Lecture: Optimizing your Pre-Operative Measurements and Phacoemulsification Parameters for Cataract Surgery

During this webinar we will review how to optimize the pre-operative measurements for cataract surgery. We will also review the phacoemulsification parameters and techniques designed to decrease energy expenditure and maximize surgical efficiency. The goal of this program is to optimize surgical outcomes whilst decreasing recovery time and improving patient satisfaction.

Lecturer: Dr. Kendall E. Donaldson, Professor of Clinical Ophthalmology, Medical Director, Bascom Palmer Eye Institute in Plantation, Florida, USA


DR DONALDSON: My name is Dr. Kendall Donaldson, and I’m a professor of clinical ophthalmology at the Bascom Palmer Eye Institute in Miami. I practice cornea surgery, refractive surgery, and ocular surface disease management here in Miami. So today what we’re gonna be talking about is optimizing your preoperative measurements and your phacoemulsification parameters for cataract surgery, so we can do our very best surgery each and every time we approach our cataract patients. I have a few disclosures listed here. So I wanted to start out with just a few preliminary questions to gauge where we are at the beginning of this talk, and then at the end we’ll come back around to these questions once again. So the first question: What percentage of cataract surgery patients have signs of ocular surface disease? We’re gonna give you 30 seconds here. A, less than 5%, B, 10 to 20%, C, 20 to 30%, D, 30 to 40%, or E, greater than 50% of patients. Just a few more seconds. So kind of a mix there. Most people said around 10% to 20%. Let’s go to the next question. Which formula below can be applied to most eyes undergoing cataract surgery? A, Holladay, B, Hoffer, C, SRK/T, D, Barrett, or D, Olsen. It’s interesting how this answer has changed through the years. It looks like most people are using the SRK/T and applying it to most eyes. One more question. All of the following are screening tools for ocular surface disease before cataract surgery except: A, tear osmolarity, B, pachymetry, C, MMP9, the Schirmer test, tear breakup time, or a questionnaire, the OSDI or the SPEED questionnaire. All of these would be appropriate, except which is not an assessment of ocular surface disease? So mixed, but most people said pachymetry. So let’s talk about making our best preoperative measurements for cataract surgery. Some people sent questions beforehand, so I want to answer those questions throughout the talk. Nowadays, people expect perfection from their cataract surgery. They have all had friends or family members who have undergone cataract surgery, or they may have had LASIK in the past. And we advertise to patients, as well as to each other, how great we are these days, that we can provide patients the very best vision with cataract surgery. So we have to be very careful in what we advertise to our patients, because we still have some limitations, although we’ve gotten better and better through the years. We really want to make sure we manage patient expectations after surgery. So if we look at the benchmark standards for cataract surgery, we see that 55% of patients are within half a diopter of the intended target, and 85% are within one diopter of the intended target, so that leaves about 15% of patients that are really outside of one diopter from our intended target. So there’s still some room for improvement there. So how accurate are we? I think if we look at the most common formula, which is the SRK formula, you can see the variables in this formula, and these are the things that can actually go wrong. Whether it’s the Ks or keratometry readings, the axial length, if there’s an error in one of these variables, it can throw off our IOL calculation for the patient. You can see one diopter error in IOL power can occur for each diopter error in a K value. So we want to be accurate with all of these measurements preoperatively, to get these measurements. So ocular surface disease is the number one source of error, and it’s also very common, as we’ll see shortly. This can affect both the power of the lens and the axis. We’re doing toric IOLs, astigmatism correction with our cataract surgery, so either of these errors can be devastating for a patient. We can have instrument error. Patients have LASIK, PRK, and now we’re doing cataract surgery. We make assumptions in each of these surgeries, and now they’re off because we’ve changed the shape of the cornea. We may use the wrong formula. If we use the wrong formula, we can be completely off with our IOL calculations. And number four, the index of refraction. This is being changed by any of our corneal refractive procedures, so we can have an error in the index of refraction, which would then be translated into an error in IOL calculations. So here are the formulas we’ve used through the years, and they’re kind of defined by the generation, where the fifth generation formulas are the most advanced. They really take into account the most variables in calculating our IOL. So you can see the older generation, the Holladay, Hoffer, and SRK/T have been modified to the fourth generation formulas. The Holladay II is a purchased software system, the Haigis, and then the fifth generation formulas can be applied to a broader group of eyes, the Olsen or the Barrett. The Wang-Koch adjustment can be applied to longer eyes, axial length greater than 26, you have to use this modification at the bottom. I like this illustration here. This is something I borrowed from Warren Hill. And you can see all the different formulas here, with the most advanced formulas at the bottom there, including the Barrett and the Hill. The Barrett II is the most advanced and the most commonly used, and is now being incorporated into most of our IOL masters, Lenstars, and other forms of IOL calculating instruments. The Barrett universal formula is really thought of as being the most advanced formula, that’s been the most well established, and can be applied to most eyes. So how do we get our very best numbers for these formulas? There are lots of different ways to measure the corneal surface. We can see here a bunch of topographic and tomographic devices. We’ve gone from topography, which is a two-dimensional way to measure the cornea, now to three-dimensional devices, called tomographic or tomography devices, which give us that third dimension in the cornea. So we really need to screen for potential complications before surgery, because any complications seen after surgery or error in IOL calculations seen after surgery is considered our fault, really, or a complication of the surgery. Where it may have been a preexisting condition that could have been missed. As I mentioned before, the number one reason or IOL miscalculation is ocular surface disease, and dry eye is really everywhere. It’s one of the most common things that we see in our general practice, but sometimes when we’re completely focused on the cataract, we might overlook some of these other things that are going on in our patients. So this can be a debilitating condition for many patients, and it can really affect our outcomes. And it’s really frustrating to us as surgeons, when we have our perfect surgery. The patient is 20/20, and they feel that our surgery is a devastating failure, because they’re irritated or struggling with their dry eye more after surgery. So they would think that’s our fault, if it were diagnosed for the first time after surgery. The international dry eye workshop, or DEWS workshop, was originally convened in 2007, and they’ve helped us with the diagnosis and the management and treatment of dry eye disease, and they met again in 2017, to really define how we should treat dry eye disease, and this treatment should be started before cataract surgery, really to