 Something that we can't hear it's cute. So the definition of ultrasound is any takers frequency that's higher than the audible sound for humans. Okay. 20 megahertz. 20 kilohertz. Yeah. Yeah. It's sound reflection from tissue interfaces. Okay. So. Method. Frequency waves to produce images. Okay. How about generation of sound by electrical impulses? Okay. Well, technically the actual definition physically, which is sound is sound above the range of human hearing. And these are kind of ranges. We can hear up to 20,000 Hertz or 20 kilohertz. Dogs can do 40. Wells and dolphins can do 70. And bats 150. So. We're certainly on the low end of that spectrum. The animals can use this bats actually. Can often use it to locate insects. The tiny insects. To a night, you know, use their. Ellicution their generate sound. And they can actually capture insects. And so Mars have developed a defense mechanism. There's a breed of Mars. They can actually generate sound at the same frequency. So they kind of confuse the bats. They kind of send their signals out. So when they're flying around, the bats can't tell another bat from them off. So that's one defense mechanism they developed. So their frequencies used in ophthalmic ultrasound. Anybody know that. 20 Hertz. Eight, eight to 12 up to 50. Okay. Eight to 12. What mega Hertz mega Hertz. Yeah. Right. And so in medical ultrasound. Like the abdomen. They use lower frequencies. And why do you think that is why can. Why do we use such high ones and they use lower ones. They have to get more depth of tissue. Right. Yeah. So the higher their frequency, the less penetration. The higher the frequency of the sound is absorbed. It doesn't penetrate. As far as the higher the frequency. So. The eye, which is a small structure. And then. We can also have a lot of water. A lot of. Which generates sounds more easily. So. We've got these higher frequencies. And we use the probe that we usually use the B scan probe that you all use. Is 10 mega Hertz. And the a scam probe that I use the separate a scan diagnostic. It's eight mega Hertz. So that's kind of where kind of bread and butter standard ultrasound. We start getting into high frequency. They do have poster segment. They have a high frequency. Up to 20 mega Hertz. I don't have one of those. I've looked at them. And we'll probably get one at some point. They don't have a whole lot to what we're doing. There might be a bit better resolution. Kind of the virtual retinal interface. Or the macula. But with OCT, you know, being so powerful. It probably isn't. You know, if you're using OCT vitreous hair merger, whatever, then that would be helpful to have, you know, higher frequency for the poster segment. Now the answer segment, the immersion scans. I used about, about a 40 mega Hertz probe on my machine. But they go up to. I know Alan Crannell for a while was using. A 60 mega Hertz probe. And he was doing some. I guess. Trbeculotomy kind of work, threading tubes into the record mesh work. So. That's the high frequency. You really can't get much beyond beyond the. Oh, the cornea. The entire sclerosis. So you really can't even get into the entry chamber. Or behind it. So. You know, there's a lot of penetration. So that's, that's what we focus on. So the piezoelectric effect. Any thoughts on that? What that actually is. So it sounds like it's. The ability of certain materials to take an electric. Charger signal in risks. And in response to mechanical stress. And so the example. In this case would be the crystal that's used in the transducer of your, of the B scan probe. So it takes that. Electrical signal from the machine. Changes into the ultrasound waves then is able to detect the ultrasound waves and. Transduce it into that electrical signal. Okay. So I'm good Becca. Our bio engineer. So basically at the tip of the probe, there's a very thin, very thin crystal. And that is, as Mike said, it's generated electrical pulse stimulates that crystal to vibrate. And that vibration is what generates the ultrasound. And then the same crystal when this, this sounds generated, the sound away travels out. Hit something. And then it's reflected back. Into the probe. Of that same crystal. That is in. So there's like a pulse of a thousands of a second. And then that generates the signal. And then that crystal is dampened. Through internal. Electronic. Devices. And then that. The returning sound wave hits that same crystal. And again, vibrates it. And that vibration is picked up. There's electrical signal. And then. A display it on the oscilloscope. So the same crystal. Acting as both a sender and a receiver of sound. So that's called the piezoelectric effect. And this shows a, the upper left picture. There's a B scan probe. Opened up. So you take another, the membrane off and showing the internal. The actual transducer. That moves back and forth. So just goes back and forth in a horizontal plane like this. It doesn't rotate. It doesn't rotate. It doesn't rotate. It doesn't rotate. It doesn't rotate. It doesn't rotate. It's a plane like this. It doesn't rotate. It's just a side to side movement. So that's important to know. When we talk about pro position and things like that. That kind of clear. Bless you, Mark. Is that clear? I was wondering. So in the probe, is there one crystal or two crystals? same crystal that does both the transducing and receiving, or is it two, like one for each? Same crystal. It does both. The crystal is stimulated, electrical pulses, generates the sound, the beam, and then it is dampened. It'd still be vibrating if you didn't have somehow dampened, so it's still not vibrating from the poles, and then it will stop vibrating, returning sound hits it and stimulates it to vibrate again, and that's transformed into electrical energy, so mechanical, so mechanical pulse, you know, sound vibration is transformed into electrical. Okay, so it is the same. All right, so A scan versus B scan, what's the difference? I mean, obviously, they're different because they look different, but what really, what's the purpose of having an A scan? What does it do? How does it expand the B scan capability? The B scan is brightness, amplitude, and then A scan is time amplitude. Okay, that's right. What does that mean? So when you have the way the data is presented is that for B scan, you have the intensity of the waves are represented by brightness on pixels and coalescing, and then for A scan, you have the time between the media, or you have the differences between the media interfaces creating a linear, like a linear form of that representation. Okay, so basically back to your pixel idea. So on the B scan, each returning sound signal