Femtosecond laser market expands as new devices debut

Two new femtosecond lasers are now approved for use in the United States. Experts explain the differences in technology behind the lasers.

A large percentage of LASIK procedures are now performed using femtosecond laser technology for flap creation, and two newer femtosecond lasers have recently entered the U.S. market. With so much interest in the technology, Ocular Surgery News spoke to experts familiar with each laser to learn their similarities and differences.

Differences among the lasers include their firing speeds and the characteristics of the bubble layer formed by the intrastromal laser bursts, experts said.

IntraLase is the most established femtosecond laser manufacturer in the American market. According to the company, a quarter of all LASIK procedures in the United States are now performed using the IntraLase laser. The Femtec laser from 20/10 Perfect Vision received 510(k) approval from the Food and Drug Administration for use as a laser microkeratome in 2004, and the DaVinci laser from Ziemer Ophthalmics received FDA approval this March.

Now U.S. surgeons have three femtosecond laser devices from which to choose for LASIK flap creation.

“You’ve got a lot of companies interested in this technology,” said Perry S. Binder, MD. “I think it’s a great thing for ophthalmology that other companies are getting involved.”

IntraLase

Dr. Binder, the co-medical director at IntraLase, spoke to OSN about the IntraLase laser, which has gone through several iterations as the speed of its laser increased from 10 kHz to 60 kHz.

“As the speed gets faster, the separation between bubbles and energy can be decreased. As bubble separation and energy decrease, the smoothness of the dissection and ease of the dissection are improved,” Dr. Binder said. “The original time it took to make a 9-mm flap was 97 seconds. One can now make a 9-mm flap in 18 seconds.”

Dr. Binder and colleagues performed a clinical study comparing the stromal bed after IntraLase flap creation vs. the stromal bed after microkeratome flap creation. Three masked observers and a computerized quantitative surface analysis determined that the IntraLase stromal bed was significantly smoother than that produced by the microkeratome, he said.

“In terms of bubbles, the advantage of the 60 kHz laser is that it’s now going so fast, it gets ahead of the opaque bubble layer (OBL),” Dr. Binder said. “The OBL is becoming less of a significant slow-down process.”

The time needed to wait for the OBL to dissipate can be from seconds to as long as 5 to 10 minutes, Dr. Binder said. He said this delay can be turned to an advantage by using the OBL during this time as a means for measuring the flap thickness.

“But with the 60 Hz laser,” he said, “the bubbles are present for such a short duration in most cases that there is hardly time to obtain an ultrasound reading.”

Some surgeons are not concerned by the OBL, Dr. Binder said, and they lift the flap and treat while the OBL is still in place. He prefers to wait for it to dissipate. He said other surgeons have reported success with either method without the need to alter their nomograms. One concern, he said, is whether an eye tracker can be used while the OBL is in place in the stroma. He said this has not been a problem with the WaveLight Allegretto Wave or the Visx S4 lasers in his experience.

Dr. Binder said he is still unsure why the OBL occurs. But he said the bubble layer has become a less significant issue with the IntraLase Pocket Software, introduced in 2003, which allows gasses to go into a pocket by the hinge, and with the lower energy settings with the 60 Hz laser “it is almost a non-issue.”

Femtec

The Femtec femtosecond laser is approved in Europe, the United States and Korea for “intracorneal and corneal cuts,” which includes not only LASIK flap preparation but also lamellar and penetrating keratoplasty and tunnel preparation for intrastromal corneal ring placement, according to 20/10 Perfect Vision.

Mike P. Holzer

Since approval, the laser has been used in “hundreds of procedures” according to Mark Tomalla, MD. Dr. Tomalla and Mike P. Holzer, MD, told OSN about their experiences with the Femtec laser in e-mail interviews.

“The laser offers a patented interface that is adapted to the natural corneal curvature and therefore fits well on the patient’s eye,” Dr. Holzer said.

The spherical interface requires only minimal applanation of the eye, Dr. Tomalla said. “The cornea retains a near-natural curvature, resulting in lower increase of IOP and keeping corneal deformation to a minimum,” he said.

The laser uses a periphery-to-center spiral pattern approach, creating curved cuts that follow the stromal lamellae, Dr. Tomalla said. This contains the OBL within the periphery of the cut.