optimize our measurements. We can see from this great study — this was a landmark study called the PHACO study, that looked at the incidence of dry eye in cataract surgery consultations, patients presenting for cataract surgery consultations. So 60% of patients never complained of foreign body sensation. However, on exam, about 63% had an abnormal tear breakup time, and you can see here also that a large percentage of the patients, 77%, had some degree of corneal staining, and so they did have some ocular surface disease that was either asymptomatic or undiagnosed, in just the routine cataract workup. So you can see 22% or one in five patients had prior ocular surface disease, and a lot of these patients are asymptomatic, and sometimes the questionnaires, as I mentioned before, can be very helpful in teasing this out. But you can see here that more than 60% had an abnormal tear breakup time, more than 50% had central staining, and Schirmer’s scores were also abnormal in many of these patients. Here’s another nice study by Preeya Gupta, also look at ocular surface disease in cataract pre-op patients. In this study, 50% had abnormal osmolarity, and 40% had corneal staining. Again, signs of ocular surface disease before cataract surgery. And there’s several other studies that have really documented this problem. We have lots of different ways to assess the ocular surface. As long as you use one or two ways, and you’re consistent with all of your pre-op cataract patients, then that’s what works for you in your clinic. But you should have some form of screening. I think questionnaires are really simple, in case you can do that in your waiting room, and that can be coupled with a Schirmer or osmolarity — in our office, we use an OSDI, which is a questionnaire, as well as MMP9 and osmolarity. So we have three ways, and we do that for all of our pre-op patients. But not everyone wants to spend money on some of those devices, so there are cheaper ways listed here. But it begins with the actual exam on the patients. Certainly we see here the irregular fluorescein staining. I like two-dimensional devices, like the Placido rings on the right. There are many manifestations. Patients can manifest in many different ways. So we have to ask. The OSDI and SPEED questionnaires are the most common, very quick ways to assess ocular surface disease. We have to take into account their other medications and systemic conditions that can impact the ocular surface. And slit lamp examination, with various forms of staining of the ocular surface that can help us look at various forms of ocular surface disease. So pick one and be consistent with it. The Schirmer test is a very simple way, not expensive, but it can help us really assess our patients, preoperatively. We do tear osmolarity on all of our patients. Again, you have to invest in this device, but we find there can be some irregularities with the results, so it works well when coupled with these other things. We use it along with the MMP9 and OSDI. There’s a great study that shows the effects of ocular surface disease or elevated tear osmolarity on both the power and the axis of our IOL calculations. So we can really see through this study that this can affect — non-treated dry eye — can really affect the power calculations and our axis, if we’re doing toric or astigmatism management, which has become more and more popular through the years. I find that 30% of my patients are asking for astigmatism management, during their procedures, and in a lot of practices, that may be even higher. There are many sources of error in our IOL calculations, but again, the number one source of error is a poor tear film and dry eye syndrome. If your corneal topography does not look perfect, reassess the tear film, treat the ocular surface, and bring the patient back at another visit for repeat tomography and topography. Not every technician is great at this. I have a few technicians that do all of our ocular surface measurements and all of my IOL measurements. Make sure the patient doesn’t get drops, that they’re not dilated, before we do measurements. When do we repeat measurements? Any time there’s an inconsistency. Very steep eyes, very flat eyes, if we see a difference in the corneal power. Eyes should be symmetric, so any time there’s an asymmetry between those eyes, we want to repeat the measurements and make sure they’re accurate. Any time the patient has high astigmatism, I want to repeat it. Again, small or large eyes. You can see here some areas of hot spots. That’s an abnormality. That should be repeated and verified, to see if it’s ocular surface disease, a Salzmann nodule, anterior basement membrane dystrophy. You can see the Placido rings, which are irregular. Those should be nice and round. Those are irregularities that indicate pathology. And here we see the hot spots, which are abnormal. That should be treated. Sometimes it even requires a superficial keratectomy for a Salzmann nodule. When I do that — all the time now, it seems — I do the procedure and bring them back a month later for repeat topography and tomography, and then repeat the measurements after they peel. We also have to identify — help patients identify the influential factors for their dry eye condition. Whether they sit at a computer all day, or other things listed here. They can really affect the ocular surface. So this is how we do our screening here in our office. Again, just being consistent. Find a way that works in your practice, and get your technicians on board, so everyone is doing the same thing. So that was the first thing I wanted to cover. Let’s stop. And a few people sent in some questions beforehand. So I do have a few questions that we can answer here. So the first question that we had received: How can we measure the exact astigmatism for a toric IOL? The way I like to do it, I do both tomography and topography, and we get an IOL master. The IOL master 700 is the most advanced, but I still think the 500 gives us excellent data. I match up all of those devices, and I like to see that those toric measurements are consistent with the patient’s manifest refraction. If there’s a big difference between the manifest and these other measurements that we’re making for cataract surgery, then that’s a sign that maybe either this patient needs some preoperative treatment for the ocular surface, or maybe we need to repeat the measurements. We just got another question. How long do you treat MGD before proceeding with surgery? If I diagnose MGD, I usually start treatment, and I’ll see the patient a few weeks later for measurements, I’ll look at the measurements at that time. If they look good at that time, we’ll go forward. If I’m not happy with my measurements, I’ll bring them back every two to three weeks. I find if I let them go too long, we feel we’re not actively working towards their cataract surgery. I don’t like to leave it too long. I like to see them back a few weeks later, to let them know we’re working towards this, and they haven’t just been left for six months. Another question: How long do you have to treat the ocular surface disease medically, prior to repeating the measurements? Every two to three weeks, I like to check them again. If I do a superficial keratectomy for anterior basement membrane or Salzmann nodules, I see them a month later for superficial keratectomy. And one other question that was sent in: How different can the topography measurements be from the manifest refraction before feeling uncomfortable about putting in a toric lens? I like to see those measurements be within 10 degrees of each other. So I really want to see consistency between multiple measurements. We do both topography and tomography, and I look at the manifest to make sure those match. Not everyone has all of those different devices. I really like the Pentacam. It’s