Article
Femtosecond lenticule extraction for myopia promising
Small Incision Lenticule Extraction (SMILE) performed using a femtosecond laser (VisuMax 500 kHz, Carl Zeiss Meditec) is being investigated as a treatment for spherical myopia in a U.S. clinical trial. Positive results were achieved in preliminary analyses of data from 315 eyes.
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Small Incision Lenticule Extraction (SMILE) performed using a femtosecond laser (VisuMax 500 kHz, Carl Zeiss Meditec) is being investigated as a treatment for spherical myopia in a U.S. clinical trial. Positive results were achieved in preliminary analyses of data from 315 eyes.
Dr. Doane
By Cheryl Guttman Krader; Reviewed by John F. Doane, MD
Kansas City, KS-Preliminary results from a U.S. clinical trial indicate that a proprietary, femtosecond laser-based refractive procedure is a safe and effective technique for achieving predictable and stable correction of spherical myopia.
Data from the study investigating SMall Incision Lenticule Extraction (SMILE) were reported by John F. Doane, MD, a clinical trial investigator at Discover Vision Centers of Kansas City. The procedure is not yet approved by the FDA in the United States
SMILE is performed using the VisuMax 500 kHZ femtosecond laser (Carl Zeiss Meditec) to create a refractive corneal lenticule in the stroma that is removed through a small side incision. Photodisruption time for lenticule creation is about 29 seconds.
Patients enrolled in the study have spherical myopia in the range from –1 to –10 D and up to –0.50 D cylinder, although cylinder is not being treated. SMILE is performed in one eye only, and the non-study eye is treated with an alternate refractive procedure, usually LASIK.
Planned enrollment is 340 eyes at five investigational sites. As of April 17, 2014, data were analyzed for 315 of 318 eyes treated; 120 eyes had reached the 6-month follow-up visit, 89 were seen at 9 months, and 52 were evaluated at 12 months. The patients enrolled so far have a mean age of 33 years and mean MRSE of –4.66 D with mean cylinder of –0.19 D.
“The refractive results being achieved with SMILE are on par with those for any excimer laser surgeries, and the predictability of the SMILE refractive outcome is equally good for all levels of myopia treated,” said Dr. Doane, clinical faculty, Department of Ophthalmology, Kansas University Medical Center, Kansas City. “Compared with LASIK, the visual recovery after SMILE is perhaps a day slower, but the functional outcomes at later follow-up intervals are also similar comparing SMILE and LASIK.
“However, there are some important differences between these procedures that may be considered advantages of SMILE,” he said. “The lenticule extraction procedure eliminates concerns about flap-related complications and should result in less dry eye and better corneal biomechanical stability.”
Treatment in a vacuum
In addition, the treatment is essentially done in a vacuum, within the cornea.
“Therefore, it is not affected by environmental factors, including temperature, barometric pressure, humidity, or particulate matter in the air, nor are we worried about treatment time and stromal drying as we are with open-air excimer laser ablations,” he said.
In addition to Dr. Doane, other investigators in the SMILE clinical trial include William Culbertson, MD and Sonia Yoo, MD, Bascom Palmer Eye Institute, University of Miami, Miami; Vance Thompson, MD, Sioux Falls, SD; John Vukich, MD, Dean Health Systems, Madison, WI; and Jon Dishler, MD, Greenwood Village, CO. Enrollment for the remaining 22 patients is continuing, and Carl Zeiss Meditec is preparing to submit a protocol for an FDA clinical trial evaluating treatment of myopia with astigmatism.
Safety data from the clinical trial show a few intraoperative and postoperative events. Dr. Doane observed that because SMILE is a completely new procedure, surgeons should expect a learning curve.
“The keys are to understand the three-dimensional anatomy of working in a pocket and to have the correct instruments for dissecting the lenticule,” he said. “Then, the procedure becomes straightforward and efficient with a little experience.”
John F. Doane, MD
This article was adapted from Dr. Doane’s presentation at the 2014 meeting of the American Society of Cataract and Refractive Surgery. Dr. Doane is a consultant for Carl Zeiss Medtec and receives funding for research overhead.