Dr. Tomalla said this containment allows a surgeon, depending on his or her preference, to proceed directly to the excimer procedure after a short time of waiting for the bubbles to dissipate. Dr. Holzer said he prefers waiting about 10 to 15 minutes for the bubbles to clear. He suggested that LASIK can be performed on another eye while the bubbles dissipate.

“It is easier to open the flap after the bubbles have escaped the cornea, and the surgeon sees the interface better,” Dr. Holzer said.

Dr. Tomalla said the Femtec offers the “broadest range of treatment options, with detailed computer control of all relevant parameters.” He said it takes 20 to 60 seconds to complete a flap.

Ziemer

The DaVinci femtosecond laser from Ziemer received FDA approval in March. Trials for its use in amblyopia are currently being conducted, according to company officials. The first creation of a corneal flap in a living human eye with the device was performed in April.

The laser, which operates in the megahertz range rather than kilohertz, allows for “smaller, lower-energy infrared laser pulses that dissect corneal tissue with unprecedented smoothness and precision,” according to the company.

Werner Barth, PhD, and Anton Wirthlin, PhD, both of whom are officials with Ziemer, spoke with OSN about the new device.

The DaVinci “is a much faster laser with the consequence that it generates much shorter pulses,” Dr. Wirthlin said. “These much shorter pulses ... create much smaller spots, focus the energy much more closely and, therefore, give rise to a different, improved cutting behavior of the laser.”

Dr. Wirthlin said this “precise cutting plane” is a result of the close proximity of the front lens of the laser to the eye. He said due to this shorter focal length, delivered through a larger aperture, the tissue above and below the plane are unaffected, and the OBL is not an issue.

“These bubbles are tiny little bubbles that don’t form an opaque layer in the interface. You just see tiny little spots that are separated by clear cornea,” Dr. Wirthlin said. “As soon as you lift the flap, these bubbles disappear instantaneously.”

Dr. Wirthlin added that the flap is cut “as if it were cut with a microkeratome” so there is no struggle to lift it.

Dr. Barth said flap creation time is between 45 and 50 seconds. He said it is “important to note that the time from vacuum on to vacuum off is only about 5 seconds longer, since interface foil, suction ring and tubing and protective covers are all assembled off the eye.” Once suction is applied, he said, cutting can begin immediately.

Dr. Wirthlin said that “more important for the practitioner is how the laser handles.” It is small, mobile and stable, he said, and designed to be taken from room to room or even from one facility to another.

“The fact that the laser is so small also means that you can move it right next to the excimer laser when you do LASIK,” Dr. Wirthlin said. “The surgeon ... has one workplace where he does the entire procedure, pretty much like he used to do with a microkeratome.”

For more information:

• Perry S. Binder, MD, can be reached at the GordonBinder Vision Institute, 8910 University Center Lane, Suite 800, San Diego, CA 92122; 858-455-6800; fax: 858-455-0244; e-mail: garrett23@aol.com. Dr. Binder is co-medical director at IntraLase and is a paid consultant to that company.
• Mark Tomalla, MD, can be reached at Eye Centre, Clinic for Refractive and Ophthalmic Surgery, Ev. u. Joh. Klinikum Niederrhein, Fahrner Str. 133-135, 47169 Duisburg, Germany; 49-203-5081711; fax: 49-203-5081713; e-mail: mark.tomalla@ejk.de; Web: www.augenklinik-duisburg.de.
• Mike P. Holzer, MD, can be reached at Department of Ophthalmology, University of Heidelberg, INF 400, 69120 Heidelberg, Germany; e-mail: mike.holzer@med.uni-heidelberg.de.
• Werner Barth, PhD, the vice president and chief sales and marketing officer for Ziemer Group, can be reached at Ziemer Group AG, Allmendstrasse 11, CH-2562 Port, Switzerland; 41-32-332-7070; fax: 41-32-332-7071; e-mail: werner.barth@ziemer-ophthalmics.com.
• Anton C. Wirthlin, PhD, the vice president of marketing for Ziemer Group, can be reached at Ziemer Group AG, Allmendstrasse 11, CH-2562 Port, Switzerland; +41-0-32-332-7052; e-mail: anton.wirthlin@ziemer-ophthalmics.com.

• Katrina Altersitz is an OSN Staff Writer who covers all aspects of ophthalmology.