind of what I was talking about. So your brain is what puts it together, that binocular image for a normal visual experience. They had to be similar in size and shape, which is something you think about in cataract surgery because you don't want to make somebody really anisomatropic or you cannot put that together, something we called anisoconia. What that is is a little bit different in each person. But a few diopters can really throw of somebody who hasn't been that way before can throw somebody off. And that is worse when you're thinking about glasses or things. That's why we cannot put unilateral cataracts in glasses because the prescription would be too big in one eye. You'd have to put a plus 15, plus 20 in one eye. And if you looked out of that eye, the image would be bigger than this one. You can put a kid in that, and they will learn to do it. But then they will have to be that for their whole life. So fusion in areas near the phobia tolerates very little dissimilarity between the images. That means that that's because you've got your good 2020 vision right there around the phobia. You can tolerate a little bit more in your peripheral vision because your vision isn't really as good. So you can pull those in together a little bit better than you can something that's right center in the center of your vision. These are artificial subdivisions that they talk about in the book. Sensory fusion is the top of graphical relationship between the retinas, kind of what we're talking about with Panam area, where images on corresponding retinal parts come by before a single image. So that's actually when you're lined up perfectly. Motor fusion is what your eyes do to attain fusion. So it's what we see when you put up a prism in front of your eye and you can start fusing to pull it in together. Your eyes want to work together, which is why stirbizma surgery usually work. It's not perfect. We do it about usually when we do stirbizma surgery, move things back, and it usually works because usually if somebody is a fuser or if you can get them close to fusion, their eyes kind of lock it in. So whereas when they're way off, it's a lot harder to do that. Stereopsis is what I was talking about before. We test that with our monocular stereo vision. Yeah, it's a fine thing. Derision isn't that much different if you look out of one eye or versus the other eye. But, and like I said, it's slightly wider than Panam's area and adds a little bit of a unique quality to your vision. We test that using those little books in clinic. As you could see, how do they work? You can tell if you look without the glasses. Number one on the top is the one that pops out. If you look, it's actually giving a little bit different image to your right eye versus your left eye, giving that sensation of stereopsis. And these tests in the book, they get progressively harder. You have to have good visual acuity in each eye though to have stereo. So it's sometimes a way to test fakers in your clinic if they have stereo, which we see quite a few other peds. You have to have good vision in each eye to have good stereo. So you got to get all the way down to 40 seconds, the end of that TITMAS testing. You have to have 20, 25 vision in each eye. Which is kind of what we were talking about before in terms of you don't tolerate very much difference between the two eyes when you're talking about fusion, macular fusion. So if the vision is that the image is pretty blurry in one eye, you're just not going to be able to fuse that together. In peds clinics sometimes we'll use a stereo test that's, you know, you don't have to put the glasses on. This is called a Ling and have them pick these pictures. It's harder to see these without the glasses. Whereas, you know, you can kind of fake with these if you don't have the glasses on. You can at least see the first three or four pretty clearly without the glasses. Sometimes it could be a little better, sometimes the kids are a little better, but it doesn't nearly test the same amount of the cutity of stereopsis. But in kids you're often just looking for gross stereopsis anyway. What is gross stereopsis? That's, you know, pretty, you know, these test how good your stereopsis is, how fine it can get. The gross stereopsis is this fly. We want to look and see that they kind of pull it up. If they go straight for it, just touch the book. We say they fail. It's kind of hard in kids sometimes. Usually if they scoop up the wings of the fly or if they really try to grab the top of the wings we know that they can see it. But when they go right for it and just grab at it. Because even if you can look, even with one eye it does kind of give a funny image. It almost looks kind of like you're seeing in stereo but you aren't truly. So sometimes that can be a little bit hard to tell on kids. But people with peripheral fusion who have a little bit of stirrismus and not as great a stereo, yeah. We want to see if they have gross stereos. So we'll test this. Which is quite a bit different than that first circle I think is 400 arc second or 800 arc seconds. So you're talking about 800 arc seconds versus 3000 arc seconds. The difference between their stereo from that first dot versus the fly. People are often worried if you don't have, and binocularity is what we're trying to get with stirrismus surgery, right? The earlier we operate some studies say if you don't operate to fix stirrismus but for like three years old you're never gonna get stereopsis. Those studies are kind of hard to do because you can't really separate out the kids who develop stirrismus versus the one who never had stirrismus. But this is what we're trying to get in kids when we do surgery early. And sometimes we get it