Today, with improved techniques and surgical technology, cataract surgery outcomes and patient expectations have greatly increased. It is therefore important that surgeons be able to give a superlative intraoperative performance time after time, even in challenging ocular environments, such as small pupils, floppy irides, dense cataracts, zonular weakness, vitrectomised eyes and high myopic eyes. The discussion will include what technique modifications should be made, and how the fluidics parameters as well as ultrasound energy should be used to their best, so that surgeons can ensure clear corneas, quiet eyes, and bespoke surgical outcomes predictably and reproducibly in every situation. It will be useful to both, beginner surgeons, as well as experienced surgeons.
Lecturers: Dr. Abhay R. Vasavada and Dr. Shail Vasavada, Raghudeep Eye Hospital, India
DR A VASAVADA: Well, welcome to this webinar. We all here at Raghudeep Eye Hospital, Ahmedabad, India, are very excited to interact with all of you across the globe. We do have a financial disclosure, that we received recent grant support from Alcon Laboratories, and on this very fascinating topic of: How do we optimize our risk/benefit, and get the best outcome in several situations? And I’m really delighted that my colleague, Dr. Shail Vasavada, is going to share the second half of the presentation. The first half involves understanding some basic fundamentals related to the phaco machine, how do we remove the cataract, the nucleus, and also how do we keep the bag clean at the end of the surgery. So as regards the phaco machine, the lens material is removed first by a process of lens fragmentation. And that’s what is giving us the emulsate. And that’s why the phacoemulsification is the name. So the fragmentation can be done with longitudinal ultrasound, as it has been over the years, but in the last several years, torsional ultrasound, which Alcon has named — given to it as CarOzil or a torsional ultrasound — really has changed the way the lens is fragmented, and then this fragmented material is presented to the aspiration at the tip, at the phaco tip. And the way that fragmented material is aspirated is by two fundamental systems. One, very popular and widely used, the peristaltic system, which: First step is attracting the fragmented material to the tip by a process called aspiration flow rate. Slow or fast. And then once that material comes to the very tip, the vacuum generated in the same — so finally that vacuum removes the material out of the eye. That’s the peristaltic system. Versus the Venturi system, where in one process — there are no steps of removing the lens material, like attraction and then building the vacuum, as it was in peristaltic. Here in Venturi, straight away, the vacuum sitting in the machine, in the tube, attracts and removes straight away, in one step. Therefore it’s a little rapid, or faster than the peristaltic. But each of the systems has its own problems. Pluses and minuses. So let’s look at that. And the AFR or aspiration flow rate, the attraction, is by either the speed of the pump, and that can be slower, as slow as 12 cc per minute, with the phaco probe, or as high as 60 cc per minute. And then the vacuum builds up only and only when the material comes to the tip. Unlike the Venturi, where it’s straight away — the vacuum is already existing inside the tube, and therefore attracts and produces a little faster vacuum. But the real advantage of the peristaltic is that you can separate the attraction speed and then have the right vacuum. In other words, in a challenging situation, and Dr. Shail is going to speak on that, you can attract it very slowly. As slow as 12 cc per minute. 16 cc per minute, or whatever is comfortable, and whatever is necessary in that scenario. And then have the appropriate high vacuum. You cannot do that in Venturi. If you raise the vacuum, the safety will be compromised. So the real advantage of the peristaltic — and I think that’s the reason it’s being used very frequently or widely — is because you are able to separate the attraction flow rate from the vacuum. And this animation my colleague Dr. Vandanas showed years ago. 60 cc per minute. And even when a probe is not near to the iris, it catches, because of the shear speed. And the same actually, when she does it with 20 cc per minute. The iris doesn’t come to the phaco tip. That’s what the peristaltic aspiration flow rate is. But the key of the lens removal process is balancing the fluid going in and fluid going out. Input is by the bottle height, with the conventional machine, and newer generation machines, like Centurion, the bottle has a given height, but the fluid is pumped in by the pressure plate. So whatever the mechanism, the fluid going in has to be balanced with the fluid going out. The fluid goes out through the aspiration tube, which is aspiration flow rate. 20 cc per minute. 25 cc per minute. And also the wound leak. Fluid leaking out of the wound. Out of the incisions. And when the surge occurs, there is additional fluid exiting through the tube, which is known as an occlusion break response. So this should be balanced. But if there is no occlusion, even in an unoccluded state, we need to be careful of avoiding excessive wound leak — tight, good incisions — aspiration flow rate, if it is high, you must have a high bottle height, and if your aspiration flow rate is low, you must have a lower bottle height. Otherwise, there will be either low bottle height, low fluid, low input, or high input. Which will upset the pressure gradient inside the eye. But notice the wound leak from the chopper or a side port. We don’t pay attention to that, but the IOP will drop by 15 millimeters of mercury with such a leak. So you can understand the stability of the eye will be compromised. But the real question is: Do we really want to pay much attention and focus it on input/output balance? In other words, the fluidics, as it’s popularly called? Why? Because it does have a significant impact on the anatomy and the function of the various tissues of the eye. And I will present two studies to you, which we published — one in 2010. And we were doing it since 2007 or 2008, these things. And in that