Bringing Refractive Surgery to a Whole New Level

American Academy of Ophthalmology 2011

Eric D. Donnenfeld, MD; Kerry D. Solomon, MD


November 02, 2011

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Advances in Femtosecond Laser Flaps

Eric D. Donnenfeld, MD: Hello. I am Eric Donnenfeld, Clinical Professor of Ophthalmology at New York University Medical Center, and a partner in Ophthalmic Consultants of Long Island. Welcome to Medscape Ophthalmology Insights.

Joining me today is Dr. Kerry Solomon, partner in Carolina Eye Care Physicians, Charleston, South Carolina, an Adjunct Professor of Ophthalmology, Storm Eye Institute, Medical University of South Carolina.

We are here today at the American Academy of Ophthalmology (AAO) meeting in Orlando to discuss femtosecond lasers in corneal refractive surgery. Today, I would like to talk to Kerry about advances in the femtosecond laser flaps and refractive incisions. What's new in femtosecond laser surgery?

Kerry D. Solomon, MD: Femtosecond laser surgery has brought an otherwise successful procedure in LASIK (laser-assisted in situ keratomileusis) eye surgery to a whole new level. It has brought a level of safeness and precision, and has allowed our results to improve beyond anyone's wildest dreams. For example, we can cut a more reliable and accurate thickness with a femtosecond laser compared with a microkeratome.

Dr. Donnenfeld: You did one of the largest studies ever on flaps after LASIK a number of years ago; it was really a landmark paper. Today, with femtosecond laser flaps, are they better than they were several years ago?

Dr. Solomon: No question. We are getting what we are aiming for, within 5 -- maybe 10 microns, at worst -- which is way better than we ever achieved with mechanical microkeratomes. When I aim to make a 110-micron flap in a patient, that is what I am going to get. That, in and of itself, adds a level of comfort and safety to the procedure.

Dr. Donnenfeld: It is not only about the thickness of the flap, there are other innovations with femtosecond laser flaps that are also important. Tell us a little bit about those other innovations.

Dr. Solomon: First, "beyond the thickness" means we can cut reliably thinner flaps. That also adds safety, because now we have more tissue to treat regardless of the thickness of the cornea. We have more room to treat so we can treat a larger group of patients safely and predictably, and since we know what our depth is, we are less likely to go too deep into the cornea. More recently, we can cut any shape or size of flap we want. We can cut a larger flap, or we can reduce the size to reduce the incidence of dry eye. We can cut an oval flap, which allows us to take advantage of astigmatism and yet minimize the size of the flap to reduce the likelihood of dry eyes. And recently, something we could never do with a microkeratome, we can actually change the angle of the edge of the flap. Studies have now shown (you have done some, I have done some) that cutting a vertical edge on a flap or even an inverted side cut has an advantage of reduced incidence of dry eyes, earlier visual stability, earlier visual recovery, and less likelihood of having to deal with nuances such as epithelial ingrowth, if an enhancement is required.

Fighter Pilot Vision

Dr. Donnenfeld: I have heard that LASIK is one of the safest procedures ever performed. Is LASIK performed in the Armed Forces and how does the Armed Forces feel about this technology?

Dr. Solomon: The Armed Forces would say it has been invaluable, that without it, their soldiers wouldn't be able to do what they do. Our military wouldn't have the success that it has had without the advent of excimer and femtosecond lasers. Femtosecond flaps have better adherence. The military has approved this procedure, NASA has approved it. In general, most people would feel from a safety, reliability, and predictability standpoint, femtosecond lasers have taken the most successful procedure in the world, and made it even more successful.

Dr. Donnenfeld: What I find amazing is that our patients today can have exactly the same laser procedure with the same flap and the same sculpting of the patient's cornea that a NASA astronaut or a Navy fighter pilot can have and that is what we are giving patients, that quality vision that you need for higher levels of vision.

Dr. Solomon: Quality vision is really one of the biggest keys because there are various levels of 20/20 vision. You can have a good quality 20/20, or a poor quality 20/20 vision. Contrast sensitivity plays a role, and higher order aberrations or irregularities play a role. We have done studies where we found that we could take the same laser, perform a customized treatment using a microkeratome, and compare those results with the same laser and the same customized treatment -- both groups received iris registration -- and the only difference was that a femtosecond laser was used to create the flaps in one group, and a microkeratome for the other group. The femtosecond group had better quality of vision, earlier visual recovery, and less induction of irregularities or higher order aberrations.