a really nice device that shows us both pachymetry and gives us three dimensions, it gives us Scheimpflug images, and Placido. So that’s a nice tool. I really like the Galilei. But if you need just one device, the Pentacam does everything for you. So let’s move on to the next section now. Let’s get rid of those. So let’s spend some time on this. This is what I wanted to spend the bulk of this presentation on. So we’re gonna talk about the phacoemulsification machine, and how to really understand this, and I really think it’s important to understand how our machines work, in order to best set our parameters, and how to do our surgery most effectively. So I think we need to understand what phacoemulsification is. And where it came from. So actually, I think we all are aware that Dr. Charles Kelman came up with phacoemulsification, in his dental office. And this was learned from the procedures of cavitation. Similar to performing the removal of a cavity. With the implosion of microbubbles, creating waves of both heat and pressure, like a jackhammer type action there. So here are the three major principles of phacoemulsification. Number one is followability. We need to have a handpiece that’s going to attract those fragments back to the tip, as efficiently as possible. Then stroke length. That needle goes in and out of the tip of our phaco device, and so we can modify the stroke length, and that’s based on the power settings on our machine, to see how long we want that protrusion to come in and out. And then we want to make sure we use the minimal amount of power and energy to emulsify this nucleus. All surgery is trauma, and we want to make sure we’re performing the least amount of trauma to this patient as possible, to reduce the heat, to reduce endothelial cell loss. There is a huge range in endothelial cell loss, between poor surgery and great cataract surgery. So we’ll learn a little bit about that through my talk today. So this is a wonderful book, if you don’t have it, or haven’t seen it, I would definitely invest in it, or you can take Barry Seibel’s course. He offers it at most of the major meetings, like ASCRS, AAO, or you can get the book. He talks about all the principles of doing efficient cataract surgery. And I’m gonna share a couple of videos that I borrowed from Dr. Seibel. But he explains how fluidics work, to create a balance of inflow and outflow, so we can make sure the chamber is maintained, and that we’re performing efficient cataract surgery. So there are basically two components to phacodynamics. One is fluidics, and two is the release of ultrasound or energy into the eye. So let’s start with fluidics. So this is the basic phaco machine. All phaco machines are fluid-based, so we always have a fluid source, whether it be a bottle or some form of bag of fluid, and an irrigation line that’s taking fluid into the eye. The phaco machine allows us to pump this fluid through the eye, and this is coordinated through the use of a foot pedal. So in position one, we’re just irrigating. We have simply fluid. Position two on our foot pedal introduces vacuum. Now we’re able to suck fragments into our waste area. And then position three adds ultrasound. So then we’re adding phaco power, to actually break up the material in the eye. So this is the basic phaco machine there. And here’s our foot pedal. Again, I mentioned the three positions. We want to make sure we’re going to be efficient, not going into position three, until we really need it. So we don’t want to release any ultrasound, unless we should be in position three. So we want to use that position the least amount possible. So fluidics, as I mentioned, cataract surgery is all about the creation of balance. So the fluid in has to equal the fluid out, to maintain the space, to keep the anterior chamber inflated, because if we collapse the anterior chamber at any time, we’re going to kill endothelial cells, do iris damage, and prevent — and actually even cause vitreous prolapse, if we don’t maintain that space properly. We also want to create functional currents, to bring those pieces to the phaco probe as efficiently as possible, and we want to keep things cool, because if we produce thermal energy, we’ll produce a wound burn and kill endothelial cells. So this pump creates a vacuum and flow. There are two types of pumps. The most common type of pump, particularly here used in the United States, is peristaltic, and the most common in Europe is Venturi. But most pumps in the Alcon machines, the Infiniti or the Centurion, is peristaltic pumps. So there’s a fluidic pump, the fluid is pumped through this tube, and if we think about peristalsis, it works exactly like this, in the intestines. So we have rollers that compress the tube, milking fluid through the tube, and we have a drainage bag. This is our most common peristaltic pump. And occlusion is required to grip any piece. If we don’t have full occlusion here, we shouldn’t be releasing energy. So I always tell my fellows, don’t go in position 3 until you have full occlusion. You’re wasting energy, putting extra energy in the eye. Occlusion is essential for all peristaltic pumps. So we have various tips we can use, various angles. I find the more angled tips are very helpful, because with getting occlusion, it allows us to really have full occlusion there at the tip. So it increases the surface area here, basically, for occlusion, as we go to a 45-degree angle. So we can see here: It’s hard to get occlusion with an angle like this. We get better occlusion right here. We’ve turned the material, the nuclear material, a little bit. And we’re meeting it with 100% occlusion. That’s very effective. Okay. So again here, just emphasizing a non-occluded phaco tip — you shouldn’t be in position three. You’re releasing excess energy into the eye. So just make sure you’re completely occluded, because then your vacuum goes up. You’re sucking onto that piece effectively, and we can release our ultrasound most efficiently. In contrast to the peristaltic pump, the Venturi pumps, again, more of the pumps we see in Europe, this is based on compressed nitrogen, flowing over a rigid drainage cassette, as opposed to a bag, which we had, a non-rigid cassette, with the peristaltic pump. This creates vacuum as it goes from a high pressure to a low pressure system here, and the vacuum helps us suck those pieces to the phaco tip. Here you can see a non-occluded phaco tip. The vacuum is still high, so the followability is very good. With an occluded phaco tip, again, the vacuum stays high, but the fluid can’t get in. So the fluid is lower. As opposed to the fluid pump, which we saw with the peristaltic system, now we see this as vacuum-dependent. So here’s just a little table that helps compare the two pumps. The peristaltic, which is flow-based, versus the Venturi pump, the nitrogen based vacuum system. Remember, with the peristaltic pump, vacuum is created only on occlusion, whereas the vacuum is created instantly and constantly with the Venturi pump. With the peristaltic pump, the flow is constant until you get occlusion. Then the flow stops and we’re able to suck into our machine. So those are the major differences. I just wanted to briefly — on tubing size and tip size, you can see the flow is directly dependent on the radius of our tubing here, to the fourth power, and also the pressure gradient, which can be created through how high your bag is. Let’s go into that. So we can see that the flow is increased, as the phaco needle tip diameter is larger. So if we have a larger diameter tip, then the flow can be higher. Makes sense. And we can see here, again, we get higher flows with larger tips. But we have to watch out for surge. Surge can be horrible. That’s when you have a sudden collapse of the anterior chamber, if the outflow is greater than the inflow. Then we