The ins and outs
of bimanual phaco

With interest in bimanual phaco on the rise, cataract surgeons discuss its fine points.




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Stephen S. Lane, M.D.: Dr. Chang, what is your interpretation of the definition of bimanual phaco? Should we call it something different other than bimanual phaco? I've heard the terms microincision cataract surgery (MICS) used. I'd like your opinion as to what it should be called and what it involves in terms of instrumentation?

David F. Chang, M.D.: If the goal is to downsize our phaco incision size, we have to dissociate the irrigation sleeve from the aspirating phaco needle. That's why the term bimanual phacoФ fits pretty well, because it describes that we're separating the irrigation and the aspiration instrumentation.

Terms, such as microincisional cataract surgery (MICS) highlight the fact that bimanual instrumentation reduces incision size. However, aside from incision size, an important question is whether there are fluidic advantages with this system, compared to coaxial phaco.

The renewed interest in this concept was kick-started by the Sovereign WhiteStar technology (Advanced Medical Optics, Santa Ana, Calif.) because I think most of us would have assumed that the real danger in doing sleeveless phaco was a wound burn.

Part of the impetus for developing cold phacoФ instrumentation that is to say technology that gives us a big margin of error with respect to incisional heat was to enable us to dissociate the irrigating sleeve. Surgeons are showing that you can do this with other phaco machines as well.

Lane: Does anybody else have anything to add to this in terms of other instrumentation or other parameters that would qualify or constitute bimanual phaco?

Mark Packer, M.D.: I would add some parameter of incision size to this. If you do a literature search for bimanual, you end up with articles that discuss coaxial and the use of a second instrument, as opposed to one-handed phaco. I think that's a bit confusing. I think also there's some implication about incision size sub 1.5. We use 20-gauge instruments and 1.2-mm incisions, but I think that where there's an implication about incision size that needs to be some part of the definition as well.

Roger Steinert, M.D.: I don't think the term bimanualФ covers it because that alone doesn't convey what we're talking about. I think what captures peoples' attention is the small incision.

Lane: Dr. Mackool, I know you've discussed cold phaco before. Is it fair to use the term cold phacoФ for any type of phaco that we do with ultrasound?

Richard Mackool, M.D.: There's no question that if you reduce the duty cycle of any instrument, you'll decrease the temperature of the instrument. In other words, it's releasing less energy per unit of time, so the temperature of that tip is going to be cooler than one that has a higher duty cycle.

Lane: Safety is certainly one of the major issues around any procedure that we're doing. What are some of the safety concerns surrounding bimanual cataract surgery?

Packer: I think a large safety issue has been maintenance of the chamber.

One of the early problems that instrument developers encountered was getting enough irrigation flow into the chamber to maintain a stable chamber. When you have a 20-gauge instrument whether it's an irrigating chopper or an irrigating manipulator you need as big a lumen as possible to get an adequate flow in there. That flow needs to be higher than your aspiration flow, significantly higher, in order to maintain the chamber.

A large change has been with instrumentation. Microsurgical Technologies (Redmond, Wash.), ASICO (Westmont, Ill.), and Rhein (Tampa, Fla.) have made irrigating choppers that provide adequate inflow.

One of the things that we have to do in order to get adequate flow is raise the bottle all the way to the ceiling, or in the case of the Millennium (Bausch & Lomb, Rochester, N.Y.), which has a module by which you can pressurize the bottle, use that feature, and then have the bottle lower.

Chang: The one thing that has enabled me to use a higher vacuum is the Cruise Control device from STAAR Surgical (Monrovia, Calif.). This disposable device can be attached to any machine's tubing to create a significant flow restriction that reduces surge.

Steinert: I don't know that I do anything differently, but I have not found that the fluidic balance is nearly as marginal or critical as we have all believed. I've gone back to 19-gauge. Although I do have my bottle height very high and I try very hard not to have excessively large incisions, I have not found chamber fluctuation to be a particularly big issue, at least with the Sovereign unit (AMO). Going back to 19-gauge bimanual has not slowed me down.

Lane: Do you feel that bimanual phaco right now is as efficient as coaxial phaco?

Steinert: Yes, if I use 19-gauge.

Lane: So the time period that it would take you to do a typical case is roughly the same amount of time that it would take you to do if it were a coaxial case?

Steinert: Yes. And perhaps even faster because I do think that the bimanual instrumentation, if it's optimized, actually gives you more control in terms of maneuverability of the fragments. The key is to be truly bimanual.