that is amplified electronically and displayed is a pixel. So a little bright dots that all form together, you know, the basic idea of how the television works, you're actually generating electrons and scanning those quickly over the screen to generate a picture, same with the computer screen, so the pixels all coalesce to form an image. So little tiny bright dots individually, and then the more you amplify that picture, the rainier it gets, you actually can start to see almost to the pixel level if you really amplify this picture, really in high magnification. And so on the A scan, what you're doing, you're taking that same little bright dot and instead of a bright dot display as on the picture, you're actually showing that as a vertical line. So each bright dot here is displayed on the A scan as a vertical line. So it's just sort of expanding that little dot, you just think about that little tiny dot that you take a pencil and put a dot on a piece of paper, and you just took that dot and stretched it into a line. That's what the A scan is doing. So each dot here on the B scan, here's in the orbit, of course in the glow, we don't see much because it's full of vitreous, but on the orbit, where all these bright dots are different interfaces. So you have, you know, septa, you have fat, you have muscles, nerves to generate interfaces from returning sound. Well, the A scan is just taking all those and making them vertical lines. Okay. And the advantage of that is, it's just easier to see. I mean, grayscale, which was the B scan is all these bright dots, they have different degrees of grayness. And on the A scan, actually, it's easier to see the difference between structures because of the vertical lines. And I'll talk a bit more about that with regarding, like intraocular lesions, like tumors, for that's important to know that. So there is some rationale to make, to have the A scan, it really does add information to diagnostic capability. Okay. So the concept of a vector A scan, anybody thought about that at all? What that means? Or do you know what that is? I wasn't super sure, but it seemed like that was, it was kind of the, it was like the perpendicular A scan almost that was taken from the B scan. But that's really the best, I couldn't find a great definition more than that. Okay. That's certainly part of it. And every B scan machine that I'm aware of does have a vector A scan. So if you push a button on the, on the console, on the machine that we have the LX machine, you take the B scan knob and you just hit it again, and that'll generate the A scan at the bottom. So a lot of companies that sell machines will, if you ask about, do you have an A scan, they'll say, yeah, we have an A scan, you know, it's here, push a button and show you the A scan at the bottom of the picture. So people buy those machines on the basis, they think they have an A scan. It really isn't. What they do is they, they take the B scan, and I don't understand all the physics of this, probably Becca does better than I do, but they can take the information from the B scan, and then, you know, treat that with algorithms and saying, and they can actually generate an A scan from that B scan information. So it really is, it's the same information, they're taking the same sound energy reflection back, and translating that into a A scan. And the problem is it's just really, it's the same as the B scan, basically it doesn't really add information. It shows it a bit differently as far as the display, as far as the diagnostic capability, it really isn't the same. I trained with Dr. Carl Ossona who developed the A scan. He actually was from Austria originally and came to Iowa and then ended up staying there. I spent a year with him, and the A scan that he developed is a freestanding A scan, is different than the B scan, and it's the amplification of it is called an S-shaped curve where instead of being logarithmic, he's able to generate this curve to process information where you kind of capture the information in the middle of the curve, which really optimizes it. So the concept is all kind of built into that A scan, but it's a separate diagnostic A scan. It really isn't part of the B scan that we are used to. So this shows the standard kind of a B scan, and all the B scans have a mark on them somewhere. The elix machine has this little thing, but sometimes it's just a line or a dot, but the purpose of that is to tell us which way the transducer is moving. So again, it's not rotating, it's moving in either a horizontal or vertical plane. So here is where the mark is, and the transducer inside is going back and forth, and here in this picture it would be top of the picture to the bottom of the picture. So in a vertical direction, if you rotate the probe horizontally, then it's going to be going in a horizontal plane. So here's in a vertical plane, if you move it in a vertical, in a horizontal plane. So that mark is important to tell you which direction the transducer is moving. The A scan doesn't have a mark on it, and the reason is because there's not a transducer inside going back and forth, it's just generating an age pole that generates a sound wave that just goes out, but it doesn't rotate back and forth, and it doesn't move back and forth like the B scan. So the B scan is actually moving back and forth, generating the sound waves as it moves, whereas the A scan is a stationary probe, just generating sound waves. So it's a lot thinner, doesn't have to be bigger because of the, you don't have to have the transducer going back and forth within it. But again, the tip of this probe has a thin membrane I could talk about before, the same as the B scan, and the P's electric effect, whereas the thin membrane is generated, simulated by electronic pulses, generating sound waves, and they hit the probe and form a picture. So it's the same concept as that P's electric effect. All right, this is a vector A scan. This shows the B scan picture up here, and at the bottom, you can see an A scan. So it does generate an A scan picture, and the only really use I have for this is if I have like a staphyloma. So here's a case. So here's the cornea up here. Here's the iris going through vitreous, and here's the staphyloma. See, I kind of bulges out in the back. So if you're trying to do an axial length for a biometry, sometimes you can be deceived, like when you have the patient focus on the light or whatever, and the sound wave hits the back of the eye. If you have a staphyloma, you can be deceived. If you hit on the edge of the staphyloma, you'll get one axial length. If you hit in the depth of it, you get another axial length. So which