can’t keep our anterior chamber inflated, and we can cause damage, and we have a risk of capsular rupture. I’m gonna show you a video of this. This is actually a video that I got from Barry Seibel, who is the author of phacodynamics. He’s a wonderful cataract surgeon, and I could show you this entire surgery, which is really terrific. He’s a great phaco chop surgeon. We can skip ahead just a little bit. And I’ll show you a better example of phacoemulsification shortly, but you can see here, he’s doing his capsulorrhexis. Nice round capsulorrhexis there, that he’s pulling around with Utrata forceps. And he has this nice hydrodissection cannula here that’s curved. I actually use a straight one. But he’s able to reach out toward the periphery of his capsular bag and really hydrodissect nicely and turn, rotate that nucleus, really nicely, within the capsular bag, making the rest of the surgery much easier. So we have to remember, every step in cataract surgery is dependent on the preceding step. Having that perfect wound, making sure that you’re even comfortable, sitting there the whole time. It took me a while in practice to understand that my comfort and my positioning, making sure that I was gonna be comfortable, really made the whole surgery better for me. So every step is really dependent on the preceding step. So we’ll see here… Already, I saw a little bit of instability in his chamber, when he just went in there, and this is a little bit older video. But we’ll see here, he’s putting in his second instrument. So he uses a Seibel chopper. It’s similar to a Nagahara, but it has a curved tip on the end, which is beautiful. If you’re an early chopper, this is the way to go with this device. You see the rounded tip, so you can’t break through the posterior capsule. It can just glide over the posterior capsule. And you see how Barry reaches out to the periphery of his capsular bag, getting underneath his capsule edge. So make sure you can visualize the capsule edge. If you’re first starting with chopping, it’s nice to stain your capsule, use some Trypan blue to stain your capsule, I would say, for the first ten cases, just so you can make sure to get under the capsular edge. And I’m gonna show you some really nice videos of chopping. But this is a wonderful instrument to do early chopping with. He gets out there, and to the periphery, and he’s able to bring the chopper right into the tip of the phaco instrument. Again, don’t reach with the phaco probe at all. He’s keeping his phaco probe very central. That’s really important, to make sure you have safe surgery. When my residents or fellows start reaching that phaco probe out to the periphery, I start to get nervous, and that’s not safe surgery. So if you have to reach with something, you reach with your second instrument. Don’t reach with the phaco probe itself. The second instrument can bring your materials — you’ll see he’s kind of reaching around, and he’s just chopping again and again. The more chops you can put in there, the less energy you’ll need to manipulate those pieces. But you can use your second instrument to bring the material in. Look how the anterior chamber is very unstable now. You’ll see the iris kind of going down. So here is surge. This is a perfect example of surge. Watch how the anterior chamber kind of collapses at times here. The iris is going in and out. This is dangerous at this point. So he should have kind of stopped and said: Why is my iris going in and out? Why is my anterior chamber collapsing at times here? So what’s happening here is the sleeve is not the right size for his phaco tip. You have to figure out: What is going on? Is my wound too big? Do I have fluid leakage through the wound? Is my sleeve the wrong size sleeve? This is getting dangerous now. Especially since he’s removed several pieces. The pieces aren’t supporting the anterior capsule anymore. This is where capsular rupture occurs. When you have fewer pieces left in the eye, you have no support for the posterior capsule. And these last few pieces — the posterior capsule is gonna fly up, the anterior chamber is gonna collapse, and he could have posterior capsule rupture here. This is an unsafe way to perform cataract surgery here. A very bad example here. We had good examples of phaco chop, but we should have stopped to figure out what is the problem with this case. So that’s a great video that illustrated many points of phacoemulsification, what to do and what not to do. So the problem with surge: We don’t have a balance of inflow and outflow. The inflow is based on how high your bottle is. And you have two sources of outflow. You can have loss of fluid from your incision. Again, as I mentioned, look at your incision. If you have a bad incision, it’s too big. You get leakage. That will cause an unstable anterior chamber. So keep inflow greater than outflow, to maintain your anterior chamber volume. So briefly let’s talk about the physics of the tubing. So you can see here: Inflow tubing and outflow tubing are different. Let me just show you a little bit about this. I’m gonna go back to that slide in just a second. But occlusion of the tube happens here, and compliant tubing can collapse, and that will store energy, and post-occlusive surgery occurs when this rebound happens. We can see here this is the difference between inflow tubing, which is much larger diameter. It’s a soft tube. And outflow tubing, which is a rigid tube. Has very low compliance, and this is how all phaco machines basically work. Different companies talk about various advances in their tubing, but this is basically how they all work. So we can see here the inflow tubing versus the outflow tubing, and this helps create a stable anterior segment for cataract surgery. Enough about that. Everyone is trying to make their incisions as small as possible. So this is the difference between coaxial versus bimanual irrigation. We’ve been going toward the size of smaller incisions, but when we have smaller incisions, as I mentioned, the tip sizes and tubing sizes are smaller, so the flow is lower, slower. So everything happens a little bit more slowly. There are a lot of advantages to the split irrigation, instead of coaxial. I like to use a bimanual like this, when I’m removing pieces from underneath the wound. That last spot where you can really get some sticky cortex underneath the wound, so bimanual is really helpful in that kind of situation. I also like bimanual for femto cases, because they have sticky cortex, so I get better control with the bimanual irrigation. But I actually use the transformer device from Alcon, which allows us to use either coaxial or bimanual. So it allows us to switch back and forth as needed, and there are some benefits to each. So again, as I mentioned, with the small incision surgery, it’s great to have small incisions, but everything moves much more slowly. So we went through the issues with the tubing size. This is dependent on tubing size. The smaller our incisions, the smaller the tubing, the slower the flow. And we explained that before with this equation. So again, we see the radius, the diameter, basically. They’re directly proportional to flow in the fourth power, and again, the height of the bottle. So a high pressure gradient, if we elevate our bottle very, very high, we have a forceful entry of fluid into the eye. So we don’t want this to be a forceful jet of fluid, like a fire hose, so we have to modulate this. So again, we can raise the inflow within reason. We can raise the bottle. But we want to keep it at a reasonable height. If we go too, too high, then it makes — it increases the pressure of the fluid into the eye. So always keep inflow greater than outflow. Nice tight incisions are helpful. We have the restricted outflow tubing. So let’s go through the phaco machines. The Alcon Infiniti or the Centurion