Objective: To study the influence of three different corneal refractive surgeries on corneal biomechanics.Methods: Sixty-four patients (125 eyes) were enrolled in this prospective case series study during February2016 to April 2016. Fifty-five eyes underwent femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK), 47 eyes underwent sub-Bowman’s keratomileusis (SBK) and 23 eyes underwent laser epithelial keratomileusis (LASEK). AT1, Vout, HC-radius, DA, IOP, and CCT were obtained with a Corvis ST 1 day, 1 week, and 3 months postoperatively. One way ANOVA, Pearson, correlation, paired t test were used to analyze data. Results: The biomechanical parameters in the FS-LASIK group were significantly correlated with CCT (AT1: r=0.455, P<0.001; Vout: r=-0.286, P=0.034; HC-radius: r=0.357, P=0.007; DA: r=-0.341, P=0.011; IOP: r=0.436, P=0.001), with RST (AT1: r=0.563, P<0.001; Vout: r=-0.417, P=0.007;HC-radius: r=0.552, P<0.001; DA: r=-0.395, P=0.012; IOP: r=0.516, P<0.001) and with AD (AT1:r=-0.721, P<0.001; Vout: r=0.466, P=0.002; HC-radius: r=-0.407, P=0.009; DA: r=0.596, P<0.001; IOP:r=-0.612, P<0.001). The biomechanical parameters in the SBK group were strongly correlated with CCT(AT1: r=0.364, P=0.012; Vout: r=0.408, P=0.004; HC-radius: r=0.326, P=0.025; DA: r=-0.362, P=0.012;IOP: r=0.387, P=0.007). For LASEK, only AT1 (r=0.625, P=0.001), IOP (r=0.624, P=0.001) correlated with CCT. For the 3 groups, AT1, HC-radius, IOP and CCT decreased compared with preoperative values; Vout and DA increased compared with preoperative values (AT1: F=7.313, P=0.001; IOP: F=4.979, P=0.009).The values of AT1 and IOP in the FS-LASIK group were significantly greater than those in the LASEK group. Vout and DA were significantly lower than the values in the LASEK group at 1 week after surgery (Vout:F=3.420, P=0.038; DA: F=9.024, P<0.001). The values of the SBK group were moderate and between the two other groups and compared with the FS-LASIK group difference was not statistically significant.There were no significant differences between the three groups three months after surgery. Conclusions:All three procedures are safe and reliable for the treatment of myopia at a sufficient corneal thickness. For FS-LASIK, biomechanical stability is restored faster after surgery because of the accuracy and superiority of femtosecond laser cutting. LASEK biomechanical changes and residual matrix bed thickness and depth
have a low correlation in patients with severe myopia when the cornea is relatively thin.