and sometimes we don't. And people are always worried, well, my kid had death perception. Yeah, you'll still have death perception because death perception is not stereopsis. After about 10 or 20 feet, most of your death perception is on an ocular cue so you're not even using stereopsis. I always kind of wonder like, I think probably the super elite athletes, like those tennis players and stuff probably have super, super stereo. Like they probably are able to see that spin, you know, and the baseball players and things like that. I think they probably have really, really good stereo. Maybe it's gonna hold them back from being an elite athlete, but other than that, not having stereo, I don't think it's gonna hold you back much. You know, there are lots of other things that we use to gauge death perception, you know, object overlap, relative size, highlights and shadows, perspective. You know, stereopsis is purely something we kind of test with those tests. Yeah, I think it does make it a little bit, it does improve your vision, but it's really only when you get kind of closed. So not having stereopsis does not mean you're not gonna have death perception. So much of your brain has vision radiations running through it. So, you know, any kid I see who has any neurologic problem is much more likely to have strabismus. I mean, your eyes are at the front of your brain and everything's interpreted at the back. So, you know, and you learn about that where the visual radiations run and can tell us about strokes and insults to the brain and things. The optic radiations decussate at the chiasm and that's really essential for monocularity. People with albinism, you know, all the fibers cross, whereas, you know, most normal people, those nasal, just the nasal fibers cross. That means people with albinism don't have normal monocularity, but it's also the basis of the test that Creole does. So he, you know, can do a VEP and see how his response is different in albinox and that was really kind of the work that he did that got him on the map. But some kids that were wondering if they have albinism, especially the one, because they can't sit in an OCT very well, A and B, they've gotten a stagmus, their OCT isn't that good. So we're, you know, trying to look at their phobia to see, but we can shine a light and then record the electrical activity at the back. That's what a VEP is and their response is different than normal people. So visual information from corresponding retinal area runs through the lateral genicular body and is all interpreted at the back in the visual cortex. This is in your book, but I never have seen a test question about it in my training. Those magnostellular cells within the lateral geniculate nucleus are represented with peripheral retina. They're more sensitive to moving stimuli and insensitive to color, whereas the parvocellular ones are primarily in the phobia. They tell more high-resolution information about borders and color contrasts and they're important for seeing detail. The last cells there are less understood, maybe help you see the color blue a little bit better. When you're born, your phobia is covered by multiple cell layers at birth, which is problematic when you send kids for VEPs when they're really young because they don't really have a normal phobia yet. Also when you're looking in there and I've fed for albinism stuff, their phobias are not fully developed, but they develop pretty quickly. The photoreceptors then move around after birth and really all the cones localized to that phobia area. During the first two years of life, the white matter violinates and then neurons in the lateral geniculate buclet increase in size until your brain and eyes keep developing until you're about 10. You get an abnormal visual experience, abnormal binocularity. If you have visual deprivation to under both eyes, anti-symmetropia, astromismus. In, they've done studies, so if you close one eye in adults or in monkeys, things change and things grow and change. One thing that happens is that their eye starts growing more myopic. Sometimes we can tell that in kids that with amblyopia that sometimes kids have a little bit of a cataract and we're wondering if that's really visually significant or not. If you check their prescription and they're more myopic in that eye, it suggests that they are more amblyopic because of that. The other thing is that the lateral geniculate nucleus will shrink a little bit on the side of the decreased vision. And that's what they're saying here on this bottom thing. So people have such a hard time with amblyopia. They don't understand why they still can't see what the glass is. It's a brain problem. So what is amblyopia? It's a decreased vision in one eye that we can't see anything that causes it. So we're assuming it's the brain. So they've actually done studies where they look at kittens or monkeys where they'll sew one eye shut and their lateral geniculate nucleus is thinner on one side. So your brain actually does not develop, even physically they can tell the size is different in an eye that is amblyopic. And that's what it's saying here. That if you close one eye, one the lateral geniculate nucleus will shrink and then the open eye starts growing into that area, which is kind of interesting because that eye still is only 2020. So it's not like it gets, it's like a bionic eye or anything, but it starts to occupy that space but it's still thinner on the side of the amblyopic eye. So amblyopia is just that the brain does not interpret that information well and we can actually see that. And the only way to fix it is to force the brain to work by patching or penalizing the good eye. Yeah, they've shown that blood flow and