are the most commonly used, they have the market share in most of the world, although there’s also the Johnson & Johnson Signature, and the Bausch and Lomb Stellaris, more common in Europe, I would say. The Alcon Fluidic Innovations, both the Infiniti and Centurion. I use the Centurion, but a lot of people are using Infinitis. They’re both great machines. We talked about peristaltic systems. It’s very important to have an occluded phaco tip. It’s entirely dependent on the occlusion of the phaco tip. That helps eliminate the postocclusion surge, also. Alcon has done great things with their tubing. This is the difference with the Centurion. No longer is there a bag. We set the pressure, the IOP, at a certain level, so we don’t have to raise or lower the bag. Most people set their IOP at somewhere between 40 and 65. That’s pretty typical. And the pressure will be maintained at that level throughout your case, as opposed to having to elevate the bag to different levels, and the anterior chamber is very, very stable throughout the whole case. So that’s really been the biggest advance with the Centurion. So Active Fluidics, again, the surgeon selects the target pressure to be maintained throughout the procedure. You set your irrigation level, and your leakage flow rate, as long as your incision is tight. So you set these three things, and it keeps your anterior chamber very, very stable throughout. They’ve also introduced a new tip, called the balanced tip. It has both torsional as well as longitudinal phaco released, and it has the 45-degree — we talked about the angles of the tips. And it swings back and forth to help introduce that torsional component, really to make the ultrasound release much more efficient. Okay, that’s what we see here. So when we switch from the Infiniti to the Centurion, we see a 38% reduction of energy dissipated during phacoemulsification. There have been several studies that have also shown that same reduction in energy usage, with the Active Fluidics. Johnson & Johnson has both the Sovereign and the more recent Whitestar Fluidic Innovations. They basically have a device — they call it CASE, or Chamber Stabilization Environment. And basically what this does is it is software that helps anticipate the occlusion break, and it proactively just drops the vacuum level, so that you can help eliminate surge. So you can see here when the occlusion breaks, then the vacuum goes down. That’s when you would get surge. But through the CASE system, it cuts that in half. So you don’t get as much of an instant drop in the vacuum, to help make that safer. And this system is very nice, because you have both the peristaltic and the Venturi options. Sometimes the Venturi can be really helpful. The followability is really helpful with the Venturi system, so a lot of surgeons like this ability to go back and forth between the two types of systems. This is their phaco tip. Again, most of the tips are now able to have both transverse and longitudinal modalities, to try to improve efficiency of just breaking up that piece of the cataract material. And this is B&L Millennium and the Stellaris. They really advertise their restrictive outflow tubing. Every company has their own tubing, but this, again, helps to prevent surge. Create a stable anterior chamber. Again, keeping the inflow greater than the outflow. The key thing is being efficient with both the peristaltic and Venturi systems, and it allows both coaxial and bimanual ways to perform your irrigation and aspiration. So then there are ways to modulate the release of energy. And I want to just spend a little time talking about ultrasound energy. So this is the main source of trauma during cataract surgery. So this is where we’re introducing the energy, and the length of the stroke creates the mechanical impact into the nuclear material, by cavitation, as we mentioned before. But also creates heat as a side effect. So we can set several variables. We can set the frequency of the impact and the length of the stroke, and then the movement of the tip, basically, while delivering that stroke. This again is cavitation, similar to dentistry, as we mentioned, that Dr. Kelman noticed originally. But it’s basically like a jackhammer effect, releasing energy into the eye. And we want to release the least amount of energy, use the least amount of ultrasound possible. We can burn the cornea in seconds. Fortunately with all of these innovations, wound burns are very uncommon these days, but still in a very dense cataract this can happen. So we want to make sure we have good flow, and we want to make sure we maintain our anterior chamber, and use the lowest power settings that we can to get rid of this cataract. So we want to make sure that we can decrease our phaco time. Basically that’s our goal. This will cause less trauma to the corneal endothelium, minimize endothelial cell loss, and prevent pseudophakic bullous keratopathy, giving the patient the best vision as quickly as possible after cataract surgery, which is what patients expect these days. They really want to see well right away. Patients want better cornea to be clear as early as postop day one, and I find in some of my denser cataracts, where I can anticipate the cornea is not gonna be clear the first day, I try to tell them that ahead of time. Your vision is gonna be blurry for a few days. This is a special type of cataract surgery we’re doing, maybe pupil stretching, synechiolysis, 4+ hypermature cataract. But if the vision is not gonna be good, I like to tell patients that ahead of time. We want to keep our phaco time down as low as possible and protect the corneal endothelium. Lots of good quality viscoelastic is really key, and decreasing phaco time. So what are the components of absolute phaco time? We said we want to keep this as low as possible. This is a measurement of the total phaco energy delivered to the eye during our surgery, and so we can see it’s a combination of the time that we’re releasing the energy into the eye, and the power. So we want to decrease both the time and the power that we’re releasing this energy, and so we can see — we can have a very short time that we release phaco power, at high power, and we still end up with 15 seconds of phaco time, absolute phaco time, or we can have a very long time in the eye, at a very low power, and we still end up with the same amount of ultimate energy in the eye. So again, we want to decrease the absolute phaco time by decreasing both these things, ideally. So how we do this… So there are lots of keys to doing this. The mechanical nucleus disassembly, using chop techniques instead of grooving a lot. Every time we groove, we’re releasing energy into the eye. Divide and conquer is great, it’s certainly a great way to be starting out, a very safe way to start out, but as we progress on to more advanced techniques, stop and chop is really nice with a central groove. I’ll show you a video of this, and then using chop for the remainder. That’s a great transition, from divide and conquer to stop and chop. I don’t do one-handed phaco. I don’t recommend it. I think it’s unsafe. Certainly some people are excellent at it, but I think most people do two handed phaco, and it’s nice to have a second instrument to protect that posterior capsule and help bring the nuclear material to the phaco tip. As I mentioned, ideally we want to keep the phaco tip in the center of the eye as much as possible, and do all our manipulation with the second instrument. Before this starts, I just wanted to acknowledge David Chang here. His picture is up in the upper right hand corner. He was the originator of phaco chop. But I really love this video by Brian Kim, which is one of the best videos of phaco chop that I’ve ever seen. I want to share this with you. And Brian does narrate this. So let’s let him show you this.

