Visumax femtosecond laser system

All SMILE procedures were performed by the same surgeon (YYB) using the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany). The routine procedures of the SMILE surgery have been described in a previous study [12 (link)]. In this study, the laser cut energy index was 155 nJ; the intended cap thickness was 110 μm to 140 μm; the programmed optical zone diameter was between 6.1 and 6.5 mm; and the diameter of the cap was 1 mm larger than the diameter of the lenticule. The optical zone and cap thickness were selected on the basis of the pupil diameter and percent tissue alert (PTA). A recommended nomogram adjustment was implemented for all subjects. To achieve emmetropia, the nomogram adds 10% correction of spherical refractive, as suggested by the manufacturer and as is the similar experience of other surgeons [13 (link), 14 (link)]. The predicted lenticule thickness, following the nomogram adjustment, was displayed by the VisuMax software and recorded for statistical analysis.

All surgeries were performed under local anesthesia by one surgeon (Hao Zhou) with patients undergoing either SMILE or FS-LASIK.
SMILE was performed using the VisuMax femtosecond laser system (Carl Zeiss Meditec) with a repetition rate of 500 kHz, pulse energy of 185–190 nJ, intended cap thickness of 100–120 μm, cap diameter of 7.5 mm, lenticule diameter of 6.1 to 6.6 mm (depending on the refractive error), and a 90°-angle side cut with a circumferential length of 2.1 mm at the superior position.
FS-LASIK was performed with the VisuMax system for flap creation followed by Mel 80 excimer laser (Carl Zeiss Meditec) for stromal ablation, with an intended flap thickness of 95 μm and pulse energy of 185 nJ. The hinge was located at the superior position.
A standard postoperative topical steroid (Fluorometholone 0.1%) was tapered over 30 days; topical antibiotic (Tobramycin 0.003%) QID for 7 days, and unpreserved ocular lubricant 4 times a day was prescribed for a month.

Human corneal tissues were obtained from Santa Lucia International Eye Bank (Manila, Philippines). Approval from the Institutional Review Board of the Hospital Ethics Committee was obtained for the study, and the Declaration of Helsinki was followed. Corneal tissue was positioned under the VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) using an artificial anterior chamber, and samples were regularly cut to 8 mm wide and 100 μm thick.

All SMILE procedures were performed under topical anesthesia and aseptic conditions by the same team of experienced surgeons using the VisuMax femtosecond laser system (Device version 2.10.14; Carl Zeiss Meditec AG, Jena, Germany). The repetition rate and pulse energy were 500 kHz and 130 to 150 nJ, respectively. In all eyes, the intended cap thickness was 110 to 130 μm, the cap diameter was 7.5 to 7.6 mm, and the optical zone of the refractive lenticule was between 6.5 and 6.8 mm. The lenticule was then detached and removed through a 2 mm lateral incision at 120^°, and postoperative residual stromal bed thickness was at least 280 μm. The surgical technique was the same for all patients and the duration of the procedure was 10 to 15 min. All patients received 0.5% levofloxacin eye drops for 1 week, 4 times a day, and 0.1% fluorometholone eye drops for 4 weeks with weekly tapered doses. No significant complications were observed during postoperative follow-up.

SMILE was performed using a 500 kHz VisuMax femtosecond laser system (Carl Zeiss Meditec AG, Jena, Germany) in expert mode at the following settings for all the eyes: pulse energy of 130 nJ, corneal cap thickness of 100 μm, and optical zone diameter of 6.2–6.8 mm (depending on the preoperative corneal thickness and the refractive error to be corrected). The side cuts were set to 90° (12-o'clock position) with 2.0-mm circumferential width at the superior position. The technical procedure was conducted as previously described (11 (link)).
FS-LASIK was performed using a 500 kHz VisuMax femtosecond laser (Carl Zeiss Meditec AG, Jena, Germany) for flap creation and a 250 Hz MEL-80 excimer laser (Carl Zeiss Meditec AG, Jena, Germany) for stromal ablation at the following settings for all the eyes: pulse energy of 185 nJ, flap diameter of 8.0 mm, flap thickness of 90 μm, hinge length of 4.0 mm, and optical zone diameter of 6.2–6.8 mm. In all patients, bandage soft contact lenses (ACUVE OASYS, Inc., FL, USA) were applied for 1 day after surgery.
All surgeries were performed by the same skilled surgeon in both procedures (XZ).
Both groups received the same postoperative topical medications: levofloxacin 4 times per day for 7 days; 0.1% fluorometholone 8 times per day tapered to 1 time per day over 24 days, and artificial tears 4 times per day for 1 month.