AIM:To investigate the changes of corneal biomechanics after Femto LDV laser flapping in laser in situ keratomileusis(LASIK).

METHODS: Preoperatively, 3 months, 6 months after LASIK, 93 myopia patients(186 eyes)in flapping procedure by Femto LDV laser were examined by Ocular response analyzer(ORA). The central corneal thickness(CCT)was also measured by ultrasonic pachymetry. Parameters were compared between postoperative(3 months)and preoperative, postoperative(6 months). Comparisons included the corneal thickness and corneal compensated intraocular pressure(Iopcc), Goldmann correlated IOP value(Iopg), corneal resistance factor(CRF), corneal hysteresis(CH).

RESULTS:The CCT(447.61±39.57μm)were significantly changed comparing with preoperative(539.88±29.72μm)(t=-47.223; P=0.000). The CCT of 6 months postoperative(448.78±39.19μm)was slightly thicker than that of 3 months'(t=2.15,P=0.033). Iopcc, Iopg of 3 months after LASIK(13.75±2.13, 9.54±2.35)mmHg were significantly changed comparing with preoperative(16.29±2.88, 15.09±3.29 )mmHg(t=-13.604, -23.594; P=0.000, 0.000). The difference was(2.55±2.25, 5.55±3.21)mmHg. There were no significant changes between Iopcc, Iopg of 6 months(13.61±1.96,9.32±2.07)mmHg and that of 3 months after LASIK. CRF and CH of 3 months after LASIK(6.36±1.45,7.71±1.30)mmHg were significantly changed comparing with preoperative's(9.84±1.99,9.77±1.56)mmHg(t=-24.116, -19.171; P=0.000, 0.000). The difference was(3.49±1.97, 2.06±1.47)mmHg. There were no statistical differences between 6 months(6.24±1.38, 7.67±1.25)mmHg and 3 months(t=1.456, 0.636; P=0.147, 0.525).

CONCLUSION: The corneal biomechanical properties after FS- LASIK are lower than that of preoperative. Corneal biomechanics sustains steadily about 3 months after LASIK.