study, we did two groups randomly. One we used 40 cc per minute flow rate, with the 90 centimeter bottle height. And in the other group, we used 20 cc per minute, and 65 centimeter bottle height. And we found that the eye which had a lower bottle height and low flow rate used more fluid, did more clock time, and had to have more energy. But we could confine the lens removal process away from the cornea in that group. While in the higher flow rate of 40 cc group, we finished quicker, less fluid in and out, and less energy, but the best part is that when we looked at the cornea inflammation and IOP, on day one, the eyes with the lower parameters did much better. They had a clearer cornea, less inflammation, and less IOP rise. In spite of more energy going in the eye, more fluid going in the eye, and more time taken. So, in other words, it’s like driving. Driving a motorbike or a car — higher speed. Obviously, you will go faster, but you are risking your potential to make an accident. That’s what you see on the motorways for years. But the second study, it really was very interesting. And we could discover why we found that the lower parameters of flow rate and the bottle height gave a better outcome to the cornea. And the segment. It’s because the higher flow rate and bottle height were associated with higher intraocular IOPs. Up to 80-plus millimeters. And we recorded the live dynamic during the surgery by introducing the intracardiac sensor devices. So higher flow rates — really something we want to avoid for the impact of the eye, and you can understand the trabecular meshwork dysfunction, the macular cones and macular edema and epithelium and so on. So I think we, for one, are convinced that as low but as high as your efficiency allows. So in the good old days, the technique like slow motion technique, which used very low bottle height and flow rate, didn’t work well, because it took a long time. It was very tedious for the surgeon. But with the torsional ultrasound, because the material remains in the tip, this lower flow rate could compensate for the lack of speed. So the efficiency or the speed was not compromised, and still we could remove the fragments and the lens away from the cornea. So safety was added by these torsional components. And therefore lower parameters now are the in thing. And you could see on the screen, on the left side, the flow rate is 40 cc more fluctuations of the graph. And you can see that the gain there — that on the left side, there are more dips and more fluctuation. While on the right side, this process is a little slower, of course. But not that slow. Sufficiently fast. But look at the fluctuation. Minimal fluctuation on the right side, because the flow rate is 20 cc per minute, and the bottle height is low. So that’s what you want to keep in mind, understanding the machine. The nucleus, when you remove, has distinct phases. If you are doing a sculpting, and we recommend that, to create the space. And then divide, and then remove the divided fragment. Each of these stages has a distinct object to you, and therefore has different parameters, like the bottle height, the flow rate, the power, and the vacuum. Whatever you do, make sure it’s reproducible in your hand. It’s predictable every second of the procedure, and obviously at the end, very safe. Principally, simplified, there are two ways to remove the nucleus. Doing the four quadrant technique or sculpting, as we call it, or chop technique. Dividing with the help of a vacuum-based hold of the lens. The first example of a sculpting involves creating a trench or a space, and notice on your right hand side the parameters here — the IOP — 30. Which translate to 54 centimeter bottle height. Only 54 centimeter bottle height, mind you. And the flow rate is 14 cc per minute. And the vacuum is only 40 millimeters of mercury, with a 10% or 20% preset vacuum. Preset torsional ultrasound, on burst mode. 200 milliseconds, every time the burst is fired. So you take your time, and then the trench is made to your liking. So that is safe, because the flow rate is very low, the vacuum is low, and you can create four quadrants like this, taking your time. And this works very well every time, irrespective of the density, this works. It’s a universal technique, and I recommend that it is the best suited for soft cataract, but even when it is not soft, some cataracts which are not soft, not very dense, this is the technique, if you are not very familiar with the chop technique. I love chop. And I do chop technique all the time. But this is a very useful, very important, and very good technique. Once you divide, you need to be careful about the plane at which you’re removing. Try to be away from the cornea. And notice the parameters, once again. 40 IOP. About, once again, 58, 60 centimeter bottle height. 20 cc flow rate. And appropriate vacuum. So take your time. And it’s done in a very controlled manner. But it is the chop technique which is very useful, and reduces the energy delivery, and Nagahara came up with this concept of horizontal chop, which can be done without creating a space. Also known as a direct chop. And then Dr. Koch modified it, as stop and chop. We brought out for the first time what we described chop in situ, but then what was labeled as a vertical chop. And this is what the chop in situ — we published in ’96. We were doing it for two years earlier than that. Which involves occluding it, and then making the chop movement vertically, as you will see here. What I’m doing now here is that I buried the phaco tip here. The foot pedal here in second position, and the chopper initiates the crack, and then with level separation, that has been separated. You will notice it now again. My foot pedal here is in third position. So I’m entering the phaco, the lens material. Once I enter and occlude completely, I will bring my foot pedal to second position. Now you can see the second position. And once the preset vacuum is achieved here, I will depress the chopper vertically, towards the optic nerve, to initiate the crack. Not to aim total crack at this stage and then separate it with a lateral separation. So that’s what we described long back. But it is appropriately called