Femtosecond laser refractive techniques steadily gaining momentum

Burgeoning innovations enable flapless intrastromal vision correction and lamellar extraction.

Daniel S. Durrie

For more than a decade, excimer laser-generated tissue ablation has been the gold standard for safe, effective and precise corneal refractive surgery for myopia, hyperopia and, to some extent, presbyopia.

More recently, the introduction of femtosecond lasers has enabled surgeons to cut customized LASIK flaps that some believe are safer and less prone to postoperative complications than conventional microkeratome-created flaps.

The newest femtosecond laser techniques offer smaller flaps and flapless intrastromal correction. One technique offers femtosecond laser-only refractive correction without an excimer laser.

Ongoing developments in femtosecond laser technology herald an era of fierce competition among laser manufacturers, Daniel S. Durrie, MD, OSN Refractive Surgery Section Editor, told Ocular Surgery News.

“I think that we are going into a whole era of what I call the femtosecond face-off,” Dr. Durrie said. “What you’re going to see is a lot of good things happening for us in the market because innovation will happen. Competition is always good. … I think [companies] are putting good energies into a field that I think is really going to help patients and improve safety and accuracy as we move along.”

Advanced Medical Optics (now Abbott Medical Optics) introduced the IntraLase femtosecond laser and continues to play a major part in the femtosecond laser market worldwide. In addition, Carl Zeiss Meditec, Technolas Perfect Vision, Ziemer and Alcon/WaveLight have femtosecond lasers either on the market or entering it.

However, amid the rise of femtosecond technology, nomograms and eye tracking continue to enhance and individualize excimer laser ablation, OSN Chief Medical Editor Richard L. Lindstrom, MD, said.

“In excimer, we are seeing incremental advances, including better algorithms to adjust for spherical aberration, and better trackers including torsional tracking,” Dr. Lindstrom said.

Femtosecond-only vision correction

In early April, Carl Zeiss Meditec announced that ReLEx, its proprietary brand of femtosecond laser-based vision correction procedures performed with the VisuMax femtosecond laser, is available outside the U.S. Procedures under the ReLEx umbrella include Femtosecond Lamellar Extraction (FLEx) and Small Incision Lamellar Extraction (SMILE), which involve precise tissue cutting rather than tissue ablation.

Surgeons can also use the VisuMax platform to perform lamellar keratoplasty, penetrating keratoplasty and flap cutting, according to a Zeiss press release.

Richard L. Lindstrom

“It’s an interesting option but I see no evidence it is superior to LASIK when done with the flap lift technique,” Dr. Lindstrom said. “On the contrary, visual acuity outcomes are not as good. If it can be done without lifting a flap, it might be less invasive. Still, it’s an interesting newer approach and time will tell.”

However, femtosecond intrastromal procedures show potential in the correction of presbyopia, he said.

“In femtosecond, I am excited about intrastromal incisional [techniques] for all refractive errors, especially presbyopia,” he said.

Dr. Lindstrom noted that, despite femtosecond techniques being less invasive than current methods, excimer laser approaches continue to yield superior correction of high refractive errors.

Flapless intrastromal correction

IntraCor, Technolas Perfect Vision’s flapless intrastromal correction method, “is bringing us back to where we first started with IntraLase in the year 2000,” Dr. Durrie said.

The new IntraCor technique corrects vision by cutting intrastromal fibers and altering the biomechanical properties of the cornea, somewhat like radial keratotomy, he said.

“It doesn’t remove the epithelium, it doesn’t cause any discomfort and vision recovery would be quite rapid. This is a biomechanical destabilization procedure, meaning that we are cutting the cornea, then it changes shape,” Dr. Durrie said. “In those kinds of procedures we need to see if there are any long-term effects, like radial keratotomy, which was a biomechanical destabilization and had good results for 3 years, then problems popped up after that.”

Although further study is needed, preliminary results have been promising, Dr. Durrie said.

“What is the variation from patient to patient? Does everybody respond the same or is there a significant difference between the patients? I think it’s something that should be tried, should be studied, and I think we’re starting to see … early data that’s encouraging.”

Dr. Lindstrom also pointed to the potential of femtosecond flapless intrastromal surgery.

“It looks like femtosecond laser incisional surgery in a variety of patterns can correct presbyopia, myopia, hyperopia and astigmatism,” he said.

Push for further excimer laser innovation

As femtosecond laser surgery evolves, there is still room for continued innovation in excimer laser technology, Dr. Durrie said.

“We’ve come a long way and very fast in the first 15 years of development of the excimer laser and we’ve done remarkable things, but let’s not stop here,” he said.

Ongoing study should focus on customized ablation profiles involving less tissue removal than existing techniques, Dr. Durrie said. He noted that no clinical trials for excimer lasers have been conducted in the U.S. for more than 4 years.

“Alcon/WaveLight recently started a topography-guided study, which could be very exciting,” he said.

“A lot of the companies … have programs going on outside the [U.S.] but we need to have them spend the time, effort and money to do a clinical trial on their next generation of technology,” he said.

Future excimer laser trials should focus on further refining a proven technology, Dr. Durrie said. He is encouraged by his own studies with good patient selection, in which he has achieved 20/20 visual acuity for 100% of patients in a few recent studies.

“I’m not saying there’s anything wrong with what we have now, but that doesn’t need to mean you stop trying to innovate,” he said. “We may find out that we’ve reached the top of the S-curve and where do we go from there?” – by Matt Hasson

• Daniel S. Durrie, MD, can be reached at 5520 College Blvd., Suite 200, Overland Park, KS 66211; 913-491-3330; fax: 913-491-9650; e-mail: ddurrie@durrievision.com.
• Richard L. Lindstrom, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 106, Minneapolis, MN 55404; 612-813-3600; fax: 612-813-3660; e-mail: rllindstrom@mneye.com.