Background
Small incision lenticule extraction (SMILE) is a flap-free refractive surgery, in which the corneal stromal lenticule is cut by a femtosecond laser and removed through a small corneal incision tunnel. Recently, SMILE has been proposed as an alternative to LASIK or PRK, which has been a popular refractive surgery technique for a decade because the visual outcome has proved to be generally good and the time to return to normal life after surgery is short.
However, complications after surgery can include dry eyes, corneal haziness, ectasia, and traumatically loosened flaps; SMILE is expected to remedy these shortcomings. Studies have shown that compared with LASIK, SMILE minimizes dry eye, while maintaining higher corneal sensitivity and cornea tensile strength after surgery. Therefore, SMILE is considered a good alternative form of refractive surgery, especially when the degree of myopic correction is large or the cornea is thin.
There have been numerous studies on SMILE outcomes, but most reported short term results based on6 months or less of follow up with small numbers of samples. Longer-term studies with larger sampling sizes are necessary to establish the full capability of SMILE. Specifically, no study has compared the outcomes of SMILE as regards the degree of myopia. In this study, 1-year SMILE results for mild- to moderate-myopic patients (<−6.0 D) were compared with those for high-myopia patients (≥ − 6.0 D) in terms of efficacy, predictability, and safety.