glucose is lower during stimulation of the amblyopic eye, it's just not wired as well. And the only way to wire it better is to catch it early and force it to work. And that's why binocularity is not that as good in those kids with amblyopia because those binocular centers within the lateral genically nucleus just don't form as well. The critical period is that period where you want to catch people, catch kids, where you can actually reverse amblyopia. In the studies they've done, it's where they can unsuture that eyelid to make the vision better. And after that critical period, if they treat that or reverse the occlusion, they cannot make those columns within the lateral genically nucleus re-expand. So yeah, so that is what amblyopia is. It's reduced vision caused by a bad brain because the brain hasn't learned how to see. You have to learn how to see and so if one eyes closed, you're just not gonna learn how to do it. And when you have that, you're much more likely to develop strabismus. But strabismus is something that can cause it. Anisomatopia that can cause it. Much more farsighted than nearsighted. And hi, bilateral refractive errors. So bilateral amblyopia or what they say, amatropia. Why does amblyopia cause by anisomatropia? Sorry, it can be caused by optical defocus that can be from anisomatropia. If you have amblyopia for anisomatropia, meaning that your eyes are just two different shapes, so kids with hyperopia, if they're nothing in this eye and a plus three in this eye, if they are just looking far into distance, they're just gonna focus this eye and leave this eye three diopters unfocused. So that is why they develop amblyopia, just because this eye is always blurry. If you cover this eye, they will focus it, but they're not doing that normally, so their brain just isn't usually using that. So if they do have amblyopia from optical defocus, it's much easier to treat than strabismus. If you just put glasses on these kids, most of them will fix with just the glasses. And even up to like age 13, and she showed in up in PEDIC studies that they can get better. It doesn't usually develop during the first year of life, may not develop until they're a little later, whereas strabismus is much harder to treat. Why is that? Because their phobias aren't lined up. It's also because of optical defocus. They're not focusing that eye to make it clear. If they're turned a little bit in the right eye, they're looking with this side, this side is just not even gonna focus. They just kind of, they have abnormal accommodation usually, which develops over time because they're not using it. This develops earlier is much harder to treat. You know, if you do have strabismus, your brain adapts to get rid of that second image. So it's an adaptation thing that's good, but it's bad because you start to lose vision. So your brain just turns off one eye. Patients with strabismus who develop the strabismus early and have normal retinal correspondence, meaning their brain is wired so that the retinas should line up together. They learn to suppress or turn off one image. It can be facultative, meaning you, it's not all the time. Yeah, they don't always have, they don't always have, they are not always suppressing. So yeah, like an XT, they're often using their eyes, sometimes it will turn out. So they're not suppressing 100% of the time. They have that in there, but it's only happening when that eye's drifted out. How do we treat it? We put them in glasses, we treat their amblyopia of patching or atropine, and we try to align them as early as we can with strabismus if glasses don't work. Can be a little bit troubled, hard in people who fuse, which is why strabismus surgery doesn't work as well in them because we just get them close and they don't put in that fusion. Anomalous retinal correspondence means that just the way their brain is wired is with the phobia of one eye lined up with not the phobia of the other eye. It's an adaptation in people who have strabismus to get some amount of binocularity. Sometimes these people, and this is kind of what they like, can't ask about and test some things. Sometimes after surgery, if you get them straight, they will still have strabismus because even though straight is normal for most people, it is not normal for them because their phobia in one eye and their pseudophobia in the other eye are not lined up. But if they have, and I've only had this happen once and the kid had dyplopia for like six months and then I went away, but yes, it usually goes away. These are the really confusing tests that you read about in the books. I've never actually had a question on these, but a red glass test in a person who has harmonious anomalous retinal correspondence with an esotropy, you can see in that right picture that their phobia is lined up with their P, their pseudophobia. So in a normal person, their phobias would be lined up in this person, their right eye is crossed. So their brain has learned that, or has adapted so that they're trying to get some amount of anocularity when their phobias lined up with their pseudophobia. And that is why when they look at that red light, they blend that red light in the right eye with the left eye, and it becomes a pink light. Whereas when you fully correct their esotropy and put the image on the true phobia, they see diplopia. Unlike non-harmonious, where they kind of have that pseudo fusion or just that very peripheral fusion when you correct a little bit of the esotropia. When you correct all of the esotropia, they get diplopia. When you correct some of the esotropia, they can kind of fuse it. But walking around there either have diplopia or they have suppressed the image. Whoopsie. So with this red filter