Bolstered by its advantages as a treatment of myopia and myopic astigmatism, small-incision lenticule extraction (SMILE) has grown in popularity since its debut in 2012 and its subsequent approval from the US Food and Drug Administration in September 2016, according to a review researchers published in Seminars in Ophthalmology.
Studies have indicated that SMILE provides a better intraoperative patient experience because of the techniques involved, the researchers said. For example, the laser used in SMILE prompts a low rise in intraocular pressure. This helps prevent amaurosis fugax, which has occurred with laser-assisted in situ keratomileusis (LASIK), they said.
Also, LASIK requires an excimer laser for tissue ablation and a femtosecond laser for flap creation while SMILE requires only one laser platform. SMILE requires a smaller incision and leaves the anterior stroma intact, according to the researchers.
The smaller incision that SMILE creates in the anterior cornea may limit the dry eye symptom that is commonly associated with LASIK, which involves more surface exposure and disruption of the corneal subbasal and superficial stromal nerve bundles, they said.
Researchers pointed to one particular study that evaluated the tear breakup time and Schirmer testing after both SMILE and LASIK preoperatively and at 1, 3, and 6 months postoperatively. Although all parameters became worse in the early postoperative period in both groups, dry eye parameters were significantly better in the SMILE group relative to the LASIK group at 6 months.
The review also included data from studies showing the patient intraoperative experience. This research compared light perception, levels of anxiety, fear, and discomfort in patients treated with SMILE in one eye and LASIK in the other. While discomfort scores were higher during tissue manipulation in SMILE than flap lifting in LASIK (P =.020), they were comparable during docking and laser application (P >.249). Additionally, fear scores were lower in SMILE than LASIK during docking, although they were similar during occasional visual blackout, laser application, and lenticule or flap manipulation (P >.364).
The researchers noted that SMILE is not indicated for hyperopia, astigmatism greater than 3.0 D, or myopic astigmatism SE greater than -11 D. Excimer lasers are used for refractive enhancements after SMILE, they said.
Ahmed AA, Hatch KM. Advantages of Small Incision Lenticule Extraction (SMILE) for Mass Eye and Ear Special Issue. Seminars in Ophthalmol. Published online September 6, 2020. doi: org/10.1080/08820538.2020.1807028