 The other one that I use a lot is called the A-scan technique. And the A-scan is displaying, instead of displaying the picture at little bright dots, like pixelated pictures, it is actually vertical lines. And it's actually the same concept. I'm just looking at things in a different technology. And the A-scan is not widely used. Most people don't really learn A-scan. When they say A-scan, they think of biometry. When they measure the eye for axial length measurements for lens implants, they use an A-scan probe for that. But that is not the same thing that I use. This is called a diagnostic A-scan probe. This is a separate probe. It's not part of the B-scan. And it's very useful for many diagnostic approaches. But you can't use a biometry A-scan probe for what I'm doing. I can use this to measure the length of the eye. So this is more versatile. I can use this for more things. But most machines don't come with this. You have to buy it separately. And a lot of people don't know how to use it. But I found it very helpful to quantitate things. You can measure nerves with it, muscles, different things on the eye. And I'll demonstrate that. So we go on the machine. And this is going to show a bunch of vertical lines dancing around. So again, I'm in the same positions. I'm just putting the probe here in fairly. I'm aiming towards the posterior fundus. I'm going through the vitreous here. This is the superior fundus here. And I just scan it this way, going back and forth. And this has no mark on it. You might notice, like the B-scan probe, because there's not really a transducer inside going back and forth. It's just a sound beam coming out of this probe. So it doesn't really matter how you hold it. The orientation would not be affected by that. So as I aim towards the superior fundus, I look for any irregularities. I'm going through the vitreous. Here's the retina. Here's the orbit. I look for anything unusual there. And by experience, I know what I'm looking for. But beginners have a hard time with this concept. Now, a major advantage to the B-scan probe is examining the orbit. We can actually quantitate muscles, nerves. So if I, again, aim towards superiorly, if I aim towards the superior rectus muscle, I can actually capture the muscle right here. So this little dip in the pattern. So again, I'm going through the vitreous here. Here's the orbital area. And this is a muscle because muscles are more homogeneous than surrounding orbital tissue. The orbit's quite high-reflective because there's a lot of tissue inside to reflect sound. The vitreous doesn't have much. It's usually homogeneous. You get a flat vitreous, a flat line. And the A-scan shows the orbit has a lot of reflection. You have muscles, septa, fat. So reflectivity is quite high. But muscles tend to be more homogeneous than surrounding orbital tissue. So you get a little dip in the pattern. So it kind of dips down here. You see a little spike there, a little spike there. That's the muscle. I'm kind of doing a cross-section to the muscle. The muscle was here. The sound beam is going from one side of the muscle to the other. You can see the spike on both sides. I'll show the medial rectus muscle here. This is a bit more evident here. You can see these little... There's a spike right here and a spike there. So I'm going to measure across there. I use electronic calipers. I can get very exact measurements of the muscle thickness. This is quite helpful for any concern about muscle thickening diseases such as grave disease or myositis, infiltrative processes such as lymphoma, metastatic tumors. I can actually quantitate muscles. Whereas MRIs and CT scans, as good as they are, it's usually a qualitative judgment. People look at them and say, well, I think the muscle's enlarged. I don't think it is that I can be fine. If the muscle is quite large, that's very helpful. But if it's kind of borderline, it's really kind of a guess. But this can actually put a number on it. We have tables of muscle thickness. We can actually compare that to what I'm getting here and see if the muscle is thick and compared to the normal pattern for that individual. So that's the muscle. We do the same thing. I go around and measure all the rectus muscles. So that would be the medial rectus, inferior rectus muscle. It can be a little harder to get because of the brows in the way. If you angle the probe, kind of go back and forth with little movements with my hand, kind of angle the probe until I get some good spikes. Again, right here, this would be a muscle pattern. So through the vitreous here, back to the orbit. So there's a spike there, a spike there. So I measure from that point to that point. And that is the inferior rectus muscle. The lateral rectus, I put the probe nasally, aim towards the lateral rectus. Watch for that same spike pattern. So right there to there, I would measure that and quantitate that. And that's the four rectus muscles. I can then do the superior oblique by aim towards the trochlea. I watch for little spikes there. And again, the muscle here is further away from the globe. The rectus muscles attach at the globe and go back towards the apex. The superior oblique kind of curves around through the trochlea and attaches to the globe. So I'm kind of pointing right there where the trochlea attachment would be. And I can measure from there to there and quantitate that. Finally, the optic nerve. I can demonstrate that and quantitate it. So I usually go temporally, but sometimes the way the nerve kinks, it's hard to capture it. So I will try both nasally and temporally. But in this patient, it shows pretty well. So right here is my spike of the nerve. So from there to there, the nerve is close to the globe where it comes out of the back of the eye. So I can actually measure the nerve thickness from that point to that point. And again, to quantitate it, I just take my electronic caliper, put it on there, and that tells me the nerve thickness, which is normal. So that's just the way to quantitate things, which is very helpful, following patients with grave disease, muscle thickening diseases, optic nerve problems, increased pressure and intracranial pressure with pseudotermal cerebri, papillodema, optic nerve tumors. So all of these can be looked at with quantitation. And that is going through the eye. We also use techniques where we kind of bypass the eye, called periocular. So to look at the lacrimal gland, we can see it up here. I'm bypassing the globe. There's no globe pattern in there. And I can actually look at the lacrimal gland. This is a normal kind of lacrimal gland pattern. It kind of trails off towards the end. If it's thickened, if it's reflectivity changes, I can analyze with the A-scan. So that's just kind of a summary of the basic A and B-scan techniques. The B-scan does have an A-scan on it called a vector A-scan, which some people use. I don't find it very useful. It really is derived from an envelope from the B-scan. So it really... I don't find a lot of value to it. But here's an example. So here's the B-scan here. This would be the... This would be the B-scan here with the globe. And then there's an A-scan superimposed at the bottom. But that's not the same as the A-scan that I use. That's derived from the B-scan envelope. And it really isn't that helpful in diagnosing reflectivity changes, especially in tumors. We see a lot of melanomas, other eye tumors. So in those cases, I don't really use that. It's just sort of there. There's like a Staphyloma. If I want to measure an axial length, I can then use the vector to sort of find the Staphyloma and then measure for an axial length. But again, that's not really very often. So A-scan techniques...