Lane: Dr. Mackool, tell me about efficiency? What are the drawbacks with the bimanual phaco as opposed to coaxial?

Mackool: I find that I am currently slower with the bimanual technique, compared to the coaxial technique. I can perform bimanual with the Alcon Legacy AdvanTec using 40 cc a minute flow rate and 250 mm of vacuum. With the Infiniti, I would look at about the same flow rate and a higher vacuum level of 400 mm Hg for nuclear segment removal. It is possible to use the higher vacuum level with the Infiniti because of the reduced compliance in the aspiration component of this system.

There is no comparison between the amount of fluid that is generally required for the bimanual procedure compared to the coaxial procedure.

Currently, my phaco incision during the coaxial procedure is sealed (I use the Mackool hand piece by Alcon), and therefore there is no incision leakage around the phaco tip. My side port incision is very tiny (about 0.5 mm external incision and 0.25 mm internal incision, tapered), so there is minimal leakage from the side port incision.

The net result of this is that I remove the nucleus using only 13-31 cc of fluid with the coaxial technique. With leaking bimanual incisions, coupled with the fact that lower vacuum levels are used and nucleus removal therefore takes longer, it is virtually impossible to use less than 100 cc for nucleus removal at the present time.

Lane: Dr. Steinert, do you find that you're using more irrigation fluid with bimanual than you do with coaxial?

Steinert: No, I don't. I think that's an incision size leakage issue.

Lane: And, Dr. Mackool, you use Mackool needles (Alcon) to allow for a tight coaxial incision, correct?

Mackool: Yes. I'm using a 1.1 Mackool flare tip through a 2.75-mm side incision. The side port incision is just about 0.5 mm. It is actually tapered, so it's a real tiny side port that's hardly leaking.

Lane: I think you'll find that you're going to, by the nature of making these tight incisions for bimanual, reduce your overall fluid usage.

Mackool: I would agree. Compared to the 3.2-mm phaco incision of the past that would leak 20cc, 25cc a minute, and required the surgeon to change the bottle during most cases, we are doing much better. The literature typically reported surgeons using 250-350cc used per case. We could do 10 patients with that amount of fluid today.

Chang: Dr. Lane, if you had asked me this question a year ago, I would have said, hands down bimanual takes longer.

Beyond the increased operative time, having to turn my aspiration flow and vacuum rates down, was a real tradeoff and disadvantage. But again, since I have been able to work at my usual high vacuum rates with the Cruise Control device, the fluidic gap has closed considerably.

The one thing that still bothers me the most is that the chopper is more constrained when we're doing bimanual phaco. It has a much broader shaft, there's more tendency for oar locking, and it's somewhat tethered by having the tubing attached to the end of it. So I think that slows me down a little bit in terms of efficiency and speed.

Lane: Dr. Packer, do you want to speak to efficiency?

Packer: In terms of the total amount of time that the case takes me now that I've done this for over a year, it's identical to the time that I was taking before with coaxial. So the overall operating time is unchanged.

I have seen a reduction in effective phaco times. We're collecting this data now, and I know there are all kinds of questions that come up, such as stratification of data by grade of nucleus, etc.

But we will have all that information and right now, looking at early numbers, we will have further reduced effective phaco time by using this procedure compared with the same technology with coaxial.

And, as you know, we've shown that reduction of effective phaco time is one of the most important things you can do to make sure you have a clear cornea and good visual acuity the first day. But when I think of efficiency, I really think about what I have to do to get the outcome I want. And what I want is a happy patient on day one. And I think that I'm doing better now with bimanual than I was doing with coaxial before, and that's one of the reasons why I've stuck with it, and why I like it.

Lane: I think you're right. Dr. Packer had brought up the point that efficiency certainly means much more than time. And so I use time as just one barometer of efficiency.

Dr. Mackool's point was absolutely right about that. You find yourself chasing things a little bit more because the inflow coming from that needle tends to push pieces it away from your phaco tip much more than coaxial does.

And so your positioning of that second instrument is critical to avoid pushing that piece away and having it washing around the anterior chamber as you're trying to get a hold of it, regardless of your fluidics setting. So one tip for those that are starting this is to pay attention to that and determine how to position that second instrument. It takes a while to catch on and refine your technique.

Packer: I think that that is a critical point. Really, that stream of irrigation fluid is another instrument now in the eye. It's something we never had before. We now have control of inflow. And one of the things that I noticed right away was you get a nice piece right on your tip and the next thing you know it's shot over into the angle because you blew it away with your stream of irrigation.

