Femtosecond laser procedure for spherical myopia yields solid safety results

Take Home:

A femtosecond laser platform (VisuMax, Carl Zeiss Meditec) showed excellent safety results for spherical myopia correction with promising effectiveness outcomes 3 months postoperatively.

San Francisco-Initial FDA clinical trial outcomes of a femtosecond laser system (VisuMax, Carl Zeiss Meditec) to correct spherical myopia showed solid clinical and safety results.

That was the overall assessment by Jon Dishler, MD, Dishler Laser Institute, Denver, and medical monitor and one of five principal investigators for the VisuMax Myopia Study.

Advance for myopic correction

“My overall impression is that this could represent a significant advance in the surgical correction of nearsightedness,” said Dr. Dishler at the annual meeting of the American Society of Cataract and Refractive Surgery. “It allows for a very precise correction without, to all appearances, any requirement for a nomogram. Visual recoveries have thus far been very rapid.”

Dr. Dishler

Dr. Dishler reported safety outcomes from the initial FDA clinical trial results for the ReLEx smile procedure for spherical myopia correction. The trial was conducted under an investigational device exemption for the femtosecond laser platform. The system has been used for several years in Europe, Asia, and other regions, Dr. Dishler said, but is still under investigation in the United States.

The procedure involves cutting precisely shaped lenticule from the stroma and removing it through a small incision. Unlike LASIK, no flap is required and tissue is physically removed with no ablation.

The FDA granted permission to study 100 eyes, of which 99 have been operated on. The manufacturer is currently collecting and processing data to support a request to study the remaining 260 eyes and follow the results for at least 1 year.

79 eyes included

Dr. Dishler’s initial report covered a total of 79 eyes in 79 patients. The approved treatment sphere range was 1 to 8 D with a cylinder of –0.5 D or less and MRSE of –8.25 D or less. This was a sphere-only study in single eyes with a change in MRSE of 0.5 D or less in the prior year in the eye to be treated. Patients were at least 22 years old and the optical zone was 6 to 6.5 mm.

Most of the patients, 60.8%, were female and the eyes were roughly balanced, 54.4% right and 45.6% left. The mean age was 35 years, the mean MRSE was –4.33 D, the mean sphere –4.25 D, and the mean cylinder –0.15 D.

“The results seem very promising,” he said. “The accuracy of correction is very good and is certainly within the ballpark of what is achieved with conventional LASIK-type procedures.”

The mean refraction 1 month postoperatively was MRSE –0.11 D, sphere 0.0 D, and cylinder –0.22 D. The mean results 3 months postoperatively were similar, MRSE –0.08, sphere 0.03, and cylinder –0.22. Most eyes, 98%, were within 0.5 D of spherical equivalent goal at 3 months and 100% of eyes were 20/40 or better. Most eyes, 98%, 20/25 or better and about 88% were 20/20 or better at 3 months.

Safety outcomes

Safety results were very good, Dr. Dishler noted. At 3 months postoperatively, no eyes had lost two or more lines of best spectacle-corrected visual acuity (BSCVA), fewer than 5% had lost one line, more than 50% were unchanged, about one-third had gained one line, and a handful of patients had gained two or more lines.

Intraoperative events were few and all resolved, he continued. A difficult lenticule removal resulted in a single radial cap tear. The tear was treated medically and resolved without sequelae. Suction was lost during the cap cut on one eye. The eye was re-docked and the procedure was completed successfully.

There were three cases of diffuse lamellar keratitis, all stage 2 or less. One case was seen 1 week postoperatively and was medically treated without sequelae. The patient had uncorrected visual acuity of 20/16 at 1 month and MRSE was plano.

Two cases were case was seen at 1 day postoperatively. Both were treated medically and both resolved without sequelae. Best uncorrected visual acuity at 1 week was 20/25 and BSCVA was 20/12.5 for both.

A single patient had transient light sensitivity syndrome at 2 months. It was treated medically and resolved without sequelae. Best uncorrected visual acuity at 3 months was 20/25, MRSE was –0.25, and BSCVA was 20/16.

“There are no ablation issues, such as drying in the cornea or hydration changes,” Dr. Dishler said. “This is a very different principle from LASIK. We are cutting and removing a specific shape based on the Munnerlyn-type formula, so there is no reason it shouldn’t be as accurate at higher amounts of nearsightedness as it is at lesser amounts.

“Excimer lasers seem to be less accurate in working with larger amounts of correction,” he added. “It is a new paradigm for the correction of nearsightedness which may, for certain patients, be preferable because the treatment is not subject to the amount of correction needed and it can be done using a small incision with all the obvious benefits of not requiring a flap.”

Jon Dishler, MD

E: jond@dishler.com

Dr. Dishler is a paid consultant for Carl Zeiss Meditec and a primary investigator for the VisuMax Myopia Study.

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