AIM: To investigate the characteristics of optical modulation transfer function(MTF)of the eyes after femtosecond laser small incision lenticule extraction(SMILE), and to evaluate the relationship between visual acuity(VA), contrast sensitivity(CSF)and MTF.

METHODS: From June to November, 2015, 34 myopia patients(68 eyes)who underwent SMILE surgery in Tianjin Eye Hospital were selected in cross-section. The postoperative eye condition was stable for more than 3mo after surgery. The residual diopter of the eyes after SMILE was less than ±0.50D. Under bright vision, measured VA by International standard visual acuity chart and CSF by CSV-1000E. The wavefront aberration of the whole eyes were measured by WaveScan, and MTF of the eyes were obtained by using aberration formula conversion and Matlab programming. The MTF of(3, 6, 12, 18)c/d frequency region were counted.

RESULTS: CSF values in 3, 6, 12, 18 c/d frequency range were 63.19±3.18, 110.25±5.22, 57.65±3.76, 16.15±1.04; MTF values in 3, 6, 12, 18 c/d frequency range were 0.80±0.02, 0.56±0.03, 0.30±0.02, 0.19±0.02. In 6, 12, 18 c/d frequency range, visual acuity was significantly correlated with CSF(r=0.548, 0.337, 0.324, P<0.01,=0.005, 0.007). In 18c/d frequency range, CSF was significantly correlated with MTF(r=0.241, P=0.048).

CONCLUSION: The change of optical quality(MTF)after SMILE was different from that of visual quality(visual acuity and contrast sensitivity). Although the aberration of refractive system changed, the SMILE surgery had no effect on CSF, which indicated that neuro-brain had a compensatory effect on visual quality. Computational MTF has certain theoretical and clinical value in evaluating the optical quality after refractive surgery.