Clinical Study On Characteristics Changes Of Ocular High-order Aberrations And Corneal Biomechanical Properties After SMILE

ObjectiveTo investigate and analyze the characteristical changes before and after Small incision lenticule extraction and Femtosecond laser in situ keratomileusis by the Wavefront Analysis Comparison. For the second part, evaluate and compare corneal biomechanical properties between eyes treated with microincision lenticule extraction(MILE) and small incision lenticule extraction(SMILE) surgery.MethodsA prospective study. The trial group had 34 patients( 16 men, 18 women)underwent with SMILE, and 28 cases(15 men, 13 women) with FS-LASIK as the control group, aged 18 to 39 years and the right eye only was selected to be analyzed each patient. All patients need to take the conventional examination and pentacam preopration, and the ocular higher order aberrations were measured with the Hartman-Shack wavefront analyzer, at preoperation, 1 month and 3 month postoperation. In the second part there were 124 eyes of 62 patients received the refractive surgery, 60 eyes received MILE procedure with 2 mm incision, 64 eyes received SMILE procedure with 3~5 mm incision. The main outcome measurements were Corneal hysteresis(CH), corneal resistance factor(CRF), and 37 other biomechanical waveform parameters assessed by an Ocular Response Analyzer at 1week, 1 and 6 months postoperatively. The paired t test, independent t test and pearson correlation analysis were used to investigate and analyze the data collected.Results1. At the 1rd month postoperation of SMILE group,C3-1、C33were higher than the FS-LASIK group(t=-2.844,2.389,p<0.05), for FS-LASIK group Sh、S4、S5、S6 、C40were higher than the SMILE group(t=-3.617,-3.398,-3.577,-5.511,-2.079,p<0.05).2. At the 3rd month postoperation of SMILE group, C3-1、C33were higher than the FS-LASIK group(t=-2.247,2.118,p<0.05), for FS-LASIK group Sh、S3、S4、S5、S6、C40were higher than the SMILE group(t=-3.984,-2.018,-3.543,-2.180,-4.621,-3.228, p<0.05).3. For the correlation analysis, at the 1rd month postoperation of FS-LASIK group, Sh、S4、C40had negative relationship with the level of myopic correction preoperation attempted(r=-0.431,-0.404,-0.426,p<0.05), and at the 3rd month Sh had negative relationship with the myopic correction level preoperation still(r=-0.385,p<0.05), no other correlation was found between others(p>0.05).4. In the corneal biomechanics part, both CH and CRF values decreased after MILE and SMILE(p=0.000).5. The ΔCRF, ΔCH index(ΔCH/preoperative CH) and ΔCRF(ΔCRF/preoperative CRF) index were statistically smaller in MILE group than in SMILE group(t=-2.446,-2.611,-2.475, p=0.016, 0.010, 0.015) at 1 week postoperatively.6. The ΔCH index at 1 month after MILE surgery were found to be statistically smaller than after SMILE(t=-2.603, p=0.010).7. Significant correlations were shown between MRSE, LT, RST index andΔCRF index, ΔCH index(p<0.005).Conclusions1.SMILE showed good optical quality at the early stage post-operation,compared with FS-LASIK it caused smaller change of ocular higher aberration, but each of them has its own particularity. Maybe it was associated with the surgical flap-making procedure and corneal wound healing after surgery.2. For the FS-LASIK group, the higher level of myopic diopter were corrected the greater Sh、S4、C40would be, but over time the relationship becomes not that obvious, maybe it was associated with corneal wound healing.3. Both MILE and SMILE procedures can affect the biomechanical properties of the cornea.4. MILE causes less corneal biomechanical change than SMILE procedure which may means a less invasive procedure.