The introduction of small-incision lenticule extraction (SMILE) has given refractive surgeons an additional option to choose from when selecting the best vision correction procedure for their patients. As more surgeons begin the journey toward mastering SMILE, new pearls for techniques are slowly coming to light.
The standard SMILE technique involves docking and application of VisuMax femtosecond laser (Carl Zeiss Meditec) treatment to create an intrastromal lenticule, followed by lenticule dissection and extraction. The lenticule is separated from the surrounding stroma by blunt dissection via the small side-cut incision, first in the anterior plane and then in the posterior plane. This article presents a case that highlights the crucial step of correctly identifying the planes prior to dissection and offers clues for knowing when the posterior plane has been dissected before the anterior plane.
THE CASE
A 23-year-old woman presented to one of my colleagues for refractive consultation. She had used soft contact lenses in the past but found them to be uncomfortable. After discussion of the options, the patient opted to undergo SMILE in both eyes, noting her active lifestyle and concern about dry eye as motivating factors.
Her manifest refraction was -3.25 -0.75 X 170° OD and -3.00 -1.00 X 180° OS, mean keratometry was 40.95 D OD and 41.50 D OS, and central corneal thickness was 490 µm OD and 495 µm OS. Her medical and ocular histories were otherwise unremarkable.
The femtosecond laser treatment for the patient’s right eye was programmed at -3.35 -0.75 X 170°. The optical zone was set at 6.0 mm with a 0.50-mm transition zone. The femtosecond laser portion of the procedure was completed without complications. The surgeon began the procedure by attempting to identify the anterior plane followed by the posterior plane. Early on, the surgeon encountered a challenge when trying to identify the posterior plane and made multiple attempts with excessive force to complete this step.
Eventually, the surgeon felt that the planes had been identified and proceeded to try to dissect the anterior plane, again making multiple attempts. It initially appeared that the surgeon was able to successfully dissect both planes, but when he attempted to remove the lenticule he could not retrieve it. The procedure on the right eye was aborted at that time, and the left eye was successfully completed during the same session.
IN HINDSIGHT
After reviewing the video footage, the surgeon was able to identify that the anterior plane was never dissected. Instead, the posterior plane was identified and dissected first. Having realized his error, the surgeon reoperated 1 week later and, to the delight of the patient, was able to retrieve the lenticule by successfully dissecting the anterior plane. As shown in the video above, during lenticule dissection surgeons can take note of bubbles in the anterior plane and the double ring sign to ascertain whether they are in the anterior or posterior plane.
This case highlights how important it is to correctly identify the planes prior to dissection. My main takeaway from this surgeon’s experience is to pay particular attention to turning the Sinskey hook anteriorly when moving from the cap edge over the anterior lenticule in order to successfully identify the anterior plane first.
