*8.1.1 Ablative procedure*

FSLs are used in various refractive surgery procedures such as FSL-assisted laser in LASIK, refractive lenticular extraction (RELEX), and small-incision lenticule extraction (SMILE) (**Figure 9**). During LASIK procedure, first, a corneal flap is created by FSL; for this purpose, the laser spot moves inside the cornea at a programmed thickness, and by a perfect cut, the lamella is created. Then, the FS bundle continues along the flap circumference, and the flap is lifted; then, excimer- or solid-state UV-laser energy is used to change the cornea's refractive power by flattening or steepening the stromal bed. Later, the flap is repositioned.

Advances in FS laser technology, including the availability of fast-firing rates, enabled smaller spot sizes and tighter spot separation, which made sweeping and lifting of the flap easier. A well-fitting manhole is also enabled by the vertical side cuts of FSL. Compared with the traditional photo-refractive keratectomy, LASIK

### **Figure 7.**

*Considerable applications of different techniques of femtosecond laser (Left) and outstanding clinical usages (Right); SMILE: Small Incision Lenticule Extraction; PK: Penetrating Keratoplasty; LK: Lamellar Keratoplasty; EK: Endothelial Keratoplasty; Femto LASIK: Femtosecond-assisted (Femto) Laser In-Situ Keratomileusis (LASIK).*

 **Figure 8.**  *Femtosecond laser cut.* 

 **Figure 9.**  *Lenticule cut via femtosecond laser.* 

(using IntraLase™) showed to have a shorter rehabilitation period, more predictable flap thickness, better astigmatic neutrality, less epithelial injury, and faster stabilization of visual outcome; but is associated with a higher risk of dry eye and flap-related complications, such as transient light-sensitivity syndrome after surgery and diffuse lamellar keratitis in the flap interface. Nonetheless, the risk of dry eye and visual loss (related to intraocular pressure) in FS-LASIK is less than the conventional microkeratome-assisted LASIK. In lenticule extraction, FSL system is used for cutting a small lenticule in corneal tissue, and similar to the flap created in LASIK, the flap is lifted, the lenticule is removed, and then the flap is repositioned. Also, in the SMILE
