History and Results; Indications and Contraindications of SMILE Compared With LASIK.

Small incision lenticule extraction (SMILE) is a new paradigm for refractive surgery, and was first performed by Sekundo and Blum in 2008. It uses only a femtosecond laser to carve out a lenticule within the corneal stroma, and then achieves refractive correction by extracting the lenticule through a small incision. A number of studies have shown that SMILE leads to stable and efficacious outcomes, combined with high safety. Long-term studies also indicate that SMILE has excellent outcomes combined with high safety. Although relatively safe, SMILE can have some intraoperative and postoperative complications, including suction loss during the procedure, lenticule tears, incision tears, epithelial ingrowth, diffuse lamellar keratitis, and residual refractive error. Studies indicate that SMILE leads to less postoperative dry eyes. It is thus preferred over laser-assisted in-situ keratomileusis (LASIK) in cases wherein there is mild dry eye preoperatively. It is also preferred over LASIK in cases wherein the patient is likely to engage in contact sports. LASIK may be preferred over SMILE for the treatment of hyperopia, and in cases of significant higher order wavefront aberrations or topographic irregularities.