Dr. Donnenfeld: Let's translate this into English.

Dr. Solomon: Bottom line: the femtosecond cases had better quality of vision.

Grounding Expectations

Dr. Donnenfeld: If a patient comes in requesting laser surgery today, would you tell them that they can expect to see better, worse, or about the same as they do with their best glasses?

Dr. Solomon: Grounding expectations is probably the most important part of all of this, to make sure that patients have all of their goals and expectations aligned for successful outcomes, to have happy satisfied patients. The reality is, when we look at our data and also the military data for all patients having LASIK customized surgery with a femtosecond flap, we are finding a 20/20 rate of about 93% for all patients, and about a 55% rate of 20/15 vision. This is superb vision. But more importantly, we are treating things that glasses and contacts cannot treat. We are able to treat higher order aberrations. The quality of vision certainly can achieve that of glasses or contacts. I believe we often achieve that, and I hear every day from our patients, "this is better than I've ever seen before."

Dr. Donnenfeld: It is so exciting that most of our patients can see better than they do with their best glasses and that changes the patient's quality of life.

Femtosecond Laser Incisions: Manual Can't Compete

Dr. Donnenfeld: Let's move to a second topic. One of the most exciting topics at the AAO here in Orlando has been the advance in femtosecond laser cataract surgery. One of the major advances is the ability to make a limbal-relaxing or arcuate incision. What is a limbal-relaxing or arcuate incision and how does it affect vision? Why is this advance important?

Dr. Solomon: A limbal-relaxing incision is an incision in the peripheral cornea, typically just anterior to or central to the corneal vessels. The idea is to relax the tissue in that area to effect the treatment of astigmatism. Arcuate incisions are the same but they are more central to the cornea, typically at a 9 mm or even 10 mm optical zone size. I distinguish between a limbal-relaxing incision and an arcuate incision. With a limbal-relaxing incision, I typically use a diamond knife and performing a manual procedure, whereas with an arcuate incision, I use a femtosecond laser.

Dr. Donnenfeld: How does precision of the laser incision compare with the manual incision?

Dr. Solomon: The results are early. With a manual incision, I estimate or take an ultrasonic measurement of the corneal thickness. I manually set a blade, allow that blade to seat, and estimate as well as possible the cord length of that incision. But there is variability with the depth because different blades, even if you seat them properly, will penetrate deeper in different areas. Many of us do not even seat the blade properly, and estimations of the cord length are just that - estimations. With an arcuate incision by a femtosecond laser, we are using real time optical coherence tomography measurements, and setting the depth to exactly what we want. In my case, I use your nomogram, reducing it by a third. Setting it at 80% depth, I know I am getting exactly what I want because it's real time, my depth is uniform, and my arc length is exactly what I want. There is no way, in my experience, that a manual incision could compete with that.

Another advantage of the femtosecond-created arcuate incision is using it to titrate astigmatism, if necessary, postoperatively in the office. By not opening the incision at the time of surgery or not opening all of it, I can adjust it or open the incision in the office days to weeks to months after the surgery.

Moving Toward Refractive Cataract Surgery

Dr. Donnenfeld: What is also very exciting about femtosecond laser arcuate incisions is that you have the digital precision of a laser, and most ophthalmologists don't actually make these incisions. For the first time, it gives every ophthalmologist the ability to treat astigmatism to improve refractive results, and their results with even the earliest novice surgeon would be as good as the most advanced surgeon like yourself, because of the digital precision of the laser. We have essentially taken astigmatism management from an art form to a science.

Dr. Solomon: If you think about the prevalence of astigmatism, data by Warren Hill, for example, suggest that approximately 72% of patients will have treatable astigmatism of half a diopter or more, that can and should be addressed at the time of cataract surgery. That is 7 of every 10 patients, more than 1 out of every 2, will have astigmatism that can and should be addressed if we want to give our patients the best quality of vision after their cataract- or lens-related procedure.

Dr. Donnenfeld: The take-home message that has been presented at this meeting is that femtosecond laser cataract surgery increases the likelihood that our patients are going to be able to see better and possibly without glasses.

Dr. Solomon: No question. It is finally going to allow us to move to the next step. Besides just talking the talk, we are going to walk the walk. When we talk about refractive cataract surgery, femtosecond lasers are going to get us there.

Dr. Donnenfeld: I would like to thank you for joining us here today. This is Eric Donnenfeld with Kerry Solomon for Medscape Ophthalmology Insights.