SMILE Lenticule Removal Technique

The same surgeon (CYT) performed all surgical procedures. A VisuMax® 500-kHz femtosecond laser was used for SMILE treatment (frequency: 500 kHz; cut energy index: 180 nJ pulsed; spot spacing: 4.5 μm). The lenticule diameter was 6.5 mm and the cap diameter was 7.5 mm. The intended thickness of the cap was 110 μm, and the incision was 2.0 mm long at the 11 o’clock position. The lenticule was separated using a straight, blunt spatula. The traditional method has been described previously [2 (link)].
The Chung’s swing technique procedure is described in the following. The lenticule–stromal bed interface (i.e., the lower lenticule interface) is separated with a fan-shaped spatula,without grasping the conjunctiva with forceps. The spatula ascends to the lenticule-cap interface by lifting and swinging at the left end of the incision. After the lenticule-cap was separated into a fan shape, McPherson forceps (M. Blum design; Geuder, Heidelberg, Germany) grasp the lenticule margin at 12 o’clock; the lenticule is pushed towards the center of the cornea and pulled, to remove the lenticule in a clockwise direction. Because there is mild resistance at the 12–3 o’clock positions and 8–11 o’clock positions for lenticule movement and removal, push and pull of the lenticule requires some effort (Figs. 1 and 2) (Additional file 1). Both the lenticule-stromal bed and the lenticule-cap interface were completely separated, except at the 12 o’clock to 3 o’clock and the 8 o’clock to 11 o’clock positions, to avoid damage by forceps during lenticule extraction. In the case of a ripped lenticule, McPherson forceps were inserted again to remove the lenticule remnant.Fig. 1

Diagram of the steps of the Chung’s swing technique. a The lenticule–stroma interface was dissected in a fan-shape using a spatula. b The spatula ascended to the lenticule–cap interface by lifting and swinging at the left end of the incision. c The lenticule–cap interface was dissected in the same way. d The lenticule was extracted by McPherson forceps. After grasping the lenticule margin at 12 o’clock, the lenticule was pushed and pulled to the center of the cornea

Fig. 2

Intraoperative photographs of the Chung’s swing technique. a Dissection of the lenticule–stroma interface in a fan-shape. b Ascending the spatula to the lenticule–cap interface. c, d Dissection of the lenticule–cap interface by swinging the spatula. e Pushing the forceps anteriorly with strength. f Pulling the forceps posteriorly with strength

After removing the lenticule, the stromal pocket was flushed with balanced salt solution (BSS®, Alcon, Fort Worth, TX, USA). After surgery, all patients were treated with 0.5 % moxifloxacin (Vigamox®, Alcon) for 5 days, a 0.1 % fluorometholone (Ocumetholone®, Samil, Seoul, Korea) for 2 weeks, and preservative-free hyaluronic acid lubricating drops (Hyalein Mini 0.1 %®, Santen, Osaka, Japan) for at least 2 weeks.