Recent laboratory research findings by Steven E. Wilson, MD, director of corneal research at the Cleveland Clinic Foundation, may underscore what many surgeons have already surmised: Femtosecond laser technology is continuing to improve.
Introduced in 2002 by IntraLase Corp., this cornea flap creation device uses a rapidly fired pulse in the femtosecond (one quadrillionth of a second) range with a spot size of 3 micrometers. Computer software guides the laser beam to create overlapping spots, which result in a cut of the cornea at a depth determined by the surgeon. An excimer laser is then used to perform the rest of the LASIK procedure.
Why the Improvement?
In April 2005, the company introduced an upgraded model of the IntraLase, which increased the speed of the laser to 30 kilohertz.
According to Dr. Wilson, this has greatly improved performance over the earlier models, which were running first at 10 and then 15 kHz. “Last year, when comparing the first femtosecond model with a mechanical microkeratome to create flaps in rabbits, we found more proliferation of stromal cells following the laser cut and more inflammatory response with the femtosecond method,” Dr. Wilson pointed out. “However, we recently repeated those studies in the 30 kHz upgraded model and observed that while there is still a tendency for more inflammation and a stronger wound healing response with the femtosecond flap compared with the microkeratome flap, this difference is markedly decreased—observations that we have noticed in our clinical practice as well.”
Dr. Wilson added, “We continue to treat femtosecond laser patients with corticosteroids every hour (except during sleep) for the first day to help avoid diffuse lamellar keratitis (DLK), but I think that it is becoming less clear that this treatment approach is actually needed, and we are planning to slowly decrease this regimen.”
Dr. Wilson also found that it was much easier to lift the microkeratome flap than the femtosecond flap, which can be an issue in terms of subsequent enhancement. “However,” he noted, “I have never had to lift a femtosecond flap six months after surgery.”
He added that if patients are selected properly, there is no difference in flap complications between the two procedures.
Dr. Wilson, who has submitted this data on “wound healing with the femtosecond laser compared with the microkeratome flap” for publication, explained that much of the improvement offered by the 30 kHz upgrade can be attributed to the increased speed of the laser and refinement of energies delivered to the sidecut. With the latest model, the flap creation process from start to finish takes just under 30 seconds, on average.
Seducing the Skeptics
This technology improvement has caught the attention of an increasing number of surgeons, including those who did not embrace the femtosecond concept when it was first introduced. Richard L. Lindstrom, MD, managing partner of Minnesota Eye Consultants in Minneapolis, is one such surgeon.
“The early outcomes data with the femtosecond laser weren’t any better than the mechanical microkeratome, so I couldn’t make an argument to switch to femtosecond. And, quite frankly, I wasn’t that unhappy with the mechanical microkeratome.”
And while Dr. Lindstrom liked the idea of a reproducible flap—a claim made by the femtosecond manufacturer—he did not think the benefits outweighed the drawbacks, including higher costs and lower patient volume due to the time it took to perform the technique. “These were all issues that made me neutral on the subject, and lean toward remaining with the microkeratome,” he noted.
A second look. However, continued improvements in the technology prompt-ed Dr. Lindstrom to revisit his previous stance, and he recently placed a femto-second 30 kHz laser in his practice to compare flap creation to the Hansatome mechanical microkeratome. “I wanted to gather firsthand information to make the right decision whether to purchase this technology for TLC Vision [of which Dr. Lindstrom is the medical director],” he said. “Let’s face it: Everyone believes their own data.”
Dr. Lindstrom and his colleague Elizabeth A. Davis, MD, a partner at Minnesota Eye Consultants, have found that the femtosecond laser achieves a significantly higher number of 20/20 vision results or better, one day, one week, one month and three months following the procedure, with a higher percentage of patients attaining 20/16 vision. In addition, there is a lower incidence of bad flaps, corneal abrasion, DLK and corneal epithelial ingrowth. “We were also impressed that our flap thicknesses were more reproducible with the femtosecond, and that we could achieve perfect centration of the flap with every single procedure,” he added. “We also found that the Intra-Lase technology married well with our Visx lasers, and the process did not slow down our caseload.”
In light of these findings, Dr. Lindstrom has dramatically changed his position on femtosecond technology, and he shared this new view at the October Academy meeting in Chicago—much to the surprise of many of his colleagues. “In six months, if it turns out that patient outcomes are improving, with better vision earlier and a meaningfully higher percentage of patients with 20/20 levels or better, combined with a significant reduction in complication rates, we will be transitioning more TLC centers to the femtosecond technology. Most impressive to me is the centration issue, and the fact that we can do thinner flaps—100 to 110 microns.”
Femtosecond firsters. This “conversion” is not a surprise to surgeons such as Perry S. Binder, MD, cofounder of the Gordon, Binder and Weiss Vision Institute in San Diego, who uses the femtosecond exclusively. He noted that the 30 kHz upgrade has resulted in a faster procedure time, tighter spot placement and lower energy. “We are not seeing all the side effects that were occurring with the extra energy,” Dr. Binder said.
According to IntraLase Corp., the tighter spot placements result in superior dissection quality and corneal interface, and facilitate flap elevation. The lower energy output diminishes the potential for postoperative inflammatory response. In addition, the company has expanded its therapeutic applications for the femtosecond laser to include anterior lamellar keratoplasties and posterior corneal transplants. While Dr. Binder and his partners still perform PRK, he said, “We haven’t touched a microkeratome in three years.”
H. Dwight Cavanagh, MD, PhD, vice chairman of ophthalmology at the University of Texas Southwestern Medical Center in Dallas, is another surgeon who uses femtosecond technology exclusively in his practice. He said that while complications with a mechanical blade cut were rare, he has not seen any IntraLase flap complications.
As Always, Cost Is an Issue
Drs. Lindstrom and Cavanagh agree that the one major drawback to IntraLase is its cost.
“There is always a worm in every apple, and purchasing a $400,000 laser will inevitably add more cost to the procedure,” Dr. Cavanagh said. “Yet any time you improve technology you increase the cost of it, but I believe you achieve an increased safety net as well.”
Dr. Lindstrom was also initially concerned with the increase in cost. Yet his practice was able to raise the price $400 in each eye, and 65 percent to 70 percent of his patients continue to select the femtosecond for their surgeries despite this cost.
“However,” he noted. “I believe that this financial barrier is very real, and may prohibit those with low-volume refractive surgery practices from being able to offer this technology. And it will never be the dominant technology in the discount eye center.”
Tracking the Trend
Dr. Wilson pointed out that as femtosecond technology continues to improve, there may be a shift in practice patterns concerning flap creation. Currently, he incorporates both femtosecond laser technology and mechanical microkeratome into his practice. “There are three groups of patients whom I believe can benefit from the IntraLase—those with corneas that are too steep, too flat or insufficiently thick to perform a correction with the microkeratome. IntraLase is also good for epithelial basement membrane dystrophy,” he said.
Moderation, for now. While Dr. Wilson views IntraLase as an essential tool for a refractive surgical practice, he said, “It is not necessary for every patient, and we need to think about cost and subsequent enhancement issues. I think I have found a happy medium where it fits in my practice alongside the microkeratome.”
Drs. Cavanagh and Wilson have no related financial interests. Dr. Lindstrom’s financial interests include IntraLase, AMO and Bausch & Lomb. Dr. Binder’s financial interests include IntraLase.