vertical chop. In a denser cataract, you need to go even slower than that. And therefore, the principle of going a graduated way or a step by step way is very important in all aspects of lens removal. But particularly when you divide in this chop action, and this animation shows it. Occlude the tip, bury it, and then gradually initiate the crack, and extend this crack in a step by step manner, posteriorly to the very bottom plate. Which is very tenacious, in many dense cataracts, and then produce a lateral separation. And you’ll need to repeat this action all 360 degrees, and produce fragments of that hard cataract. And once you do that, you proceed to the next stage of the lens removal, which is the fragmentation. And there’s one more example of a very dense cataract. Notice the foot pedal here. The foot pedal is in one irrigation position. Now I’m going in a minute to the third position. I’m burying the phaco tip for the energy. And once that is achieved, I will come off to the second position, and the preset vacuum is reached here with the 700 here. It shows occlusion. My aim now here is to initiate the crack by depressing the chopper vertically, towards the optic nerve. The right hand remains still. And then reposition the chopper into the depth of the crack, and produce a lateral separation to create a total division, peripheral to the central, and anterior to the posterior. And likewise, the whole process is repeated all around. Sometimes this doesn’t work. So we devised a further modification, which is useful at times. You don’t need it every time. But that chopping principle applied at different levels is called multilevel chop technique. And it really ensures a total division. What it means is that you start the crack at the right plane, and then rebury it, take it out, and bury it again at a deeper level. And then apply the division force. Why we need to do that? Because in very dense cataract, the bottom plate is very resistant to the separation. And if you try to divide the bottom plate, working from the front of it, you need to torque the eye so much. So apply that at one level, and then go back to the deeper level, closer to the bottom plate. So your separating forces are minimized. So in a compromised zonule, in a bulky cataract, the bag is always straight, this principle is a multilevel chop. Really it has a very good advantage, that the zonules are not affected. So I am burying it, and producing an initial crack at one level. And I’m just doing that now. I can continue that, but this bag has a compromised zonule. So now I will take this buried tip out of the lens material, and then rebury it again, at a deeper level. You will see that in a minute. I’m taking it out, and then now again, I’m going at a deeper level. And apply my division forces closer to the bottom plate, so that I don’t have to use a lot of lateral separation principles. Whatever the technique you have, remember the endpoint of the second stage of this lens removal, which is division, is multiple and multiple fragments. The denser the cataract, the more the number of fragments that we need to do. Now, the fragment removal is the one which is very crucial, which will decide the clarity of the cornea. In a torsional ultrasound, unlike the longitudinal ultrasound, where the flow rate — where the fragmentation pushes the lens material away from the tip, as in a longitudinal ultrasound — the aspiration has to overcome that repulsional energy, or the push, and therefore you need to have a higher flow rate. In a torsional ultrasound, the material remains at the tip. Therefore both these forces work in harmony and synergy, so you can use the low flow rate and sufficient energy. This high speed photography, which my colleague, Dr. Sambhara Shivasa, produced — what we call the CarOziling, like torsional — the lens material remains at the tip. This is at a very high speed photography, showing what the torsional ultrasound can do. My left hand is steady, but the lens material gets repositioned all the time at the phaco tip. That’s what the torsional ultrasound does. And it enables us to keep the flow rate low and still achieve the efficiency. Phaco energy can be modulated by pulse mode or burst mode. Whatever you do, what matters at the end of the day — what matters to the clarity of the cornea and the anterior segment is the total amount of energy spent, which — the interrupted energy will help you to reduce. But two other important things: How much time you take to deliver. The longer you take to deliver the same amount, the better it is. 1 millijoule energy dissipated in 1 second, versus 1 millijoule in 2 seconds is better. 2 seconds. And also if you do it at the posterior plane, by which I mean the plane beyond the iris, it’s better than the anterior plane. This is the anterior plane. Even if you reduce the energy and spend less energy, this is more detrimental to the endothelium, versus the posterior plane, where you may take more time, more energy, but it’s away from the endothelium. So remember: Go slow. Be conscious of the plane that you remove. And the intraoperative OCT illustrates that. These fragments touching the endothelium from time to time. You’ll see here, coming here. And that’s what — it doesn’t look on the video here. You think it’s okay, but the trouble is once the red light goes up, and you are in the dead zone. So be careful of that plane of the emulsification. And finally, if more and more posterior capsule gets exposed, you need to keep your aspiration flow rate and vacuum low, but do not lift the phaco probe up. A common tendency is to keep the phaco probe up and up, as more and more posterior capsule gets exposed and more red glow appears. We are scared of rupture. So we are not changing the parameters. But we changed the position of the phaco probe, and bring it anteriorly. Instead of that, do not bring any phaco tip near the cornea, but use your parameters of particularly flow rate and vacuum. Now we, having understood the basics, I would request my colleague, Dr. Shail, to take us through the difficult scenarios and challenging situations that we all are eager to learn and produce a consistent outcome. So Shail, please. Take over.
December 13, 2019