>> A step by step exploration of how I place my chopper and phaco tip during my phaco chop technique. This is a schematic of the eye. The pink is the phaco tip and the chopper is in black. As you can see, the phaco tip is placed subincisionally within the anterior capsular opening. The tip is slid down into the epinuclear material, but outside and around the endonucleus, and holding the endonucleus at the same level. The chopper is placed at the same position on the contralateral side. This is the Alcon balance tip. But I flip it 180 degrees, so that it’s beveled down. And you can see when it’s beveled down, there’s actually a little bit of a curvature to the phaco tip, and I use that curvature as the part that actually touches the lens as I fracture it, pushing it…

DR DONALDSON: And most people don’t do that bevel down. That’s the only comment I would make there. Everything else, I think, is wonderful. That’s a little tricky, and you’re higher risk for a posterior capsular rupture. So I wouldn’t go bevel down. I would use it the regular way.

>> Forward. This is the proper position of the chopper, when I go into the eye. You want to stay in a pronated position with your wrist, and then you supinate your hand, so that the chopper tip is facing you, when you initiate the chop. So again, pronation, supination, I like to go in the eye, pronated, and just to show you… I’m going in with one hand. Sliding the chopper in the pronated position, down into the epinuclear material, underneath the anterior capsule, rotating my hand, so that it’s supinated now. This is the ready position for the chop maneuver. Just for illustration, I’m going back out. Pronated, and then supinated back into the equator, and I’m in the ready position to initiate the chop. The phaco tip — again, it’s within the anterior capsular opening, and I dive down into the epinuclear material, but I note I’m outside of the endonucleus, but at the same level, I’m bringing the two instruments together in the center, and the chop is initiated without difficulty. The cross chop — same maneuver of pronating and supinating the wrist. And then bringing the chopper into the middle, and fracturing. This is another…

