The 2-year efficacy study of femtosecond laser corneal small incision lenticule extraction for correction of myopia and myopic astigmatism

Abstract

Background 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. Objective This study was to evaluate the effectiveness, safety, predictability, stability and complications of SMILE. Methods 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). Results 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. Conclusions SMILE is good in effectiveness, safety, predictability and refreactive stability and has fewer complications during 2-year following-up. Key words: Corneal stroma/surgery; Laser therapy; Treatment outcome; Myopia/surgery; Astigmatism/surgery; Femtosecond laser; Corneal lenticule extraction; Small incision; Human