Flap-cutting Technologies Provide Choices

Laser microkeratomes are gaining ground, but one surgeon says that mechanicals still deliver.

BY RENÉ LUTHE, SENIOR ASSOCIATE EDITOR

With femtosecond laser microkeratomes cementing their status as "the next big thing" in refractive surgery, some surgeons may wonder about the future of the tried-and-true mechanical microkeratome. After all, the IntraLase FS laser (Advanced Medical Optics [AMO], Santa Ana, Calif.), now in its fourth generation with a 60 kHz pulse rate, has shown continued growth. According to AMO, procedure sales for the third quarter of 2007 were $12.3 million, an 81% increase from the year-ago quarter; revenues from the second quarter of 2007 showed a 98% increase from that period in 2006.

And more femtosecond lasers are on the way: Carl Zeiss Meditec (Dublin, Calif.) received FDA approval for its own version, the VisuMax Femtosecond Laser workstation, last year and Ziemer Ophthalmic Systems AG (Port, Switzerland) currently has a model in clinical trials here, the Femto LDV. Should refractive surgeons accept the inevitable, put their mechanical microkeratome in storage and shell out the money for a femtosecond of their own?

Mitchell A. Jackson, M.D., of Lake Villa, Ill., has extensive experience with both types of devices. In his private practice, he uses both the Hansatome and the Zyoptix XP (both Bausch & Lomb, Rochester, N.Y.); at a LASIK Plus corporate practice, he uses the IntraLase. According to Dr. Jackson, the answer to that question is: It depends. For certain eyes, a femtosecond laser offers definite advantages. Here are his guidelines to choosing a laser or mechanical microkeratome.

Femto and the Seven Dwarves

Dr. Jackson says he finds the visual outcomes for mechanical microkeratomes and femtosecond lasers to be comparable, but adds that in specific conditions, the IntraLase does offer an advantage. "We call them the Seven Dwarves," he explains. "In eyes that are flatter (K readings less than 40), steeper (K readings greater than 47), corneas that are thinner (pachymetry readings less than 50 μm) or smaller (corneal diameter of less than 11 mm), eyes that are deep-set, patients who tend to squeeze their eyes and tighter eyelid anatomy, I find the IntraLase is a lot easier. Most of the time, with the IntraLase, I don't use a lid speculum when I create the flap, so patients typically don't feel suction as much — so squeezers squeeze less because they feel less during flap creation. With a really deep-set or tight-lidded patient, it's much easier to get the cone in there. If you don't use a lid speculum with a mechanical, it's still tough, and it's a bigger piece of machinery going into the eye. And if the eyes are too steep, you have a higher risk for buttonholes with the mechanical, less with the IntraLase."

In addition, the femtosecond laser helps the surgeon avoid a free flap in a flat eye. And for eyes with thin corneas, "you want to have a tighter standard deviation controlling how thick the flap is to avoid having to do a PRK," Dr. Jackson says. "So the IntraLase has the advantage."

He notes that approximately 20% to 25% of the patients he encounters fall into one of the seven categories for which the IntraLase is the better option. For the other cases, he uses a mechanical microkeratome.

Many of the problems that plagued the earlier generations of the IntraLase, Dr. Jackson reports, are now largely nonexistent. "I used the first-generation IntraLase (15 kz), when it came out in about 2002," Dr. Jackson says. "The new IntraLase is leaps and bounds ahead. I saw all that DLK [diffuse lamellar keratitis] and transient-light photophobia that they talked about with the first generation, but I rarely see any of that now. And the OBL [outer bubble layer] problem is not an issue," he continued, referring to the gas bubbles that broke through the flap in previous generations of the laser, interfering with the beam so that the surgeon could not lift the flap. "I don't even have to wait, I just lift right away."

Is Mechanical Still Modern?

Despite all the buzz in recent years for femtosecond technology, Dr. Jackson believes there is still "a huge place" for mechanical microkeratomes in today's market. "They have longevity, they have the history already," he points out. "Surgeons have great experience with mechanicals." That longer history may make them more favorable. In the ultimate expression of confidence, he says that when he underwent refractive surgery, he chose a mechanical microkeratome for flap creation. "I could have waited for the femto; I didn't," Dr. Jackson says. "If you have a good surgeon, you are going to be fine."

Further, mechanical microkeratomes are evolving to provide better performance. The new XP, he says, offers suction that is equivalent for both the standard and smaller ring. "The standard deviation on the flaps are much tighter than they used to be," he adds. A 2007 study conducted on six eyes by Sarayba et al., found that although the IntraLase created a smoother LASIK stromal bed than the Zyoptix XP, the Zyoptix produced "smooth, good-quality, compact stromal beds qualitatively and quantitatively."¹

Similarly, Patel et al. recently reported in a comparison of the IntraLase with the Hansatome that the method of flap creation did not affect visual outcomes 6 months after LASIK surgery.² (The weight of other studies proves inconclusive.)

Dr. Jackson notes that in his experience, he has not seen a significant difference in visual outcomes between the IntraLase and mechanical microkeratomes. "I still think on thinner corneas, it's probably a little more of an advantage to use IntraLase," he says. "But there is a place for both technologies, in my opinion."

Marketing Considerations

In addition to surgical considerations when choosing between the two technologies, there are financial considerations as well. For instance, current market considerations may give mechanical microkeratomes the edge among practitioners — for now. "It's already a tight market," Dr. Jackson says. "Our volumes were fairly flat last year. It's hard to spend money on the femto right now, and that's the last thing surgeons are going to do if they have good results with the mechanical. Nobody wants to pay the extra $300 per eye."

In the world of corporate medicine, he points out, the laser center can negotiate a favorable financial rate with the device manufacturer, particularly if it is part of chain. "In the corporate world, they make the deals and you get to use the toys," is how Dr. Jackson puts it. Private practices, however, are forced to be more frugal. "You have to consider that, while it would be nice to have the IntraLase, you have to justify the expense," he says.

For practices that do choose to invest in a femtosecond laser, Dr. Jackson says having a different fee schedule for it can help recoup costs. For example, a practice could have one, higher fee schedule, but do more procedures on the mechanical microkeratome so that margins are greater. "The problem is that with a lot of IntraLase lease deals, people have minimums they have to do," he says. "So the decision depends on your volume." At the LASIK Plus office, he reports that they do an upgraded fee. "We say, 'If you want bladeless [LASIK] here are the reasons why it might be an advantage in your case.' We usually convince patients."

New entries to the femtosecond market, such as the Femto LDV and the VisuMax, should soon make femtosecond lasers more cost competitive.

Room for Two

Dr. Jackson reiterates that mechanical microkeratomes are still a very relevant tool to today's refractive surgeons. "I don't think it's a standard of care to use the IntraLase," he says. "I think it is another technology. There's a place for both, in my opinion." OM

Dr. Jackson is a consultant for Bausch & Lomb.

References

1. Sarayba MA, Ignacio TS, Tran DB, Binder PS. A 60 kHz IntraLase femtosecond laser creates a smoother LASIK stromal bed surface compared to a Zyoptix XP mechanical microkeratome in human donor eyes. J Refract Surg. 2007; 23:331-337.
2. Patel SV, Maguire LJ, McLaren JW, Hodge DO, Bourne WM. Femtosecond laser versus mechanical microkeratome for LASIK: a randomized controlled study. Ophthalmology. 2007; 114:1482-1490. Epub 2007 Mar 13.