one do you use? That can be a real problem. And even the IL master has the same issue that if it's a staphyloma, are you hitting the bottom of the staphyloma? Is that the true axial length? Are you hitting on the edge of it? And that can really determine the power when you finally get your axial length to plug into your formula for your lens implant power. That'll obviously be different where you are in the staphyloma. So the vector A skin, you can actually move this line here, this dark line. You can move that with a dial up or down. So you can put the vector here. You can put the vector here, the vector here. So the beast can actually let you visualize where that beam is going, where it's hitting. So if you want to be in the bottom of the staphyloma, you can, you put it in there. If you want to be on the edge, you can put it up there. So the question is where is the macula? We had an interesting case a couple of years ago where there was a staphyloma right to the edge of the macula. So the question was, was the depth of that in the macula or was it just to the side of it? So in that case, I used an OCT. So I took the OCT and we could tell the staphyloma just entered just right the edge of the macula. So we didn't want to be in the depth of the staphyloma because that would be too long. So we actually used the vector on the ultrasound machine to move it slightly to the side of the staphyloma and got the actual length. So then the power ended up being correct when we patient, but after a surgery was refracted and it was like real close to planar. So that's an advantage of that's the one time that I use that vector A scan and those situations. Is that going to make sense? Yeah, it does. In any way. So the A scan on this, you can look at it, you can say, well, if you had a tumor, you might see this is the surface of it and maybe internally, it's highly reflective. You can sort of get a rough idea. So if you had nothing else, you could still use this A scan to sort of help. But the real diagnostic criteria that was established by Dr. Sonig, really, it doesn't work very well. So if a person has a chance, has a choice, they have the budget to do it. I always advise them to get a free standing A scan. So like we have in all our machines that we use, we have the separate B scan probe, A scan probe. I think they all have the biometry. I mean, they have the high frequency B probe too. Okay. So perpendicularity, which is really important being perpendicular. How do you know if you're perpendicular to a surface? If you're doing an ultrasound on a patient, you want to be perpendicular, trying to get the surface of a lesion or the u in biometry, you want to get the, you know, get on the retina. How do you know if you're perpendicular to a surface? That's the highest amplitudes. Yeah. Uh-huh. You want to, you know, maximize the height. That's right. This demonstrates that. This shows, you know, if you're perpendicular to a surface, you get maximal returning energy. So the sound wave send out, gets the surface, bounces back, you get a high spike. If you angle that probe, obliquely, you lose some of the energy. You know, some of the sound energy goes off to the side. It's not reflected directly back, just like light. You know, if you're reflecting light from something, if you're perpendicular, you get maximal reflection. And if you're oblique, you get less. So and more oblique, you are the less energy you get. So being perpendicular, you can actually look at the screen and see on the B scan, you go by brightness, the brighter the image more perpendicular you are. And the A scan, the higher reflective and the steeper it is, the more even, you know, if it's on the A scan here, I'm comparing, this is the initial signal from the probe. Every probe generates a certain signal. And this is it from the A scan. And you want to compare that to the height of the surface you're looking at. So going through the eye here, here's a small tumor. And as you hit the tumor, you get this high spike going up. And I know here I'm perpendicular because this is maximally high. If I compare this to the surface, to the initial signal, I get a very high spike here. It's even and smooth. There's no little nodes on it. It's just an even surface that is a maximal perpendicularity. And the advantage of that is I then can then analyze internal structure. I can look inside this. This is kind of a low reflective, slightly irregular. There's a little spike inside. But I really can adequately analyze internal structure, which is really critical for intraocular tumors. The criteria for melanoma diagnosis really depends on that internal reflectivity. If it's regular, if it's high or low, if it's even. So I'm perpendicular here. And this is the same lesion where I'm oblique. This is just an artifact from being oblique. But here's the actual lesion where the arrows are. And that shows that I'm not perpendicular because this initial signal isn't very high. It only goes to that height compared to that height. And if I look internally, if I compared internal signals to the surface of this, they're much higher. Just forget the rest of it. Just look at that part. Compared to the surface of this lesion, internal reflectivity would actually be high, medium to high, whereas here's low. So I've changed my diagnostic criteria by being not perpendicular. So that's why it's important to do that. And again, it's biometry, if you're measuring the actual length with ultrasound, you need to get that retina spike really high, steep, even. So that's the importance of being perpendicular. The average sound velocity in vitreous? 1500 meters per second. Yeah, that's about 1532. And why is that important? Well, if you're ever doing your own formulas, we actually, I first started doing ultrasound, we didn't have all the formulas we have now. So we actually had to kind of do our own. So we actually had to do the calculations and plug in numbers. So we actually had to know those numbers. So it's just right now, you don't really need that with modern instrumentation, at least to know the basis of it. So the denser structure is the faster the velocity. So water is the lowest here, and bonus the highest. So aqueous vitreous is kind of in the middle. And the lens you can see is higher, the lens is denser. So you get faster sound velocity through the lens. And some formulas, I don't think they do now, they just require actually entering the different numbers. You'd actually enter a number in for the anterior chamber, which is, you know, aqueous. And then you'd enter a separate number in for the lens, which is a different number. So then the calculation of formula was