EyeWorld Asia-Pacific June 2016 Issue

EWAP SECONDARY FEATURE 27 June 2016 by Liz Hillman EyeWorld Staff Writer Skills and know-how necessary for successful SMILE outcomes SMILE shows promise, but surgeons should be well- trained and versed in the management of technical complications S mall incision lenticule extraction (SMILE) might be an option for refractive surgery with some benefits compared to LASIK, but ophthalmologists should expect a learning curve for the procedure and be aware of its possible complications and how to manage them. Still in clinical trials in the U.S. but CE mark approved in 2009, Dan Reinstein, MD, London Vision Clinic, said advantages of SMILE include faster dry eye recovery and better spherical aberration control, allowing an extended range of treatment. “Both of these advantages stem from the nature of the opening through which the procedure is performed—a minimally invasive pocket incision—as this results in maximal retention of anterior corneal innervation and structural integrity,” Dr. Reinstein said of the procedure, which uses a VisuMax 500 kHZ femtosecond laser (Carl Zeiss Meditec, Jena, Germany). “There are also benefits from the patients’ perspective as they are immediately attracted to the flapless nature of the procedure, meaning that the risk of flap it is managed. “If suction loss occurs during the lower interface, it is a simple case of reprogramming the case with a thinner cap, and SMILE can be performed as normal without any risk of crossing the original interface,” Dr. Reinstein said. “If the suction loss occurs during the creation of the tunnel (i.e., after the lenticule has been created completely), then suction can be reapplied and the femtosecond ablation for the tunnel only can be safely performed. “If the suction loss occurs during the upper lenticule interface creation, the surgeon needs to carefully consider whether the procedure can be finished by repeating the upper interface creation, or whether the patient needs to be switched to SMILE at a more superficial cap depth, LASIK, or PRK,” Dr. Reinstein explained. He added that it’s important to know how to identify the upper interface if the lower interface is accidentally dissected first. “This can be simply achieved by inserting the Sinskey tip sideways into the incision, rotating the tip upward to engage the lenticule edge, and moving in a nasal direction to release the lenticule edge,” he said. “Without this technique, some surgeons have had to unnecessarily switch the patient to PRK. It is also dislocation is eliminated. “It is important to point out that while SMILE has a benefit associated with corneal biomechanics, the procedure still reduces the overall tensile strength of the cornea. The advantage is that it does so less than LASIK and PRK. Following the publication of cases of ectasia after SMILE in eyes with forme fruste keratoconus, it has become apparent that a distinction must be stressed— keratoconus is and always has been a relative contraindication to tissue subtractive procedures, which should only be carried out in certain circumstances with concomitant crosslinking and proper informed consent,” Dr. Reinstein said. Techniques to improve out- comes Although he called the procedure “relatively straightforward,” Dr. Reinstein said surgeons should have training in the specific SMILE technique. “The surgical technique and femtosecond laser settings are probably the most important factors for achieving the best result,” he said. “While this will not affect the long-term result, the visual quality in the early postoperative period will be maximized by using the optimal laser settings for the individual laser (energy, spot size, spot spacing) and by minimizing the trauma to the stromal interface.” Proper centration of the calibrated curved contact glass of the femtosecond laser and the cornea is important as well. When these two come into contact, a meniscus tear film appears and the patient is able to see the fixation target very clearly, Dr. Reinstein said. As the patient looks at this target, corneal suction fixes the eye into place, which Dr. Reinstein said “essentially autocentrates the visual axis and hence the corneal vertex to the vertex of the contact glass, which is centered to the laser system, and the center of the lenticule to be created.” The surgeon then confirms centration, comparing it to the positions of the corneal reflex and pupil center to a Placido eye image. If centration is unsatisfactory, the surgeon can release suction and repeat the procedure. To avoid “mud crack-type microfolds in the cap” after the lenticule is extracted, Dr. Reinstein said he uses a dry micro-spear to “redistribute any redundant portions of the cap evenly to the periphery, performed with fluorescein staining at a slit lamp in the OR immediately after the procedure.” Managing complications The most common intraoperative complication in SMILE is loss of suction during femtosecond ablation. Exactly when this occurs determines how continued on page 28