Femtosecond Laser: Changing the Face of Cataract Surgery

Roger F. Steinert, MD; Stephen S. Lane, MD


November 21, 2012

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Talking Femtolaser Technology

Roger F. Steinert, MD: Hello. I am Dr. Roger Steinert, Director of the Gavin Herbert Eye Institute and Professor and Chair of Ophthalmology at the University of California, Irvine. Welcome to Medscape Ophthalmology Insights, coming from the American Academy of Ophthalmology (AAO) meeting in Chicago.

Joining me today is Dr. Stephen Lane. Dr. Lane is Adjunct Professor at the University of Minnesota. Welcome, Steve, and thanks for taking time from your busy Academy schedule.

The subject that we want to discuss today is the latest in femtosecond laser technology. You probably have the most experience of anyone in the United States. We are eager to hear how it is working out in your practice.

Stephen S. Lane, MD: Femtosecond laser cataract surgery is a very exciting aspect of what we do in ophthalmology now. It's one of those buzzwords that people are talking about in terms of its potential capability and how it's changing the face of cataract surgery. Despite its relative infancy, the femtosecond laser has had a major impact on cataract surgery in the United States, with approximately 120 units from various manufacturers available out there. We are starting to see innovations with this technology that have made it even better since its introduction a year ago. The upgrades and innovations that have occurred within a relatively short period of time are simply amazing.

Another (Tremendous) Tool

The femtosecond laser is certainly very common to all of us in our use in corneal refractive surgery, and we use it to a great extent, but the changes that took place and the innovations that took place with those femtosecond lasers [for corneal refractive surgery] took a year, sometimes 2 years, to develop. It was fairly slow in coming. In contrast, the LenSx® laser (Alcon; Fort Worth, Texas), which is the one I'm most familiar with and the one that I use the most [for cataract surgery], has had essentially 6 upgrades within the year that are serious upgrades -- not something that's just simply bells and whistles, but true upgrades to the technology.

The femtosecond laser is another tool to help us better determine what our postoperative results will be for our patients. To call it the Holy Grail, to say that this simple yet very sophisticated laser is going to give us better clinical results simply by its very nature, is really folly. It's a tremendous tool with tremendous precision; but, overall, the best way to think about it is as one tool of many in our toolbox to help us get better results. It's certainly expensive, but it's also innovative and gives us better results. That combination -- this tremendous but expensive technology -- is what worries people.

The 4 major parts of cataract surgery with the greatest variability are incisions, capsulorrhexis, the creation of arcuate incisions, and the softening of the lens. These 4 variables can be standardized. I can put my parameters onto a key and send it to you across the country, and you can plug it into your laser and have exactly the same settings and do it exactly the way that I do. If you wanted to, you could potentially get the same results that I do with those variables. That's exciting, because as we figure this out together, it becomes very interchangeable.

You have tremendous precision in the type, length, and depth of incisions. Capsulorrhexis, which is a tricky part of the procedure for many, can be standardized in terms of its size, location, and shape. The lens softening can reduce the amount of energy inside the eye and make the removal of the lens easier. Of course, the use of arcuate incisions is a good way of standardizing the incision. So, we can take 4 of the most difficult parts of the procedure, standardize them, and make them easier, more precise, and probably safer, which will lead to better clinical results.

Precision Incisions

Dr. Steinert: One thing we have wondered is whether the ability to make controlled, repeatable incisions leads to better self-sealing of the incisions and may lower our already low risk for endophthalmitis. Have you had a chance yet to start changing the shape or pattern of your incisions to try to influence that?

Dr. Lane: Yes, I have. I have tried a number of different patterns -- 2-step incisions, single-plane incisions -- and right now the incision that I am using is a 3-plane incision. I originally thought that because of the configuration of the wounds made with a metal or diamond knife, that a 3-plane incision made the most sense -- with the initial incision fairly shallow, and then a longer tunnel and then a little dimple down like we used to make with a knife. I have found that in terms of water tightness, a 3-plane incision where the original tangential incision is about 60% deep, with a little bit of a shorter tunnel, and a third entry point, really adds to the stability of the wound. It's like the old Langerman incision that used to be made by hand, maybe not quite as deep. But that was a tremendously well self-sealing incision, and I'm getting very stable results.

Although I can't say that I never hydrate (because I certainly do hydrate the primary incision), it's certainly not something that I have to do every single time as I did with most of the manual incisions that I made before. That might be because I'm not inside the eye as long as I was before, because so many of the steps have already been done. I don't have to be in there with a forceps to make the capsulorrhexis, or take as long to do the phaco, because it's already broken up into quadrants. Less chopping and fewer manipulations need to be done. The back-and-forth and in-and-out and torsional movements within the wound are reduced simply because it's been broken up and it's ready to go in and remove.

Dr. Steinert: It's going to be interesting to see how that all of this plays out with the incisions. You talked about the 3-plane incision, which a lot of us have thought we were doing, and yet Perry Binder and others have done optical coherence tomography (OCT) studies on the diamond knife, and in fact it isn't a 3-plane incision after all. You think you are dimpling down, but you are actually arching, whereas when you look at the OCT and the laser, it is distinctly 3 planes. It's not going to be the same incision [that you made manually].