sort of average those and use that as part of your calculation. And I'd say now this is more of an average, I think most formulas, most things that we do use just this number as an average with really disregarding the lens. But there's a slight tiny error introduced by not using a separate sound velocity for the lens. That's why it's important to kind of know that concept of different sound velocities. All right, acoustic impedance, anybody want to tackle that one? I'll even give you the formula. So it's defined as sound velocity times density. It's like the resistance that sound faces when going through a like substance. Okay. Yeah, so it's how difficult it is for sound waves to get through something that has to pass through. Okay. Right. And so the importance of this basically is probably less the actual equation, it's just more is a difference concept. So when you go through any kind of a tissue or structure, you have a certain acoustic impedance number, you have a value based on this formula, the sound velocity times the density of that given structure. When you enter another structure or encounter it, you then are changing impedance. So if you go from like vitreous to like a tumor. So here's an example kind of walk you through this. So here's a densely cellular structure. This is a melanoma. They have a lot of cells all kind of packed together by homogeneous. You got a few blood vessels kind of scattered around, but basically it's a fairly homogeneous tissue. So this homogeneity really the sound doesn't have a whole lot to reflect back from. So if you go into the vitreous on the B scan, you get darkness. And then on the A scan, you get low reflectivity. All right. So you're going through, oops, there we go. You're going through the vitreous here. So here's the initial signal from the probe going through the vitreous. There's a little noise right there. That's just against artifact probably just from not being quite perpendicular or whatever. Because the vitreous is usually very, very flat. There's no interfaces corresponding to darkness on the B scan. You then hit the surface of the tumor. So here it is. Here's a small melanoma. And so you hit it. The surface right there. Here's the surface on the A scan. So that change in impedance, you're going along here to certain sound velocity of certain density, aqueous, vitreous density. And then you hit this tumor, which is a different density. So you change your sound velocity and tissue density. So that change generates that spike. And the same on the B scan. So you're going from one impedance value to a different one. And that change, that interface between the two gives you that surface. So the B scan, you see it here. A scan, you see it here is that spike. Once you're inside, you're at a different impedance. Again, because you're inside this tissue, which melanoma has different impedance than other tissues would. So that difference has a fairly homogeneous structure. So again, impedance starts to drop. It becomes lower. Almost not quite as low as vitreous, but slightly above vitreous. This is a very dense melanoma in the situation. And the B scan shows, again, the brightness corresponds to density. So you can see the problem here with the B scan. This looks pretty bright. So based on the gray scale, that could be a melanoma. That could be hemangioma, could be metastatic. It really doesn't. The shape is very, very well defined. That's the use of the B scan. But once you're inside that lesion, really to determine tissue differentiation, it really is hard because you just have kind of a gray scale. And the human eye really has not the ability to really define gray scale that well. Whereas the A scan, you can see very obviously, it's a little reflective, it's very irregular. So here's the advantage of the A scan where you've taken those pixels and instead of being a gray scale display, you've gone to a linear vertical display. And that just allows us with our minds and our eyes to be able to sort of see the difference more obviously. So this is a good example of that. So this is impedance here showing you're going from a vitreous to the tumor, get a high spike. Once you're inside, you start to get more homogeneous, you get lower reflectivity, then you hit the retina. So you change impedance again, another high spike at the retina. And once you're in the orbit, you get a lot of interfaces. So there's not much chance for the sound to start dropping down again to baseline. These interfaces keeps the sound beam keeps hitting interfaces and bouncing back. And so you get all these different interfaces inside the orbit. So that's a good demonstration of the difference here. And this is the impedance concept where you're changing going from one tissue to a different one, getting a change in p. So here's from one tissue here, the vitreous tumor orbit. So you can see the difference in display in each one. And the B scan shows the same concept, but it just, it doesn't internally, once you're inside that structure, the differentiation is much harder with the B scan than the A scan. Is that sort of clear? That's probably the fundamental concept of ultrasound. If you understand that, you really kind of know what you're doing when you're looking at different structures. So any questions about that? Okay, the B scan probe. Now this is an example here. This is the orbit. This really illustrates that even better. So these are different orbital lesions. And this is the first, and here's normal. So you're going through the eye here. So this is flat vitreous. Once you're in the orbit, you get all these high spikes in the orbit from all these different interfaces. So you get, you know, muscle, septa, fat, whatever is in the orbit. So you get a lot of interfaces normally. Here's a lesion. And this shows going through the vitreous. And here's the lesion, which you can see right away is different than the normal orbit that is wider. And these, these spikes are kind of going up and down. It's where you go down pretty low, up pretty high, down pretty low, kind of this seesaw up and down variation. This is a cavernous man's yoma. And that corresponds to the A scan because the sound beam starts to go through one of these little honeycomb cells full of blood. And it starts to go down because blood is homogeneous. You start to get a dip in the signal. You get an interface changing impedance. You get a high spike. You hit, it goes up, hit another cell of blood, starts to go down, its septa goes up. So this up and down, back and forth, seesaw kind of picture corresponds pathologically to the tissue. That's what first really excited me about A scan. I did my, I did my