Researches showed that femtosecond laser corneal small incision lenticule extraction (SMILE) was used in the correction of myopia and myopic astigmatism due to its fast recovery, good short-term efficacy and few complications.However, few research focused on its long-term efficacy.

This study was to evaluate the effectiveness, safety, predictability, stability and complications of SMILE.

A serial cases-observational study was carried out under the approval of Ethic Committee of Henan Eye Institute and informed consent of patients.Sixty-seven eyes of 34 patients with myopia and myopic astigmatism were included in Henan Eye Institute from January to June 2013.All the patients received SMILE and followed-up for 2-year duration.The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), automatic optometry, intraocular pressure and corneal topography were examined before surgery and 1 day, 1 week, 1 month, 3 months, 1 year and 2 years after surgery and calculated the spherical equivalent (SE). The long-term efficacy of SMILE included effective index (preoperative BCVA/postoperative UCVA), safety index (postoperative BCVA/ preoperative BCVA), predictability (linear regression analysis between actual SE and attempted SE) and refractive stability (SE changes at postoperative time points).

The preoperative BCVA was ≥20/20 in 60 eyes with the percentage of 89.55%.UCVA≥20/20 were found in 61 eyes and 60 eyes in postoperative 3 months and 2 years respectively (91.04% and 89.55%). The effective index was 1.038±0.182 and 1.029±0.231 in postoperative 3 months and 2 years respectively, showing an insignificant difference between them (t=0.400, P>0.05). Compared with the preoperative BCVA, 8.96% (6/67) and 10.45% (7/67) eyes lost 1 line at 3 months and 2 years after surgery, respectively.The safety indexes were 1.141±0.193 and 1.312±0.242 at 3 months and 2 years after surgery, with no significant difference between them (t=0.414, P>0.05). A linear correlation was found between actual SE and attempted SE both at postoperative 3 months and 2 years, with the linear regression equations of Y=0.897 1X-0.440 8 (R²=0.914 2, P<0.05) and Y=0.893 7X-0.382 3 (R²=0.915 7, P<0.05), respectively.The SE was (0.013±0.578), (-0.033±0.489), (-0.106±0.508), (-0.103±0.375), (-0.154±0.518) and (-0.147±0.366)D 1 day, 1 week, 1 month, 3 months, 1 year and 2 years after surgery, respectively, and there were no significant difference among different time points (F=0.185, P=0.176). Eighteen in the 67 eyes occurred opaque bubble layer after surgery.Diffuse lamellar keratitis appeared in 6 eyes and punctate keratitis was in 2 eyes.These complications were cured 1 month after administration of drugs.

SMILE is good in effectiveness, safety, predictability and refreactive stability and has fewer complications during 2-year following-up.

Corneal stroma/surgery; Laser therapy; Treatment outcome; Myopia/surgery; Astigmatism/surgery; Femtosecond laser; Corneal lenticule extraction; Small incision; Human