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Minjie Chen, jinhui dai; Comparison of biomechanical effects of small incision lenticule extraction and laser-assisted subepithelial keratomileusis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3925.
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To compare the biomechanical properties of the cornea after small-incision lenticule extraction (SMILE group) with those after laser-assisted subepithelial keratomileusis (LASEK group) by Ocular Response Analyser.
In this prospective study, eyes that had mild to moderate myopic laser refractive surgery were categorized according to the type of flap creation: SMILE (n=31) or no flap creation LASEK (n=31). Corneal hysteresis (CH) and the corneal resistance factor (CRF) parameters were quantitatively assessed with the Ocular Response Analyzer preoperatively and 1, 3 months postoperatively. Multiple linear regression model analysis was then applied to adjust for selected covariates (the planned ablation depth, preoperative CH and CRF) to control for potentially confounding factors.
There were no significant differences in the preoperative manifest refraction spherical equivalent (MRSE), central corneal thickness (CCT), CH or CRF values between the LASEK group and the SMILE group (P>0.05). However, the planned ablation depth (AD) was 91.93±2.34um in the SMILE group which was significantly more than 80.37±2.78um in the LASEK group (P=0.0020). The decrease in CH and the CRF was statistically significant 1 and 3 month postoperatively compared with preoperatively in both groups (P<.0001). The LASEK group had significantly lower postoperative CH and CRF values than the SMILE group at both follow-ups after adjustment for the planned AD (P<0.1). Also, the changes in CH and CRF were less after SMILE than after LASEK in the 3-month postoperatively (P=0.002 and P=0.058, respectively). No significant correlations were found between the planned AD and changes in CH or CRF at any points in both groups.
CH and CRF decreased after SMILE and LASEK. However, changes in the cornea’s viscoelastic properties were less after SMILE than after LASEK. Consequently, SMILE should be able to correct higher levels of myopia.
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