residency at UCLA. I used to spend time around the ultrasound department and I just really was fascinated by this concept, being able to actually differentiate things pathologically. Another lesion here. And this is actually a benign mix cell of the lacrimal gland. So this is going, this kind of up and down pattern because pathologically that's what you have in a benign mix cell. You have these areas, cystic areas of tissue, and then you have tumor beam around that. So the up and down pattern. And this, it looks like a hand yoma a little bit. It's a bit lower as you go into the lesion. It's kind of energy is absorbed and it starts to drop off. And also where the look lesions located, most human gnomes are kind of in the intraconal space, red lacrimal gland tumors are up in the superior temporal area. So again, by location, you sort of differentiate them. But even with that, you can see some difference between these two. This is a meningioma. You can see again, the density of tissue with some interfaces. This is a lymphoma with real low reflectivity, very dense tissue. So it's less important to know what these all mean. This point is just to see the difference. You can just see how the a scam really just takes that information and makes it more interpretable. You can see all of the spikes. If you had grayscale with a B scan, this kind of all mudges together. When I first started doing ultrasound, I bought a book by Jackson Coleman about B scan of the orbit. Now I kind of looked the same. I didn't, he had all these chapters on these different lesions and he would talk about differences, but it was just so subtle. It's almost like the days when I was before MRIs and CT scans again, I trained in those days of just plain film x-rays. These guys were amazing. The radiologists, we'd have conferences, they'd show these pictures of x-rays of different things in the orbit, and they could tell often by inferring, by changes in the bone, what lesions were, but really to redefine lesions, obviously with MRI and CT, we far surpassed that, but that art of being able to take a plain film x-ray, make all these little nuances and inferences about subtle changes. The same with the B scan. The B scan really, by itself, is really hard to tell a difference, but the A scan just kind of amplifies that difference, and that's why it's important it can be a real addendum to other modalities. All right, so on the examination techniques, we have the basic views, which are axial, putting the pro directly on the cornea, going straight back, or transverse or longitudinal, and I, all of you, I think as you've worked with me, I've kind of, I always ask you about this, which pro position is. So how do we define a transverse position? Any takers on that? It's when the transducer is moving parallel to the limbis. All right, there's my man. You can graduate now, Mike. You can, you can, you passed, so yes. Exactly right. So when the transducer is moving parallel to the limbis, so here's a limbis here, and again, this is just a two-dimensional picture, so you have to think three-dimensionally, but that transducer is moving back and forth, it's moving towards, out of the plane of the picture, and then back into the depths of the picture in a parallel position to the limbis, and see the beam here is generated, again, that's parallel to that limbis. If you rotate the probe where the mark is perpendicular, the transducer is going now in a vertical, up and down direction, and that is perpendicular. So define, transverse is defined as parallel to the limbis from the transducer moving that way, and the marker tells you which way it's moving because that's the transducer inside is moving back and forth, and then the longitudinal, when it's vertical, when it's perpendicular to that limbis. So those are two positions. Why is that important? Because you're doing different, especially with tumor measurements, which we do a lot of, a lot of melanomas, and a lot of those are treated with plaques. They didn't know how to make plaques, the radioactive iodine plaques. Actually, once we do the measurements of the tumor, and they're going to treat it, they will then send this to the, to the radiation people. They'll actually fabricate the plaque based on those measurements. So they need to know these different dimensions. The tumor is quite round, quite symmetrical. They're pretty much the same transverse and longitudinal measurements, but if it's kind of, you know, elliptical, not symmetrical, then you have different measurements. And that's important to really cover the whole tumor with the plaque. You want to always overlap a millimeter or so. You're making these plaques to be sure you kill all the tumors. So these are not just theoretical concepts. They really are practical to know what you're doing. If you can do an axial view, you can put the probe right over the cornea, in which way the marker goes or doesn't really matter because you're just going straight back. But the disadvantage of that is that a lot of times patients don't like that on their eye. They kind of get nervous that you're coming right down in the cornea. And also you have the lens absorbing energy. So you're losing some energy. So you don't get quite the resolution that you would with when you're bypassing the lens with an oblique position like transverse or longitudinal. So those are basic pro-positions. Dr. Harry, this might be a dumb question, but March and I were talking yesterday about what's truly transverse and longitudinal. Because I guess when you say perpendicular to the lumbus, I get confused because the lumbus is round. So can you kind of just clarify I guess pro-positioning in that sense? Okay. Way to get back to your Euclidean geometry class. All right. So even though it's round, even though your lumbus is round, if you take a line and you kind of drew the line, you can either draw the line along this way, along the edge of the lumbus, or you draw the line that way bisecting the lumbus. Or bisecting the lumbus. So here you're going parallel. That sound beam is actually going back and forth parallel. Just think of the sound that's transducer is moving back and forth like that. If you move the transducer here, it's going like this. So you're bisecting that lumbus. So that is perpendicular to it. Does that kind of make more sense? Yes. I guess because even with longitudinal B-scan, you would be parallel to the inferior lumbus. Do you know what I mean? But I guess your reference point is changing your reference point, I guess, is what you're, I understand now. The probe is always touching the edge of the lumbus, so you're always at the edge of it. But the