Treatment range for SMILE:

Currently the SMILE treatment range is for pure myopia from −0.50 D to −10.0 D (SEQ) and for myopic astigmatism up to −5.0 D. Hyperopic SMILE treatments are not commercially available yet (Fig. 3.2).

General preparation of the patient:

Samples of surgical instruments for SMILE from GENDER and MALOSA are shown in Figs. 3.21–3.24.

A curved contact glass (size S or M; mostly S depending on the corneal size) is fixed at the laser opening and automatically calibrated. Next steps: Routine local disinfection periocular, application of local anesthetic drops, coverage of eyelashes with sterile drape, placement of eyelid speculum, flushing with BSS and aspiration of pooled fluids and secrets out of the fornix for a clean corneal surface. Then the patient’s eye is moved towards to the contact glass by lifting the bed, and the contact glass is gently docked on the corneal surface (Fig. 3.3). Be sure that the contact glass has free access to the cornea and that there is no touch with a prominent nose, the speculum or orbital bones. If there is need you can move the head rest of the bed up and down, elevate the chin or turn the face in the opposite direction. Watch out that the patient’s head is lying straight and comfortable.

The big advantage of the curved contact glass (Fig. 3.4) is that there is no strong applanation but only soft acurvation of the corneal surface. Thus we have only a low increase of the intraocular pressure and a minimized tissue distortion during the whole suction procedure. Moreover, the advantage is that with this soft docking the patient fixation is maintained during the whole laser procedure but with the risk of suction loss if the contact glass is not docked properly.

During the docking procedure the patient has to cooperate by fixating a green blinking light (Fig. 3.5); this guarantees a perfect centration of the contact glass and consequently an exact centration of the lenticule onto the visual axis. After more than 90 % of contact between cornea and contact glass you press the suction button; be sure that there is hardly any fluid and Meibom’s secret between cornea and contact glass.

After the VISUMAX confirms the end of a correct suction procedure with the word “ready” you press the foot switch and the laser application is starting. First the laser prepares the refractive part of the lenticule (= backside of the lenticule) with a spiral starting from outside (Fig. 3.6) followed by the lenticule’s side cut. Typically the optical zone of the lenticule is between 6 and 7 mm (standard is 6.5 mm).

Second, the VISUMAX is preparing the front side of the lenticule (Fig. 3.7) which is a plane-parallel spiral cut starting from inside (Fig. 3.7). The laser procedure is finished by the incision preparation with a size of 2–4 mm (free choice). Normally the cap diameter is chosen between 7.3 and 7.8 mm (Figs. 3.8 and 3.9). When the procedure is finished suction is released automatically. The whole suction time including the laser application takes not more than 30–35 seconds depending on the diameter.

Be sure that you have the correct spot and track distance and an optimized spot energy; this guarantees a minimum of opaque bubble layer (OBL) and consequently an easy mechanical dissection of the residual micro-bridges of the lenticule. As the energy levels are specific and different for each device your application specialist from ZEISS will instruct you at the beginning (standard energy levels are between 150 and 170 nJ per spot depending on each single device).

For an easy lenticule dissection you first open the incision with a Sinskey hook or similar. Next you prepare two small pockets (1 × 1 mm) with the hook – one in the front and one in the back plane of the lenticule. This is most important. For an uncomplicated dissection of the lenticule you have to ensure to start the dissection with the front side of the lenticule first followed by the backside. The dissection is to be done with gender swinging moves all over the whole expanse of the pocket (Fig. 3.10). If there is need you can fix the bulb with a scleral micro-forceps.

After a complete dissection the lenticule is easily extracted with a forceps (Fig. 3.11). Please check that the lenticule is removed in total (you can place it on the cornea and spread it out and check whether edges are intact and circular). Few surgeons prefer to irrigate the interface with BSS, others don’t. Post-operative application of combined antibiotic and steroid eye drops is recommended four times per day for 1 week. As SMILE is a flapless procedure there is no need for eye patches or eye shields after surgery. Regular follow ups are recommended after 1 day, 1 week and 1 month.