AIM: To evaluate the changes of human eyes optical and visual quality after LASIK through modulation transfer function(MTF)measurement and contrast sensitivity function(CSF)measurement.

METHODS:It was a prospective cohort study. Forty-seven patients(92 eyes)were divided into low myopia(-2.28±0.48D), moderate myopia(-4.54±0.97D)and high myopia(-6.86±1.17D)groups according to the spherical equivalent(SE)diopter before the surgery. The uncorrected visual acuity(UCVA), best-corrected visual acuity(BCVA), SE diopter, wavefront aberration, CSF measurement, PSF measurement were examined before and after operation. The follow up visits of the patients were scheduled at the 7^th day, 1^st and 3^rd month. CSF curves, which were obtained with Carl Zeiss WASCA Analyzer wavefront aberration instrument under the 3.0mm and 5.0mm pupil size conditions, were scanned and loaded into Engauge Digitizer 4.1 digital software to obtain PSF data of certain space frequency. And CSF data were obtained with Optical 6500 of STEREO OPTICAL Company under day and night environment. The data were statistical analyzed with paired-t test.

RESULTS: CSF data declined obviously compared with the preoperative data in early stage(7 days)after surgeries. Partial low space frequency CSF data(low space frequency CSF data in 3.0mm pupil size condition and moderate myopia patients' low space frequency CSF data in 5.0mm pupil size condition)recovered back to preoperative levels in 3 months after LASIK. The myopic degree was higher, the CSF values of moderate and high spatial frequency were harder to restore to preoperative levels. Most of the MTF values declined in 1 week after LASIK. MTF values approximately recovered back to preoperative levels in 1 month-3 months after LASIK. Partial MTF values of 1 week after LASIK had no statistical differences compared to the preoperative data.

CONCLUSION: MTF values approximately recover back to preoperative levels earlier than CSF values. All the MTF values recover back to preoperative levels in 3 months after LASIK, but partial space frequency CSF values not. MTF values reflect the improvement of visual quality in early stage after LASIK. MTF data obtained with Carl Zeiss WASCA Analyzer wavefront aberration analyzer comprehensively and objectively reflect the optical system changes in early stage after LASIK.