March 2019


Refractive corrections
What’s next for SMILE after new approvals

by Liz Hillman EyeWorld Senior Staff Writer

The lenticule is extracted after dissection in SMILE.
Source: Jon Dishler, MD

Older laser settings with spots closer together and higher overall energy deposition leads to a “fluffy” lenticular side cut (small arrow) and a large amount of opaque bubble layer (OBL) in the visual axis (large arrow).
Source: Rex Hamilton, MD

Newer laser settings with spots further apart and lower overall energy deposition leads
to “clean” lenticular side cut (small arrow) and a small amount of OBL in the visual axis (large arrow).
Source: Rex Hamilton, MD


“I think as we move forward and SMILE becomes more accepted and the knowledge expands in our patient base, we will be migrating more toward SMILE in the future.”
—Rex Hamilton, MD

Patient population for SMILE expanded to include astigmatism; new parameters speed recovery

Last year, the U.S. Food and Drug Administration (FDA) approved new indications and modalities for small incision lenticule extraction (SMILE) that not only expanded indications of the procedure but could result in faster visual recovery.
In October 2018, just over 2 years since its initial FDA approval, Carl Zeiss Meditec (Jena, Germany) announced the FDA approval of the ReLEx SMILE procedure to treat up to 3 D of myopic astigmatism. While this opens the procedure, which involves use of the VisuMax femtosecond laser (Carl Zeiss Meditec) to create a customized lenticule that is then extracted through a side pocket, to more patients, Rex Hamilton, MD, Santa Monica Eye Medical Group, Santa Monica, California, said U.S. surgeons are also now able to use a smaller incision size and other new parameters.
“We have the smaller incision going from 90 degrees down to 60 degrees, and maybe most importantly, we have the outside U.S. parameters in terms of the spot spacing and energies. We are able to now widen the spot spacing, which allows for an overall lower energy deposition when we create the lenticule, offering a dramatic advantage with regard to how fast the vision recovers,” Dr. Hamilton said.
Dr. Hamilton said that with these new parameters visual recovery to 20/20 is usually 1 to 2 days, as opposed to 1 to 2 weeks with the original FDA-approved parameters.
“With the new settings, I have been able to lower the overall energy deposition by 57%. With this significant reduction in energy, dissection planes are cleaner and smoother, and there is less opaque bubble layer in the visual axis, which hastens the settling of the tissue planes. This has translated directly to faster vision recovery in my patients. The vast majority of my patients are now seeing 20/20 on postop day 1,” Dr. Hamilton said.
“That has made a big difference in terms of patient acceptance and the confidence of the surgeon to be able to recommend the procedure,” he added.
In addition to bringing astigmatic correction to a new patient population for SMILE, Dr. Hamilton and Jon Dishler, MD, Dishler Laser Institute, Greenwood Village, Colorado, think SMILE is attractive to certain patients based on factors that have nothing to do with their refractive error.
“The best candidates seem to be the millennial generation for a variety of reasons,” Dr. Dishler said, a few of them being less discomfort, fewer postop issues, and a faster return to all activities. “There is crossover [with the LASIK population] but an additional group [seems to be] drawn to SMILE.”
From a physical standpoint, Jason Stahl, MD, Durrie Vision, Overland Park, Kansas, thinks that LASIK and SMILE candidates comprise the same patient population, though he, Dr. Hamilton, and Dr. Dishler think SMILE has the ability to treat higher myopes.
“Now that we have the 60-degree side cut incision, biomechanically we are not altering the cornea to the level that we do with LASIK with a 270-degree plus incision, so we are able to treat higher corrections in patients who we may not have been comfortable treating with LASIK,” Dr. Hamilton said. “Those patients used to be relegated to PRK, which is a fine procedure but has a long recovery in terms of the vision and is not an optimal choice for most patients.”
Ultimately, if a patient is an overall candidate for laser vision correction, choosing the right procedure for them comes down to the patient’s lifestyle and personal needs, Dr. Stahl said.
Dry eye symptoms related to surgery also seem to resolve quicker with SMILE compared to LASIK, Dr. Hamilton said. He said he warns LASIK patients of the potential for dry eye symptoms for 6 to 12 months, whereas SMILE patients seem to see a resolution of these symptoms between 1 and 3 months.
“That’s huge. [Dry eye] is another barrier. … The fact that we now have a tool that directly addresses that concern is very attractive to patients,” Dr. Hamilton said.
“SMILE has broad appeal, but it is particularly well-suited for high myopes with extremely good accuracy, certain occupational professions such as first responders, and sports enthusiasts. It also seems to be beneficial for dry eye, although not proven as an indication,” Dr. Dishler said, summarizing his thoughts on the SMILE patient population.
On the flip side, patients who might be better suited to LASIK, Dr. Hamilton said, are low myopes.
“It is still a bit of a technical challenge to dissect a very thin lenticule,” he said. “I would still recommend LASIK at the very low end of myopia, but with regard to moderate to high myopes with up to 3 D of astigmatism, I am offering SMILE to those patients as my primary choice.”
Though a laser refractive procedure, like LASIK, Dr. Hamilton and Dr. Dishler noted a learning curve with SMILE. To get over this learning curve, Dr. Hamilton recommended working with an experienced mentor on your first cases, scheduling several back-to-back bilateral SMILE cases, and taking a course at an ophthalmic meeting. Dr. Hamilton also recommended becoming familiar with the VisuMax laser by performing several dozen LASIK flap cases before moving on to your first SMILE cases.
“The other key point with SMILE is … we are treating the refractive error with this procedure, so the centration of the SMILE lenticule is significantly more critical than the centration of the LASIK flap,” Dr. Hamilton said, noting that he uses a printout from the Galilei topographer (Ziemer, Port, Switzerland) to show centration on the visual axis, which he uses as a visual representation of where he wants to see the fixation target within the pupil while centering the eye with the VisuMax laser.
Take your time with your early SMILE cases, Dr. Hamilton said, stressing that speed with this procedure will come with experience.
“It’s amazing how fast it can be, but taking your time initially is important. It’s amazing with each of your first 20 to 30 cases how much more you see with each case with regard to instrumentation, bubble pattern, depth, and tactile feedback. All of those things are new, so taking your time is very important,” he said.
In terms of the new modalities, Dr. Stahl said if you are experienced in treating spherical corrections with the larger incision, there is not much of a difference to adding astigmatic correction or going to a smaller incision. “There are advantages in marking the cornea in helping alignment of the treatment … but aside from that, it’s essentially the same procedure,” he said.
Though the need for post-SMILE enhancement is rare—in the nearly 2 years and nearly 300 cases he has performed, Dr. Hamilton has performed one enhancement—there are options. He used PRK in this case, but said very thin flap LASIK is an option as well. However, he cautioned that given the required 120 µm cap thickness for SMILE in U.S. cases, you need to be careful with a LASIK enhancement on a SMILE cap. Dr. Stahl has also only performed one enhancement in his 2 years with SMILE, also using surface ablation in this case.
Still only a few years from its initial FDA approval, Drs. Hamilton and Dishler said some patients are coming in requesting SMILE, but Dr. Hamilton said they are not the majority, though he, Dr. Dishler, and Dr. Stahl expressed that they expect that to shift with time.
“I think, in 2019, the ability to have the three different procedures available to offer patients is very useful,” Dr. Hamilton said. “I think as we move forward and SMILE becomes more accepted and the knowledge expands in our patient base, we will be migrating more toward SMILE in the future.”

Editors’ note: Drs. Hamilton and Dishler have financial interests with Carl Zeiss Meditec. Dr. Stahl has no financial interests related to his comments.

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