Astigmatic Keratotomy: Laser vs Diamond Knife

With astigmatic keratotomy (AK), what can this technology do better than with a diamond knife? Two things that have come up are pure intrastromal incisions for smaller corrections and the idea of titrating, because the femtosecond laser typically leaves little tissue bridges so that you could do the full-thickness penetrating astigmatic incision out almost to the limbus if you wanted to, but then not necessarily open at all. At the slit lamp, postoperatively, if you want more of an effect, you can tweak it a little bit and open up a bit more. Have you used either of those approaches?

Dr. Lane: Yes, more the latter than the former. When you think about combining it with intraoperative aberrometry, it is exciting, because you can do a measurement of the astigmatism when the arcuate [incision] has been made and determine on the table whether you want to open up all of it or part of it, or open up part of it and do a reading, and then based on that reading, open up more or leave it for another time. That is basically what we do when we titrate it in the clinic. We put the patient in front of the topographer or keratometer, measure, and say, "Okay, I'm going to open this halfway." Then you take them back to see the effect of that, and you may or may not do more.

I am getting to the point where I am doing more AK than I need to do to give me the flexibility of opening it up if I need to or not. We are all developing our own nomograms for how much of an effect an unopened incision (or an intrastromal incision) is taking up. But it's the titratability that you talked about that is possible with a full-thickness penetrating type of AK, as opposed to an intrastromal incision, that will give us the titratability, and it is for real. It's as for real as going back months later and reopening the same incision if you might not get enough of an effect at that time.

Making a Better Capsulorrhexis

Dr. Steinert: With respect to the anterior capsulotomy, for the past year there has been talk about tags, incomplete cuts, and how you deal with that. Recently the maker of LenSx, the device you use, has introduced a potential solution for their system. Can you tell us about that?

Dr. Lane: The difficulty that we have had with the LenSx laser in the past was with the occasional capsulorrhexis; there would be little tags which were discontinuities in the pattern that was made. It was essentially a small adhesion between the free portion and the outer part of the capsulorrhexis, so that it had to be pulled toward the middle where it would tease apart. But there was a connection there that many people worried could lead to a radial extension that could cause significant problems during surgery. All along, the desire has been to make a perfectly pristine, complete capsulorrhexis that did not have any adhesions, and LenSx solved that problem by using a hydrogel contact lens that fits in an interface that was very similar to what we have been using, with mild modifications. The skirt around it is a bit softer, so it molds to the eye. By using a hydrogel contact lens on the inner aspect, the contact is now between the contact lens and the surface of the cornea. That does several things. It provides a liquid interface without any liquid because of the high water content of the contact lens.

Second, we're able to gain apposition to the cornea and induce suction, which is necessary to hold the eye still. But we can do it at a much lower pressure, so the patient can continue to visualize the fixation target during the procedure. The work that has been done suggests that it's about 16 mm Hg higher than the patient's resting intraocular pressure. A patient with intraocular pressure of 20 mm Hg theoretically would end up with a pressure of 36 mm Hg when this was fully suctioned. This isn't a very significant pressure, but it might be helpful in patients who have glaucoma in whom you are concerned about raising the intraocular pressure too much. It also allows the patient to fixate.

The ability of the contact lens to create a docking process, where the docking is flat, allows us to better position the incisions; and during the capsulorrhexis itself, because there are no wrinkles in the cornea (because of this interface), we can make a perfect capsulorrhexis with very pristine edges that are virtually complete in 100% of patients. We can now literally reach in, grab the center of the capsulorrhexis, and pull it out, or even use our phaco tip and aspirate the whole disc to start the procedure. The capsulorrhexis is more pristine and stronger. Several studies have shown that that capsulorrhexis is stronger than those made manually. These techniques will be valuable in helping us improve results.

The Safety Advantage

Dr. Steinert: We haven't eliminated ultrasound yet. Are you finding any effect on your ultrasound and phaco times?

Dr. Lane: Yes, very significantly. The amount of energy that we are introducing into the eye is much less than what is used with the manual breakup and removal of the lens. A fair amount of energy is dispelled as we make grooves and do chops, especially in harder lenses. Much of this work is being done by the laser now. It's like a scored candy bar that you can snap very easily and use much less energy for removal.

There is a tremendous safety advantage as well, especially in softer lenses. Those are challenging. They are soft enough that you can't break them up. The femtosecond laser softens them so that you can do the entire cataract procedure on vacuum alone without introducing any ultrasound whatsoever, which we haven't been able to do before. The added safety margin of not having to introduce any phaco energy into the eye is significant. It's not just that the hard lenses are easier, but the soft ones have proven to be a much easier task than before.

Dr. Steinert: It's very exciting to see how far this field has gone in the shortest amount of time of any major new technology ever. People lose sight of the fact that Kelman started phaco in 1967, and it really wasn't being adopted (except by a few cutting-edge surgeons) until the early-to-mid 1980s, and this timeframe is vastly different.

Thank you for sharing all of those insights. I'm Dr. Roger Steinert with Dr. Steve Lane for Medscape Ophthalmology.