test, and somebody who has NRC or normal retinal correspondence, if they have an exotropy, they have cross-topopia. And that's where they put a red filter in front of one eye and tell you where the red image is or where the red light is. Whereas somebody with esotropia is gonna have an cross-topopia. We're four dot testing is something I do quite a bit. Just trying to figure out what people's visual experience is. It's kind of hard in kids sometimes. You put the red lens over the right eye, the green lens over the low left eye, the right eye sees two reds, the left eye sees three greens. But if they're fusing together, they should be see four lights. It can be hard in people who are alternately fusing because they'll say I see two or in people who can kind of alternately fuse. In general, that's the classic teaching. Two, if they see two or three, they're suppressing one of the eyes and it depends on which way you put those glasses on. If you see four together, if you see four together, they're fusing. You can also use the same crossed or uncross. If they're seeing that the lights crossed this way, they have an XT. If they're uncrossed and they have an ET in there. Sometimes when people's eyes look straight, yeah, they're having some kind of funky thing going on where you can't really figure out if they can use the rest together. So it can be really helpful to use this. They're seeing five lights. Yeah, they've got either double vision or they're alternately suppressing. So that's like, if they're ET and they're looking out of this eye, they're gonna see the two red. But then if they flip behind the glasses, they're gonna tell you to see that. So they don't necessarily always have to plop you if they see the five lights, only if they see them all together. But sometimes they'll say three, two, three, two. Monofixation is when people have some amount of peripheral fusion is kind of when they have a little bit of strabismus and they're trying to get some amount of binocularity, these people will suppress a distance. So they'll say, oh, I see two rights when you're looking far away and then when they come up close, they see four. This can be, what's up my next slide. These are people who have peripheral fusion with the central scatoma. So these are the people who come in and they're like 2040 and one eye and 2020 and the other eye and you can't figure out why and you dilate them and they've got the same prescription between the two eyes. And you do a cross cover test and you can't see anything and then yeah, they either have a very small misalignment that you can't see or they've had some kind of astropotopia that's resolved by itself. These people have stereo, that's why they have the monofixation syndrome but it's usually reduced, it's not normal. So they can maybe see a couple of the dots popping up and they can maybe see the fly but they can not get all the way down. Ambuliopia is common, they usually have a little bit and more of that is because their eyes are not lined up and this can be a little harder. It's harder to treat usually than anything with anti-symmetropia. They say that this is a good outcome of somebody with congenital esotropia. So somebody who's born with their eyes crossed, their brain doesn't really use their eyes together, you're trying to get it there. If you do stir business surgery and you get monofixation, you should say you have a good success. Yeah, these are bagelini lenses, Bob likes to use these but yeah, they can, you can interpret their crossed and uncrossed apopia, you can also get torsion that way, bless you. They're lined up, so one is at 135 degrees and one's at 45 degrees on the eye. Somebody, if you're looking together and they have orthotropia, they're straight, they should have a nice X. If they're suppressing their right eye, you're not gonna see that, you know, you're not gonna, oh, sorry, if they're suppressing their left eye, you're not gonna see this one going this way. So you're only gonna see this one. They have a little, I think this would be pretty hard for somebody to say, but it's missing in the middle. I don't usually use these lenses but you should know about them. If they have esotropia, you know, they have uncrossed apopia, right? So this right eye's gonna be shifted this way and then you're gonna see it as a V, whereas if they have exotropia, it's gonna be shifted this way because they have crossed apopia and then you're gonna see it as a V in theory. That's what this says. Yeah, and this is just explaining it. You can label the phobia and have a look at the after images. Oh, this is another similar test. It's kind of the same thing. I've never done this one, you know. But you kind of label the eye with a flash of light and then the same thing if it's, you know, if they have normal retinal correspondence, they're gonna see them together. If they have anomalous retinal correspondence, they're gonna see them as a T or a backwards T, prolific T. Sometimes on the oral boards, they like to ask weird questions like what is this device? I've never actually seen one of these, but it is called an ambioscope and it's somebody can sit in there and kind of dial in exactly what they have. So it would be a way of telling exactly how much in primary gaze, and it's pretty much just just primary gaze, how much isotropia they have, how much hypertropia they have and how much torsion they have. And then you can just read it out from a calibrated scale. So it's good for people who were binocular at one point and then for some reason were not because now they're getting double vision and try to figure out how to make them straight again. It can be really helpful for figuring out exactly how much torsion they have because