DR DONALDSON: Just to comment, only because there was a question written in about the settings on the phaco machine for chopping. So you can see his vacuum is very high, so he can really get occlusion of the material when chopping. So that’s super high. I usually use about 575 for vacuum. And when you’re doing chopping, I would also recommend a burst technique. So that really helps you get good occlusion, so that you can then hold onto the piece, as you’re bringing your second instrument in to the phaco tip. So high levels of vacuum and burst for chop mode will help you get good purchase on the nuclear material, so then you can do all your work with the second instrument.

>> For example, again, I’m in the pronated position, going into the eye. Sliding under the epinuclear material, rotating my hand. You see I’m nudging the lens, just to prove to you that I am indeed in the equator. Because I’m in the equator, when I do that maneuver, the lens jiggles. The lens moves within the horizontal plane. If I’m on top of the lens, as I’m showing here, when I try to supinate my hand, all it does is cause the lens to tiddly-wink, and it doesn’t actually move horizontally. Again, I pronated my hand, I went out underneath the anterior capsule and I supinated. I’ll do that again. After I clean up this epinuclear material with the phaco. Again, pronated, slide it past, the anterior capsule, supinate it, the chopper tip again —

DR DONALDSON: Okay, so let’s move on, in the interests of time. How to decrease phaco time and energy? Less time on the foot pedal. Avoid III unless you really need ultrasound. Let’s move on here. Decrease our power settings. How can we decrease our power settings? Fortunately all of the companies are developed advanced power modulation software. So we can have times when we’re not releasing any energy, and the energy can be released in packets like this. Okay? So again, we want to keep our phaco tip as cool as possible. Release the least amount of energy. And each surgeon can customize this, and all of the companies are willing to come out and help you customize your parameters. So we can see the difference between continuous phacoemulsification, as you press down on the foot pedal. The energy increases. With pulse, you can see these packets of energy being released, with breaks between each packet, and as you push down on the foot pedal, you get increasing amounts of energy. And burst is an equal amount of energy released at intervals. So that’s the difference between pulse and burst. Here’s phaco continuous. Again, constant energy delivery. Here’s pulse. Again, ramping up, but little breaks between. And then burst. All the same amount of energy each time, but having intervals in between. So all of these can be set, and really customized, and I would encourage you to have your representative from whatever company it is come out and help you make your settings, and optimize your settings for you. Okay? So you can have these hypersettings, which are advanced. The pulse modes, up to 120 pulses per second. And burst mode, duration as low as 4 milliseconds. You can set your duty cycle, how long it’s gonna be on, versus off, and there’s some pulse shaping I want to show you in a second. So here again we’re conserving energy, by having some packages where we’re releasing energy, and times when we’re not releasing energy. And that can be really modified, for each individual surgeon. So you can see here also you don’t magically decrease the phaco time. We can have the same amount of phaco time here. Here we have a large delivery of energy only twice, but that’s equivalent to all these small packages, delivered more frequently. So that just kind of explains the same thing that I just mentioned. So this is all dependent on the duty cycles. So you program how much time you want the energy on, versus how much time you want the energy off. Okay? And these are examples of variable duty cycles, again, just customizing it for each individual surgeon, trying to reduce the amount of energy delivered to the eye. So this is an example. On 20%, off 80%, or 20% duty cycle. And the benefits, again, we’re reducing energy placed into the eye. And this is just some more examples on different ways that your duty cycle can be arranged for you. You can also do pulse shaping, where you can have a ramp up. Again, another way to reduce energy, so here we’re reducing this amount of energy here. So that could also help with your efficiency. Any way to — here you’re using a pulse pattern. And cooling between. You can change the off times between there. Okay? So these are just other ways to reduce the amount of energy. Again, customizing it for what works best for you is really key, but getting best purchase, especially if you’re a chop surgeon, you want to use some bursts, or pulse, but usually burst, to really hold on to that piece, to allow yourself to pull into the phaco handpiece. Okay, so we want to reduce the repulsive effect. So that’s one of the advantages of the variable rise time, and also that’s why I use burst, to kind of get in and embed into the piece, before I just use a bunch of power, which is going to push away my nuclear piece. So this is more just explaining what I mentioned. Again, you want to customize or tailor fit this to what works best for you, and the reps can help you try a few of these different things, to really decide… Okay, if you want to add some burst to help with chopping, that can be helpful. So let’s look at a couple examples here. This is just a very basic, nice starting point for basic divide and conquer technique with cataract surgery. So this is a great starting point. He’s got a nice wound, he nipped the capsule, and now performing a nice round capsulorrhexis. It’s all about your view, and again, your comfort as well. So take time to find how you would like to be positioned. Use your lighting, so you can see the capsule properly. Fiddle with your lighting at a time when you don’t have a patient there, so you can see how you can use a better lighting, different angles, for the red reflex to be improved, so you can really visualize your capsulorrhexis. Because if you can’t see, you can’t perform adequate safe surgery. So perfect capsulotomies. As I mentioned before, every step is dependent on the step before. Nice hydrodissection, when you see that nice fluid wave behind the nuclear material, and here again, this is a basic divide and conquer, so we see a nice groove… And again, he’s using a Seibel chopper here, even though he’s doing divide and conquer. This is useful for soft lenses, but the Seibel chopper is really a nice tool, and you can do both divide and conquer and chop maneuvers with this. So you’ve got a beautiful crack there, and just gonna safely rotate. You can use both instruments to rotate. Sometimes if I have really loose zonules, I’ll use the two instruments together, and really kind of use them to help avoid torque on the lens there. So again, you can see he’s got the two instruments pushing apart from each other. Got a nice crack. Of course this doesn’t always work this easily, but this is the perfect patient and the perfect divide and conquer example here. So really taking his time, pushing out with the second instrument at the periphery. To rotate that really nicely. And again, we saw that he had beautiful hydrodissection here, so the nucleus just rotates really nicely. And again, putting both instruments across from each other to separate, and then so now it’s easy… Of course, sometimes you can run across a posterior plate, or things like that. So that’s our basic technique. Okay, so let’s go on to the next. So this is David Chang. This is wonderful.

