AIM:To evaluate far contrast sensitivity function before and after myopic laser in situ keratomileusis(LASIK).METHODS:With test chart,far contrast sensitivity was measured in randomly selected 58 subjects 112 eyes before,1 month and 3 months after LASIK.The patients were assigned to three different groups according to the mean spherical equivalent.Mean spherical equivalent of low/moderate myopia group was under-6.00D,average(-4.22±1.24)DS,mean spherical equivalent of high myopia group was-6.00--9.00 D,average(-6.98±1.42)DS,and mean spherical equivalent of superhigh myopia group was over-9.00 D,average(-10.88±1.36)DS.The contrast sensitivity was measured at 1.5,3.0,6.0,12.0 and 18.0 cycles per degree(c/d)spatial frequency respectively and comparison was made in them.RESULTS:There was a general reduction in far contrast sensitivity of superhigh myopia in all spatial frequencies at postoperative 1 month compared with the preoperative contrast sensitivity.The group(<6.00D)preoperative and postoperative contrast sensitivity did not differ at 1 month in all spatial frequency.Descendent rates of far contrast sensitivity in superhigh myopia group were larger than that in low/moderate myopia group at 3.0,12.0c/d(P<0.01),and that in superhigh myopia group were larger than that of in high myopia group at 18.0c/d(P<0.01).There were no siginificant difference between three groups three months after LASIK(P>0.05),and far contrast sensitivity was near preoperational level.CONCLUSION:One month after LASIK,the higher myopia has obvious decrease of far contrast sensitivity.