So what I've tended to do is to have the aspiration and irrigation tip in different planes, or at least directed in different directions. And it's not always obvious from watching surgical video, because you don't have the stereopsis that you do through the microscope. But keeping the irrigating chopper further posterior and the aspirator in, say, the iris plane, is one technique for making sure that the stream doesn't knock the material off.

I also like to rotate my chopper horizontally when I get down to the epinucleus, so that that sharp element is no longer directed toward the capsule, but is horizontal. That way, I can actually direct the stream of fluid posteriorly to help inflate the capsule and keep it on-stretch. That facilitates trimming and rotating the epinucleus. You can actually use the phaco needle to rotate the epinucleus, or you can use the blunt end with irrigation fluid coming out, because you know that flow is keeping the capsule away.

Steinert: At the beginning, I would find that I always had at least one nuclear chip kind of plugged against the outflow, and it was very annoying to me. I'm working with a couple of the companies on changing from this end opening irrigant outflow on the chopper to going back to the side outflow, because I think that that will solve a lot of these issues.

I think personally, at least with my technique, that I need two instruments, not one. When I chop, I typically use my clawed chopper to break up the nuclear particles.

When I get down to my last particle and I'm in danger of the posterior capsule starting to come forward, I always switch with coaxial phaco to a second instrument, which is much more of a capsular-friendly spatula type instrument in order to manipulate the epinucleus. Everybody has a different way of approaching these challenges.

I think we're going to see a rapid evolution, just as we did in 1993 when Nagahara introduced phaco chop. I think we're going to see things kind of gel toward a more consistent approach and it will solve most of the issues you're bringing up.

Lane: Dr. Packer mentioned capsulorhexis. Dr. Steinert, do you want to just talk briefly about how you handle a capsulorhexis through those small incisions?

Steinert: Earlier we mentioned the oar lock and that is really a key issue with bimanual phaco. We are talking about very small incisions. And for those of us that work with residents that are learning cataract surgery, the very first thing you have to get through to them is the concept of an oar lock.

I've found with the very first rhexis forceps that we designed for this was that I was getting hung up at the incision by the outer leaf, should we say, and that would get hung up right at the Descemet's entry point where the rhexis was closest to the incision. But I think a couple of the companies' products I've had chance to use do a very good job at solving that problem.

Those products have better tapers and shorten the distance between where the grabbing teeth are and the end of that outer sleeve. As long as you keep that distance short, you don't get hung up.

The payoff is that you have better maintenance in the anterior chamber. And quite frankly, if I didn't need viscoelastic for the injector of the IOL, I don't think I would use it on most cases at all. You can use infusion capsulorhexis forceps now that will maintain your anterior chamber in an exquisite fashion.

Chang: I actually use a bent 25-gauge needle as an irrigating cystotome without any viscoelastic for the capsulotomy, and I think people can teach themselves to do that during routine coaxial phaco cases.

I would tense the globe with 1% lidocaine to facilitate a standard clear cornea keratome incision. The irrigating cystotome is introduced through a separate paracentesis. If there is a problem controlling the tear, you can always inject viscoelastic and finish the capsulorhexis with forceps through the standard incision.

There is an advantage to performing the capsulorhexis without viscoelastic when working through microincisions. One problem we haven't talked about is that after a forceps capsulorhexis, you usually have a chamber filled with viscoelastic and you have to be very cautious when hydrodissecting through a microincision.

Compared to a standard phaco incision, it won't decompress as quickly and as easily during hydrodissection and you may hyper inflate the anterior chamber in the process.

However, if you can complete the capsulorhexis with an irrigating cystotome without viscoelastic, you can insert the hydrodissection cannula through the paracentesis, and shallow the chamber by depressing the shaft slightly. Then you can safely inject the necessary amount of fluid to hydrodissect and spin the nucleus without suddenly over-expanding the chamber.

Lane: Let me play Devil's advocate here. At this point we don't have a lens approved in the United States that will fit through an incision that's as small as 1.5 mm or 1.2 mm in some of your cases. And so if that means we're back to the old days where we all remember when foldable lenses were en vogue, and we were doing phaco through a 3-mm or 3.2-mm incision and then opening it to 5.5 mm or 6 mm to put a PMMA lens in. Why should we be working on this? Why should we be doing small-incision bimanual phaco when we, indeed, have to open the wound up to put a lens in anyway?

Packer: While we don't have all the hard data in yet to say whether that's really the case or not, my feeling right now is that this is really a superior procedure. I want to continue doing it, long enough at least to find out for sure.

