A Clinical Study Of Small Incision Lenticule Extraction For The Correction Of Myopia And Astigmatism

Objective:To compare the clinical outcomes of small incision lenticule extraction (SMILE) and Femtosecond assisted LASIK (FS-LASIK), Sub-Bowman keratomileusis (SBK), LASIKin treating myopia and astigmatism.Method:This was a prospective clinical controlled study.81eyes of43patients were treated with SMILE,97eyes of49patients were treated with FS-LASIK,82eyes of44patients were treated with SBK, and78eyes of40patients were treated with LASIK. To evaluate visual quality, dry eye and biomechanical stability, the visual acuity,the manifest refraction, higher-order aberrations (HOAs), the contrast sensitivity (CS), the Schirmer secretion test without anesthesia, tear breakup time (BUT), the McMonnies questionnaire, the intraocular pressure (IOP), and the central corneal thickness (CCT) preoperatively and at1,3, and6, months postoperatively were used. Data were analyzed using paired-samples t test, chi-square test, non parametric test, correlation analysis, linear regression, and covariance analysis of general linear model. Results:87.7%of eyes were within±0.5D of the intended refractive target and98.8%of eyes were within±1.0D in SMILE group; the percentage of other groups were not significant different. At6months, the uncorrected visual acuity was≧20/20in83.6%of eyes,100%of eyes had a best-corrected visual acuity of≧20/20in SMILE group; the percentage of other groups were not significant different. Besides two eyes lost1Snellen lines in all groups, other eyes gained equal or even better BCVA. There was an increase in HO As, spherical aberration (SA) and coma aberration (CA) postoperatively. At1,3and6months, the value of HO As and S A in SMILE group were significantly lower than other groups (P<0.05). The log CS value without glare of6.3,4.0, and2.5degrees at1month decreased statistically significant but backed to preoperative levels after3months in SMILE group (P<0.05); so did the log CS value without glare of6.3,4.0,2.5, and1.6degrees in other groups.In all groups, there was no significant decrease in the results from the Schirmer secretion test without anesthesia after surgery. The value in the LASIK group was significantly lower than any other group at3and6months. In all groups, the BUT decreased significantly after surgery and did not return to preoperative levels within6months; the SMILE group time lasted significantly longer than the LASIK group at1month. The McMonnies score increased significantly in all groups after surgery but returned to preoperative levels within6months in all but the LASIK group. The mean McMonnies score in the SMILE group was significantly lower than other groups. The value of IOP and CCT were decreased postoperatively in all groups. The correlation analysis showed closely related (P<0.05). Linear regression equation could be concluded as:(the rate of IOP change)=c+k*(the rate of CCT change). A comparison was made between four regression lines, there were no significant difference among the test of slopes (Pk>0.05), but there were significant difference among the test of intercepts (Pc<0.05). The rate of IOP change was minimal in SMILE group and maximal in LASIK group. Four groups of patients were no serious intraoperative and postoperative complications during the follow-up period. Conclusion:SMILE, FS-LASIK, SBK and LASIK are stable, safe, effective and well-predictive for myopia and astigmatism. SMILE performs better visual quality, less dry eye, and better biomechanical stability.