sometimes that can be a little bit difficult to assess. You can use it for exercises to try to kind of get people to fuse a little bit better to overcome suppression and can increase their fusion amplitudes. I don't think anybody really does that though. It's just kind of an old school machine, but they do sometimes ask those weird questions on boards. What is this? Computer's frozen. This is what's called a land craster, a red-green test, where they, I prefer to use these. I prefer to use a double-mattox rod to tell what torsion is. You put two lenses over the eye, two double-mattox rods over each eye, shine a light with a Femhoff and then they should see two lines, one red, one, I usually do one red and one white, but you don't have to. And then you try to get them to move the little dials to, I usually make them parallel with the ground and parallel with each other. Sometimes they'll start fusing them and if you want to, you can throw a prism in there so that they can easily see that they are parallel to each other. Somebody who has different alignment in different fields of gaze, you can test their torsion. These are ways to measure torsion. You can measure with this, what we call the land-caster-red-green test, which is this test here where you wear these glasses and then the examiner shines a light and then the person shines their light and they try to, and they make them overlap with each other. So it can be useful for figuring out things like fourth nerve palsy or just any kind of incombinant strabismus where it's different in one field of gaze. Yeah, here's somebody with bilateral superior oblique palsy. You can see that they're not as, this is primary gaze, but when you go into down gaze, they start getting more torded and more esatropid. So after all that really fun stuff that you don't like to think about unless you do it all the time, strab was nice enough to put together some questions. Guess that's how you guys want to do these lectures now, which is great. We can go over these questions together. So which of the following essentially rules out the diagnosis of mono fixation syndrome? So we talked about mono fixation syndrome. It's just people who are trying to get some amount of anocularity when they have either anisomatropia or at like a small angle strabismus. So they are peripherally fusing because that is what, they have some kind of skatoma there, but they have peripheral fusion that they have bi-immaculate fusion. They do not have bi-immaculate fusion. So they do have peripheral fusion, yes. They do have absence of bi-immaculate fusion. Why is that? Because their foveas are not lined up. Their foveas are not lined up physically, and so they're trying to get some amount of anocularity with what they've got. So they do have that two lights seen on distance worth for that test. That just means they're suppressing. So yes, they do have that usually because they are suppressing most of the time. They have a little suppressant skatoma. They have peripheral fusion, and they suppress on worth four dot. Do they have 60 seconds of arc stereo? No, they don't. They don't usually know much stereo. They have about 200 or so. So they can see the fly. They might see the first or second or third circle, but they aren't gonna see much more than that. And that's what this all says. Oh, she said 59 minutes. Well, yeah. With the fly, yeah, you're just looking for gross spary octaves. Kids are not always great at these tests, but you'd be surprised. Some of them are pretty good. But the superior oblique insertion forms 51 degrees with the visual axis. What is the primane action of superior oblique? So why do we have a superior oblique, and why is it controlled by its own nerve? It's mostly to twist your eyes. So it works mostly if you tilt your head to the side. It will rotate your eye back the other way. So it's an evolutionary development. And I think it's more, they think like something to do with like fish or being buoyant and things. Your eyes kinda always wanna come up. So yeah, so if you tilt your head this way, you know, it's twisting, it's working most in this eye, so it's twisting your eye back to keep them that way. Which is why somebody with a superior oblique policy is gonna tilt this way. But if you tilt them this way, that eye's gonna go crazy up this way because it's not turning in and it's not pulling down to make them right. So you can just think of the superior oblique mostly as an intorter. It's, that's this mains function, which is why if you wipe it out, you look at somebody, if somebody comes in with a bilateral superior oblique policy, it can become, you know, it's usually after trauma and you'll look at them and they look dead on screen in all fields of gaze, but they tell you they're miserable. But then when you look at, like do a Lancaster Red Green, you'll see that they've got crazy torgene in down gaze. So they just can't fuse that torgene because that's the main purpose of the superior oblique. It's just to torque it. And it works more in down gaze. So the superior oblique works when you're, it pulls your eye down and in and twists it. So mostly twists, pulls your eye down and in. So what is the main action of it? It's an intorter. If it's in extreme adduction, I mean, that's where you look at the obliques is when your eye is looking at your nose. If it's going too high up, your inferior is working too hard. If it's going too far down, your superior is working too hard. So when you're looking this way, it pulls your eye down. And what does it do in abduction? It's still a torgor. So that's kind of what this says. So yeah, it's got that funny angle, but I think it's easiest just to think about the superior oblique. If you're