Mackool: The question really now begins to boil down to Are there intra-operative advantages?Ф Dr. Packer seems to believe that he's found some. Frankly, I have not yet been able to do so. It's slower, and I'd like to say that I could find some and I'm still trying to find some, but I can't.

Should we probe, should we push, should we look? Yes. But should we come right out and say to everybody this is the future of cataract surgery? I think we would be in danger of overstepping our knowledge at the present time if we did that.

Lane: There's been implications that you have to have certain types of machines that will be able to do this and you might not be able to do it with some of the older equipment. Can somebody address those issues? Can you, for example, do good bimanual microincision phaco using a Legacy instead of an Infiniti or instead of a WhiteStar?

Packer: Yes, it can be done with a Legacy. We've done it with the Infiniti, with the Sovereign, with the STAAR Sonic Wave, and with the Millennium. Any of these machines can be set up to perform safe and efficient microincision phaco.

It's clear you don't absolutely need any special capsulorhexis instrumentation to do this. We started with a bent needle. The first ones I did were that way, but I like starting with a pinch because I think there's better control.

So anyway, you should add a pair of capsulorhexis forceps. And then the main point is that you need to have a set of irrigating second instruments. Microsurgical Technology manufactures the Duet System, which includes a variety of front and side irrigating choppers and manipulators. ASICO makes side-irrigating choppers in a variety of styles.

And another thing that people might not think about is that you need to have a short sleeve on your phaco tip because there will be a lot of spray and outflow to wet your sleeve as you're operating.

Chang: The first thing is to get a bimanual I/A set and practice cortical cleanup with this setup for routine cases. It's important to get used to working through bimanual incisions, if you haven't already done that.

Next, don't try to do every step through a 1.2-mm incision. Because you need it for the IOL anyway, make and use your standard cataract incision for the capsulorhexis and hydrodissection. This allows you to evaluate and experiment with bimanual phaco instrumentation without the additional constraints of using a paracentesis for every step. As far as purchasing additional instruments, you mainly need to get an irrigating chopper.

As Dr. Packer said, MST provides many different interchangeable tips, and you can change the tips if you don't like the one you have. One place people might be tempted to cut corners is with using a Superblade to freehand the incision. You should obtain a metal keratome specifically sized for 1.2 mm.Otherwise, with free hand incisions, you never know from one case to the next how much the variability in chamber stability was from your incision size being a little larger or smaller.

Mackool: Dr. Lane, one word of caution to folks trying this early on: They shouldn't presume that because you make a one point something incision that it's perfectly sealed right away. These short incisions that have been deformed into a circle by a round metallic instrument can leak, and you may have to hydrate them and check them carefully.

Incisions need to be sealed at the end of the case. I would say to you that no matter what way you do them, bimanual or coaxial, you need to be sure they're sealed.

Lane: If I was a surgeon doing very successful coaxial phacoemulsification, would any of you tell me that I'm behind the learning curve in terms of what's going on now with bimanual phaco?

Chang: In my opinion, there is certainly no need to learn bimanual phaco now, because there are no clear advantages at this time. In terms of eventually being prepared to make the transition, I think it is extremely helpful to be proficient with phaco chop. We haven't talked about that, but I would venture that most people that regularly perform bimanual microincisional phaco are chopping, because it is the ideal technique for this.

In addition, if you are comfortable with chopping, then you already possess excellent bimanual skills, and the bimanual phaco learning curve will be much easier.

Lane: Where do you see this going in the future?

Mackool: In the final analysis, I think what will drive what we do is the best IOL. If the best multifocal IOL, for argument's sake, happens to require a two-point something incision, then you can bet there aren't going to be a lot of people doing two smaller incisions and then enlarging it.

The IOL is the big driver here. If we can get our patients to see better distance, near, and perhaps intermediate, with one IOL, if that IOL required a 5-mm incision today there would probably be a lot of those IOLs being inserted.

Steinert: Well, that's absolutely true. The IOL is going to be the final common pathway. But I strongly suspect that it won't be too long before we deal with 3-mm incision as archaic and just as unacceptable as a gaping extracap incision. So it's not wrong, it's not incumbent on anybody to get into this now, but if you don't want to be left behind you've got to at least, try bimanual I/A. And number two, really start getting into phaco chop.

Mackool: The fact that the bimanual procedure will require surgeons to master the phaco chop technique may turn out to be one of the greatest benefits of the bimanual procedure.