>> This is Dr. David Chang, with an instructional tape on phaco chop. The classic Nagahara method of phaco chop begins with inserting the chopper peripherally beneath the anterior capsule. I will hook the equator, after impaling it centrally, phaco here in the burst mode. See the two bursts. Once I hook the equator, you chop toward the tip, a slight separation, bisect, after rotating the nucleus for a few clock hours, (inaudible) the most difficult step is certainly the first chop. The most difficult piece to remove is the first piece. Once this has been done, each subsequent piece becomes easier to chop, to remove, because the patient has a very loose zonular complex. This is something that is a common problem with exfoliation, trauma, and you can see that I’m unable to rotate the nucleus. You can see how lose the zonules are. This is an attempt to rotate it with the hydrodissection cannula. In this case, the capsular bag is so poorly anchored that it actually just wants to rotate with the nucleus. So now what do we do? One advantage of the microfinger, again, is the versatility in placement. So a nucleus that I cannot rotate, it’s barely firm, as you can see here, there is the compression, the initial chop in half, without any sculpting at all, and now what I’m gonna do is simply cross over a few clock hours to the side, and chop again. And so although the phaco tip can’t really be placed in multiple different positions, the microfinger with the side port can.

DR DONALDSON: So let’s move on, in the interests of time here. This is just a quick example of stop and chop. So the stop and chop, we have a central groove. So this is a nice transition from divide and conquer to chopping. This is a Nagahara, which I think is safer than the microfinger that you just saw David use. The microfinger works great in his hands, but I really like the Nagahara. You’re turning the tip of the Nagahara to go under the side of the capsule. Reaching out. This one is kind of sticky, but getting it. Let’s turn it around a little bit. Hang on one sec. Again, doing all the manipulation with that second instrument. Not with the phaco probe. And then using the second instrument to kind of feed that piece into the phaco tip. So you have the central groove, and using the second instrument to do the chopping. From there out. High burst mode, high vacuum, 575, and reaching around with the Nagahara. The more chopping you can do, the better. You’re putting less energy in the eye, so you can chop as many times as you want, to get those pieces as small as possible. This is another stop and chop example, so we’ll skip that one. I want to show you what not to do. This is a resident case, one of his first phacos, and he’s using a Drysdale, one of the first instruments — just kind of pushing things around. I really think the spatulas like the Koch spatula or the Drysdale, that are flat, are nice for a really soft lens, but in this case it wasn’t helpful. This case went two and a half hours. And the longer you’re in the eye, the smaller the pupil gets. He had some bleeding, of course, and that type of thing. Long cases — nothing really good happens in the cataract surgery after the first ten minutes. If you’re in the eye for two and a half hours, something bad is happening there. But again with the Drysdale in this case, he was pushing around and not being effective. We can skip over MiLoop in the interests of time, but I find in very dense lenses, a lot of time, the MiLoop is very helpful. I use Trypan in this case for teaching purposes, so we can see how the MiLoop fits under the anterior capsule. We’ll watch just a few seconds of this. We don’t have to watch the whole thing. I don’t know if you’ve seen MiLoop before, but it can be helpful in dissecting the nucleus. It was bought by Zeiss, and we’re slipping this ring, a nitinol ring, under the anterior capsule. You can see the MiLoop is into the level of that black line, and it’s sweeping underneath the nuclear material. It goes all the way across. You can barely see it here. But if you look very closely, you might be able to see it behind the nucleus. I went all the way across, and once it’s gone all the way across in the sweep, you go back to the center. Back to the center there, and always use a second instrument at this point. Otherwise the MiLoop will drag the material into the anterior chamber. So we’re gonna use a second instrument, a Nagahara here. Just to hold that nuclear material back. As you close the loop, it doesn’t drag material into the anterior chamber, near the endothelium. Okay? So that’s basically the principle of the MiLoop. So to become a better phaco surgeon, ways to disassemble the nucleus mechanically, less time on the foot pedal, decrease your power settings, use these more advanced techniques that will allow us to have times where we’re off of the energy release modes, and use the advanced power modulations, and fluidics is all about balance. Maintaining a stable chamber in which to work. So you need efficient fluidics, efficient phaco power, and that results in efficient surgery, clear corneas, and less traumatic surgery. So let’s go back to the questions we started with, and let’s see what everyone thinks at this point in time. Our first question: What percentage of cataract surgery patients have signs of ocular surface disease? Is it less than 5%? 10 to 20%? 20 to 30%, 30 to 40%, or greater than 50% of cataract patients? So still you’re saying 10% to 20%? It really is greater than 50% who have some form of ocular surface disease, and that’s been shown in several studies now. Number two, which formula below can be most broadly applied to most eyes, without adjustment? A, Holladay, B, Hoffer, C, SRK/T, D, Barrett, or E, Olsen? So Barrett increased a little bit, but SRK/T is still the one that got the most there? It’s actually the Barrett formula. It works well in long eyes, short eyes, and regular length eyes as well. And finally, all of the following are screening tools for ocular surface disease before cataract surgery. A, tear osmolarity, B, pachymetry, C, MMP9, D, Schirmer test, E, tear breakup time, or F, questionnaires, like the OSDI or SPEED questionnaire. Perfect, so it’s actually pachymetry. So 69% of you got that one. Perfect. So we had a couple additional questions that came in. So let’s see. Do we need to take k readings with both manual and optical keratometer? If taking both, which do we need to take into consideration? Honestly, I haven’t done manual keratometry in a long time. I think it’s become sort of a lost art. We still have a manual keratometer, and as long as your technician or you yourself do it consistently, and you use the same device all the time and you’re good at it, I think that’s a great device to use. I would still use another topographic or tomographic device as well. So it’s good to have a number of measurements. So I would use both, but also a topographer or a tomographer along with your manual. How is low CDE directly related with high vacuum and flow of active fluidics? The CDE is calculated by a formula. And that is determined by the vacuum, the phaco time that we talked about. So CDE is important, and it does take into account all those things that we’re talking about here. The vacuum and the level of — the amount of time that ultrasound is released. But CDE isn’t the whole story, though. We want to keep our CDE down as low as possible, but lots of other things are important. For example, the size of the anterior chamber. Patients that are hyperopic, small eyes, just that space in the anterior chamber being smaller, causes more trauma to the corneal endothelium. Using proper viscoelastic is important. Performing cataract surgery in the bag, instead of doing all this in the anterior chamber, so proximity to the corneal endothelium, is very important. So it’s not all about CDE, but I do pay attention to CDE pretty closely, and I try to keep it as low as possible, during my surgery. So is pulse mode effective in the Centurion? Which power modulation would you recommend? I think pulse mode is great. Again, I use it with the Centurion all the time. I don’t like to release continuous phaco energy. So I think pulse is very important. So I would recommend both pulse and/or burst. Any tips for removing the epinucleus? I would say the biggest tip would be having a good hydrodissection. Again, as we mentioned before, each step is dependent on the one before it. So if I have trouble removing epinucleus, and it’s really sticky, sometimes I’ll go back and I’ll hydrodissect again, just to loosen it up again. If I’m really having trouble getting it out, like I said, I use the Transformer, so I can switch, if I’m already in to I/A, I’ll switch and use bimanual. If it’s really epinucleus, though, and I’ve already gone on to I/A, sometimes I’ll go back and use the phaco tip again, and use my epinuclear setting on the phaco tip. Or use a second instrument to kind of poke it into the tip. Let’s see. Another question was: If you’re a chop surgeon, are there any benefits of the MiLoop over a chop? As much as I like the MiLoop, I find it takes me a little bit longer to use it, and I think if you’re already a good chop surgeon, the MiLoop isn’t that helpful in most cases. It’s just an extra step. When I find the MiLoop to be most effective is in a really, really dense cataract. Some of those 4+ brunescent NS cataracts have a posterior plate, and in those cases, if you have really good hydrodissection, and you can get the MiLoop around to the back of it, it’ll get the posterior plate really nicely. So that would be an advantage over just a regular chop, but in a routine cataract, if you’re a chopping surgeon, the MiLoop doesn’t have much advantage. It’s just a routine cataract. So there’s a question about: Is the incision location of any significance? A lot of surgeons will change their incision location based on the astigmatism that the patient has. I don’t do that at all anymore. I used to try to do that. But then I would find that I was uncomfortable operating in a position that I’m not used to. So now I much prefer to control my astigmatism with either limbal relaxing incisions or with a toric lens. My limbal relaxing incisions — I open 100% of them at the time of surgery, because I find that I don’t get enough effect if I don’t open them. And I go to 90% with my limbal relaxing incisions, but I don’t change my incision location. We did a study a while ago that showed that surgeon induced astigmatism is only 0.11. It’s so small anyway, and I don’t want to move it too central, because I’m afraid I’ll introduce some irregular astigmatism. So I don’t like moving the wound. And what grading system do we use for describing the opacification for the lens? We all sort of use the LOCS system, and it’s gone through several modifications over the years. If people really use the LOCS system properly — probably most of us don’t. But within your practice, you can consistently use it the same way. But I think most of us aren’t using the LOCS system, even though that’s the most up to date system. I think most of us aren’t using it accurately. One more question, and then we’ll wrap it up. My opinion — why are certain surgeons still performing extracapsular cataract surgery, instead of phacoemulsification? Well, perhaps they never became comfortable with phacoemulsification. I find even in the very densest cataracts, I still am able to do phacoemulsification 99.9% of the time. Although sometimes I cheat a little in some of those dense lenses. I will use the MiLoop, I will use the femto laser to help me. So I use those extra tools in really dense lenses. I haven’t had to do an extracap — probably one in the past year. But I think extracaps are pretty rare. Sometimes I’ll use an extracap in conjunction with a PK, doing an open sky extracap in a really dense lens, when I can’t see into the eye at all. So that’ll be the last question, and I really appreciate you all joining today. And I hope this was helpful for everyone. And thanks to Dr. Barry Seibel and Uday Devgan, who helped me with some of these slides today, and some of the videos. Thank you very much.

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June 13, 2019

Last Updated: October 31, 2022

2 thoughts on “Lecture: Optimizing your Pre-Operative Measurements and Phacoemulsification Parameters for Cataract Surgery”

  1. My dear how are you ,I’m fine and you.I want attend your lecture but the lecturing time difficult to me because of I am busy on lecturing time.How can I follow ?


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