way you think of the sound beam, the sound beam that's generated, is going, in this case, it's going in a, it's not parallel. It's actually going this way bisecting. Does that make sense? Yes. I was also confused because it seemed like when I was, it seemed like people describe like lots of many different transverse views. And obviously you can do that with the longitudinal view also. But it seemed like people mostly just did like the longitudinal macular view. So I was a little confused as to do people do the longitudinal view, like 360 around, or do they kind of do transverse 360 and longitudinal just for the macular or something, for the l-mac view? Good question. When I do it, and technically you should do both. You should go in six different because each B-scan sound generation is 50 degrees, 60 degrees. So 60 degrees are the fundus you're covering. So six into 360 is 60. So if you take six views, you could cover the entire globe. If you move the probe around, you start in fairly in game. You go, maybe you put the probe at the bottom of the eye here and you're going towards 12 o'clock. You move it over to four o'clock, over to two o'clock. So you go around in six different clock hours. You're covering the entire extent of the fundus. And so technically you should do a transverse view to do all that than longitudinal. The advantage of longitudinal is you can get a little further out. The sound beam when you're doing this allows you to get a little bit more towards the aura, whereas a transverse is harder to do that, just kind of technically, ergonomically. So you should really kind of do both. I'm lazy and I just usually just do one. I'll just do transverse, go around, you know, just scan it that way. But I try to really angle the probe as far as I can. But if you watch me, like if I get a vitreous detachment, I'm looking for a retinal tear, you know, it's got an eye full of blood. You can't see the fundus with the ophthalmoscope. So the ultrasound is really important to try to localize the tear. So I will use this position to really get as far as I can to really look towards the aura with the longitudinal position. I'll go around and try to do the different positions. So you really should be doing both. But yeah, I've done this enough. I just kind of know what I'm looking for. And I take shortcuts. So I just usually use the transverse just because it's faster. That's a good question. Okay. So three major, we talked about the three major propositions, actual transfer of longitudinal, uh, emergent ultrasounds. Why do we have to do all, you know, put this thing between the highlights and fill it full of water? Because we have to find like the focal zone of the image and only the middle third of an image is in the focal zone where is the first third is blurry and the last third is blurry as well. Not a focus. Okay. That's good. So when you put the probe against the eye, if you put it directly on the eye, let's say the, you know, the slurs out here, I put the probe directly against it. This is called the dead zone. And this area here, based on the mechanics of the probe, the physics of it, the way that when the sand is generated by the crystal and bounces back, this area here, you kind of lose information. Somehow buried in here is a sclera. And let's say you're doing an axial position or you're, the lens is in here somewhere, enter chamber. We really can't see any of that because it's all buried in this dead zone. So you really, if you're trying to look at it, enter a segment tumor or something, you wouldn't be able to see it because of this dead zone. And the A-scan, the same concept there, try to find an A-scan here to show you. So the A-scan up here, this is the desert of the A-scan. So this area here is about three to five millimeters. And within that, it's buried all whatever you're touching. So if the probe is right against the sclera, you're going to have a sclera in here somewhere. If you're, the axial view, you're going to get the lens in here, enter chamber. So you just can't see that. You really can't differentiate it. So that's where the immersion concept comes in. This is an immersion scan. So here, this is just a regular 10 megahertz B-scan. You can do immersion with that. You don't have to always have the high frequency scan. But you got a little sclera shell here to put the probe in. I'll show you a picture of that. And then the cornea is here. And here's the iris. And here's a tumor. You can see a solar body tumor that you wouldn't be able to see. You wouldn't miss that if you just did a regular contact B-scan. If you put it right against the eye, that area is in the dead zone. But here, by moving the probe back in that immersion bath of water at the cellulose, you can actually see that structure. So it just moves that probe back and lets you look at an area that otherwise is hidden. So that's why immersion is important, because you can see structures. So again, here's an XO view. Here's the cornea. Here's the enter chamber. Here's the iris. Here's that part of the tumor. All of those would be hidden if you didn't do the immersion scan. And I forgot to put this picture in this series. But when I trained again, there was, we used to do, we had a big frame, big metal frame set up. We put a big plastic drape within that frame and then fill it full of water. And the poor patients, under all this, it's like they're being water-bordered. They didn't like it. They were, you know, if you're claustrophobic, you just, it was miserable. So all these techniques we do now with these clerical shells and things really make that easy. And I think Tina was asking me about, you know, immersion. I guess through doing cornea work and things like the anterior segment, if you don't have a high-frequency probe like we do here, you can still use a 10 MHz B-scan probe. You just take a tonal pin cover or cut a tip of a glove, exam glove off, put that over the tip, fill it full of fluid. You can use that. This is what was done in this case. This is just a tonal pin immersion scan. We just didn't even use a square old shell. We just put this tonal pin cover over the probe, fill it full of saline solution, and then we can actually see anterior segment structures. You don't get the resolution you do with like a high-frequency UBM probe, but you can still see it. You know, you can still see there's a tumor there. So that's advantage. So silicon oil, how does that affect the ultrasound picture? Dr. Herr, you could, sorry, just, can I ask a question about immersion scans really quick? I also read that it's really important to, or like it's the gold standard to do immersion scans when measuring for