looking to the side and your eyes going too far down, the superior is overacting. If it's looking too far up, it's overacting. So what is its role? It's mostly a torgor because that's why you get so bad with somebody who has a palsy of it. But it also pulls the eye down and you can see that if you look in and down. Thinking about it this way is like too confusing for me. I mean, I can't think about it that way, but I don't really. I think about it more like if I'm looking at somebody's versions and I'm looking around and I'm wondering what muscle's overacting. Yeah, I'm looking how the eye moves when it goes in towards the nose, if it's too far down. And you don't see superior oblique overaction very often, but you see inferior oblique overaction all the time, right? If you look this way and the eyes go with crazy up that way. I haven't looked at these. What are we on time? Are we close? Should we watch this straw or not? Yeah, I mean something to you. You guys can watch it on your own time. I just thought it was easier for me to visualize it with a video then. I guess we'll watch it and we'll see what it says. Because this is so exciting. Hi, understanding the actions of the extraocular muscles can be frustratingly confusing, so I hope this video helps. You may also want to watch a video on eye movement terminology for this. Which one? 158. The 23 degrees, the superior and inferior recti are aligned with the axis of the eye. They therefore act purely to elevate and depress the abducted eye. The superior oblique acts to be in taut and the inferior oblique acts to extort the abducted eye. When the eyes are ducted, the inferior oblique and superior oblique become the main elevators and depressors. The superior rectus now primarily in tauts and inferior rectus primarily extorts. How can you remember these eye movements? Well, I draw a simple diagram. This diagram shows the abducted eye due to lateral rectus, with elevation from superior rectus and depression from inferior rectus. It also shows adduction from medial rectus, with elevation from inferior oblique and depression from superior oblique. Finally, for the intorsional and extortion, simply turn the eyebrows into arrows. You don't have to remember all the lines up with this axis, this axis. I don't even remember them ever asking questions like that. I think it's just more important to just realize if they're lined up with their whatever angle, when they're in pure, whatever, it's always gonna be the same. It's not like it's an abductor in one gaze and an adductor in the other gaze. Yeah, the superior oblique is an intorter. It pulls the eye down. So the inferior oblique is an elevator is best seen in adduction. So we look at both of them in adduction. You are contemplating bilateral medial rectus recessions at a 45-year-old with long-standing ET during the course of your preoperative exam. You determine that he has anomalous retinal correspondence. What does that mean? It means that you measure 40 on their, with their ultimate prism cover test, but when you put up 40, they're depopic. If you put up something else and they're not depopic, yeah, then that means that they've got anomalous retinal correspondence. So which of the following may happen shortly after your surgery? Well, you're gonna operate for that what you got on the APCT. But after, they have, so you've corrected all their esotropia, you look at them and now they're straight, but they're telling you this, see double vision. So what kind of double are they gonna see if they were ET and now you've made them straight, but they're feeling like they're XT. Are they gonna have singular monocular vision? No. Are they gonna have monocular depopia? No. Are they gonna have uncrossed depopia? No. Well, if they're XT now, they're gonna have crossed depopia. XTs are crossed and ET's are uncrossed. So this is just saying, yeah, now if you've made them ET and they were ET and now you've made them what you think is straight, but their brain is wired to not be straight, if you've overdone them now, they're gonna be XT. So they're gonna have paradoxical depopia. I've only had this happen in one person and he was an albino and he was really XT. He, one of somebody else that operated on him before and he was really XT, he had like a 40 to 50 XT, so I fixed him. But then on alternate prism cover test, he was still XT, but he was depopic. But then I could never get rid of his depopia if I put up the prism and things, but after about, I think I said, well, I can put your eye back where it was. And he's like, yes. And the dad's like, no. But even when I put him back in is like four, he still couldn't fuse it. So he had some kind of altered the doctor, but it did go away eventually. He was, does that make sense? Cause I think I understand what crossed and uncross meant. Oh, it just means if you're like, it's what you could see with the worth four dots. So if you have, like, if you're seeing two lights with your red eye and three lights with your, and you're trying to figure out if, you know, with the fourth four dot or Maddox rods or whatever. So you're seeing these, you've seen two lights with the red eye, right eye, and you're seeing three with your left eye with the green. And if you're trying to figure out if they're crossed or they're uncross. So if they're exotropic, their eyes, and this tells you well, if you're, yeah, so if you're exotropic, your eyes turned outward. So your phobia is inward and light coming from straight ahead is falling on the temporal side, but you're gonna see it over here, which is why if you're XT, you're actually gonna see your images crossed. It's confusing. It's the same thing like everything's upside down on the temporal. And that's it!