AIM: To compare the corneal biomechanical changes at early stage after femtosecond laser assisted in situ keratomi(LASIK)and microkeratome LASIK according to different residual corneal stroma thickness/cornea thickness(RCST/CT).

METHODS: Ninety-four patients(187 eyes)with femtosecond LASIK(FS-IK)and 96 patients(192 eyes)with microkeratome LASIK(M-IK)were included in this study. LASIK group was divided into three groups according to the ratio of RCST/CT, which were IK-I group(RCST/CT<55%), IK-Ⅱ group(55%≤RCST/CT<60%)and IK-Ⅲ group(RCST/CT≥60%). Corneal hysteresis(CH)and corneal resistance factor(CRF)were measured by reichert ocular response analyzer(ORA)at pre-operation, postoperative 1and 3mo.

RESULTS: Compared with FS-IK and M-IK,there were no statistical difference in CH and CRF(F=0.44, F=2.56, P=0.51, P=0.11). Based on different RCST/CT, there were statistical differences in CH and CRF between group Ⅰ and group Ⅱ(F=103.03, 128.48,P<0.05), group Ⅱ and group Ⅲ(P<0.05), group Ⅰ and group Ⅲ(P<0.05). There were statistical differences in CH and CRF between pre-operation and different postoperative times(F=576.99, 1162.06, P<0.05). CH and CRF of postoperative 1mo and 3mo were significantly smaller than pre-operation(P<0.05), but there was no statistical difference between postoperative 1and 3mo(P>0.05).

CONCLUSION: The biomechanical parameters decreased at early stage after femtosecond LASIK and microkeratome LASIK, but there is no statistical difference between femtosecond LASIK and microkeratome LASIK. The less the ratio of RCST/CT, the more effect on biomechanics.