Corneal Topographic and Biomechanical Changes after Small Incision Lenticule Extraction (SMILE) In Myopic Eyes

Abstract

Background: Small incision lenticule extraction (SMILE) offers laser vision correction by using a less invasive technique that creates a lenticule inside the intact cornea. This procedure limits the biomechanical strength of the cornea and reduces flap-induced complications. Purpose: To evaluate outcome, post-operative corneal topographic and biomechanical changes in myopic patients who had undergone SMILE. Methods: The study included 40 eyes of 20 patients treated by SMILE for myopia and myopic astigmatism. Data included uncorrected and best corrected visual acuity (UCVA and BCVA), spherical equivalent (SE), central pachymetry Pentacam (oculus) topography to evaluate changes in keratometric readings (K1 and K2) and asphericity (Q). Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with ocular response analyzer. Patients were treated and followed for 12 months. Results: SMILE procedure for the correction of myopia and myopic astigmatism was performed on 40 eyes of 20 patients. There was highly significant difference between pre and postoperative keratometric regarding K1 and K2 was change from 42.9 ± 0.82 and 39.8 ± 1.14 to 43.9 ± 1.21 and 40.5 ± 1.18 respectively (P value <0.001).Corneal resistance factor and hysteresis were also change from 11.55 ± 1.29 mm Hg and 11.68±1.40 mm Hg to 9.47 ± 1.29 mm Hg and 8.49 ± 1.54 mm Hg, respectively) (P < .0001). At the end of follow up UDVA was 20/20 or better in 86 % of eyes. Conclusions: Biomechanical stability with small-incision lenticule extraction has been demonstrated with establishment of myopic and astigmatic corrective ability, so SMILE represents a safe and effective refractive option. The incidence of intraoperative and or postoperative complications remains minimal. Although visual recovery may be slower than LASIK in most cases.