axial length of biometry, just because there's no indentation of the cornea to affect the axial length. But I just wondered your thoughts on that. How much does that, or could that really affect your measurement? That's a good question. And obviously, you couldn't even see the cornea if you didn't do some kind of immersion. So a lot of the, before IOL master became popular, a lot of the A-scan units were for biometry, the probe had a little build-in water bath. It wasn't just this crystal white at the tip of the probe like we have now. There's a little build-in water bath right inside, and that gave you enough immersion to be able to stand the probe back and actually identify the cornea and the anterior segment structure. So, and again, indentation, that's the one problem with that concept though. As you say, if you did that with that probe right against the cornea, touching it, you could get a small amount of indentation, and that could affect your measurements. I mean, your final calculation. So, let me show you this slide real quick, I'll just kind of skip over. So this shows, if you have a millimeter air and axial length, that translates to a 2.5 diapter air in your IOL, which is pretty significant. So that shows how some cord really gets us down as low as you can. So if you take a tenth of that, even a tenth of a millimeter air, you're still getting a 0.25 diapter, which is probably within the range of acceptability. Now, Dave was modern refractive cataract surgery. Patients are demanding a lot more, and they want to really, we've seen this, patients at the VA, we have a patient that was kind of under corrected, and he's kind of constantly unhappy. We have to kind of massage him every time he comes in, making him happy. Sure, that was my patient. I think last time, I think he was actually pretty happy. Last time I saw him, though, I think actually he was finally accepting it. He's about, I think, a spherical equivalence about like a minus one or something close to that. And he's really without glasses most of the time now. He wears them to drive a knife, so he really finally kind of accepted it. I thought he would. I think we just kind of, you know, gave him the chance to kind of get used to it. So but anyway, it just shows the sensitivity of this. And K readings too, they're not quite as, it's almost like a one-to-one here, like almost a one-diapter air in your carotometry translates to a one-diapter in your IOL, but the actual length is really a pretty sensitive formula. So that really is important to try to minimize error. And again, if you push the probe against the cornea and compress it, you could give us, you know, theoretically shorter eye than really is true. So that's the importance of not trying to compress the cornea. So that's why most immersion techniques use a little kind of shell or something to actually separate the probe from the cornea and not push on it. So silicone oil, you can tell right away if a silicone just by, you look at this picture and the eye just looks funny. It's kind of, the retina is kind of hard to see. And this is bigger. So this is an eye with silicone in it. This is after silicone has been taken out. So this is the same eye. It shows the difference. You can just see the eye is not as long. So silicone gives you an artificially long eye. And the reason for that is it slows down the sound on slower. So these are all the lost sound velocities. So remember the average sound velocity in vitreous is what you remember that number 1532. So that was that's a normal vitreous. And this is with silicone oil. And if you're fake or a fake, it changes because of the lens velocity, but sound velocity and lens, but it shows us around 1000 compared to 1532. So that's quite a difference. So that's slower. And so the machine interprets that since it's slower, it takes longer for the sound to get to the retina back again. The machine thinks that's a longer eye because if it takes longer to get back to the to the to the probe, the eye must be longer. Even though even though it's not, it's just actually slower sound velocity. So silicone oil, I'll give you an artificially artificially long eye. So most of these are like around 30 to 35 millimeters. If you use that for your IOL, you'd be way off as far as your calculations. So you have to really correct for that. And again, I first started doing this, we actually had to go back and use a formula, we would take this number over 1532 times that by what we got on the ultrasound and get a number for the actual length. And now it just does it automatically. I'll master just goes right through this does a immediate correction factor for it. The ultrasound machine, we actually have to change the gain, the setting on the machine to actually show different sound velocity, which is easy to do with the machine that we have, but it still shows how that can affect that number. Okay, so silicone oil, if you see a big honey looking eye, that usually is going to be an eye full of silicone, you know, kind of right away that is a silicone oil in that eye. Okay, this shows that concept of immersion. So this little shells between the eyelids, you're putting the probe inside that full of fluid saline solution or something, that allows you to separate these different structures out. So here's the tip of the probe, you get the initial signal we talked about before, you go through the little shell here, there's that space here, you hit the cornea, you get that signal, you go through the answer chamber, that's that space, enter lens there, through the lens, post your lens, vitreous retina. So just separates these structures out. And this probe is right against the cornea, you would lose all that you would just see kind of this spike here, maybe just the edge of that, but you wouldn't see any of that. So you really couldn't even do this immersion scan, you really could separate out the structures unless you did an immersion scan. So it just shows the importance of somehow backing this probe away from this front of the eye. And we used to have these, because when I believe it or not, when I first trained, we didn't even do axial length, we didn't do ultrasound biometry, we just put a standard lens implant, everybody got a, I think a 19 diopter lens implant, we just kind of took the average, you know, person's refraction. And that's what they would all get, which works a lot of the time. But if you have, you know, if you're myopic, hyperopic, have a long eye short eye, you get these terrible surprises up to nine diopter surprises. So they refer to common in those days. So we've come a long way. And again, that concept about sensitivity about error. All right. So all that we've learned all this theory and stuff we've been talking about, let's translate that into something kind of practical here. So tell me, looking at this, let's do a, here's a B scan of a lesion. So here's a lesion here. Going through the vitreous. Here's the A scan. So what is the A scan look like that? Yeah. So what's your diagnosis of the A scan of the lesion based on the A scan characteristics? We've kind of given you a hint here. I've shown you the lesion. I've shown you the pathology. But just if you have the A scan only, how would you describe that A scan? So you're going through the vitreous here. Here's the surface of lesion. Here's the sclera. So reflectivity. Hi, reflectivity. So hi. Is it for your regular? Is it irregular? It's irregular. I mean, it's up and down, but it's in a regular pattern. It's not like really crazy. Like you go way, way down, way, way up. It's all kind of in the same level. So like instantly, I know that's the hemangioma. It's just, I look at that like in three seconds. And I'd probably go once a month, I'll get a patient referred from a good retina guy in the community. And they'll say it's a melanoma and they told the patient that and they're all set to be treated for that. I'll look, I'm right away. It's not a melanoma. I just, I can just say like 99.9%. That's not melanoma. It is all look like that. Whereas a B scan, that could be melanoma. You know, that's just kind of not specific. That gray skill could be, you know, the differential of, which we'll talk about a bit tomorrow, intraocular tumors, that could be any of those. So the ACE scan right away, you just, wow, you just know what it is, you know? So that's just, that's just a value of the ACE scan. It really just takes all those little pictal areas of gray skill and puts them in a linear fashion that we can actually see and recognize more easily. I have a, so I have a question about this one. So in the pathos, you see that, but I guess to me, in the B scan, I would think that it'd be more sawtooth, I guess maybe more irregular than you, like the previous ACE scan that you showed us since there are all these different septae and blood vessels. So that's why they're like, confuses me that it's, it's so homogenous, I guess. Right. And again, you think about the structure pathologically. Now this is really, this is microscopic. These are really little tiny spaces. So if you're a sound, if you think yourself as a sound beam, you're going through this little vascular space full of blood. Blood's pretty homogeneous. You start to get a little drop in the, in the spike. Homogenious, the structure is the low reflectivity of those less interfaces to reflect sounds. So vitrious is very flat. So you start to get a little drop in the, because of this, the blood in the space, but then you hit an interface pretty soon. You know, it's really just a microsecond that you're going through this little tiny space. You hit an interface and it goes up again. You go through another space, starts to go down, and it goes up again. So there's not really time for it to go down very far, because these are so small. These are big, huge spaces like a cavernous manjula in the orbit, then you do get more of it, you know, really going down, really up, really down, really up. But here there's so little, there's not really time for it to go down very far. So you kind of stay on the high side, you get little handy up and down dips, but mostly as high. Does that kind of answer your question? So if these were bigger spaces, you'd get a lower dip, because these spaces are full of blood, blood's homogeneous. So you start to get the sound going down because it's homogeneous. But because there's so little, there's not time for it to get down very far. Here's another space and it goes up again. So you get really, it's generally quite on the high side. Orbitally manjula, which is bigger, it's just bigger tissues and bigger spaces, then there's more time for the sound to go down. So you get more of this up and down, see some in the future. Does that kind of make sense? Yeah, that makes sense. Okay. All right, bonus question. Is Cole on this, this morning? Come on, Dr. Harry. It's not Cole, my man. What is it Cole? Go for it. Oh man, let's see. So you take half of the astigmatic power, so a quarter and then add to the spherical covalence. So minus two then. Is he right? Everybody agree? Yeah. All right. Now why is that important? Why do you care about spherical covalence? Will it ever matter? Can you see a context or that would matter to know that? If you're putting in a non-toric lens and a patient with a stigmatism? Yeah, that's true. A non-toric contact lens as well. Yeah, like a hard contact lens? Exactly right. Now soft contacts often are toric and you want to have astigmatic and we're so used to now that with, you know, we think of a stigmatism, we're putting toric lenses in. What's the cutoff at the VA? Is it like one diopter or you start thinking toric lenses? It depends on different attendings, but usually a little, you know, anywhere from .75 to one, then we at least run the calcs and see what we have. They only, I mean, we only go down to T3, so. Okay. But before toric lenses, you know, as you said that we didn't really have that, so you just had to sort of, you had to get this close as you could to what, you know, you thought the power was going to be kind of, you know, the astigmatism is still there and you're still going to have a little error because of that. But if you can use this, you can get kind of close to it. And I use it. I check kids at the detention center, I volunteer and take glasses out through them. And instead of, I actually take glasses with me. I used to try to get the glasses made for the kids, but the time they, you know, I sent them to the optician, got them made, brought them back. The kids were gone, such a high turnover. I just take a bunch of glasses with me. I got all these spherical powers, up to minus one, minus 10 or so, and half die after steps. I just give them glasses on the spot. And astigmatism, you know, usually I just use this. I just, I have up to maybe three dodgers of astigmatism. I'll get spherical equivalents. And they're actually pretty close, you know, for kids that don't have glasses and can't see, that makes a big difference. If they get real high numbers, I will have glasses made and try to just trace the kids down later. But in a practical sense, that is important to know that, how to make that calculation. And so anyway, call you got it. So you can come back to the VA now. All right. So that's it for ultrasound. Any other questions or we're good?