PURPOSE. To investigate prospectively the relation between induced changes in higher- order aberrations of the eye and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS. In 200 eyes of 110 consecutive patients (mean age, 32.7 ± .8.4 years) undergoing LASIK, ocular aberrations and contrast sensitivity function were determined before and 1 month after surgery. The amount of myopic correction was 5.2 ± .2.8 D (range, 1.0- 13.0). Ocular higher- order aberrations were measured for a 4- mm pupil using the Hartmann- Shack wavefront analyzer (KR- 9000PW; Topcon, Tokyo, Japan). The root mean square (RMS) of the third- and fourth- order Zernike coefficients was used to represent coma- and spherical- like aberrations, respectively. Total higher- order aberrations were calculated as the RMS of the third- and fourth- order coefficients. Contrast sensitivity and low- cont- rast visual acuity were measured. From the contrast sensitivity data, the area under the log contrast sensitivity function (AULCSF) was calculated. RESULTS. LASIK significantly improved logMAR best corrected visual acuity (Wilcoxon signed- rank test, P < .0.001), but significantly reduced AULCSF (P < 0.001) and low- contrast visual acuity (P=0.007). Total higher- order (P < 0.001), coma- like (P < 0.001), and spherical- like (P < .0.001) aberrations were significantly increased after LASIK. The greater the amount of achieved myopia correction was, the more the changes in contrast sensitivity function and ocular higher- order aberrations were. The induced changes in AULCSF by LASIK showed significant correlations with changes in total higher- order (Pearson r=- 0.221, P=0.003), coma- like (r=- 0.205, P=0.006), and spherical- like (r=- 0.171, P=0.022) aberrations. The changes in logMAR low- contrast visual acuity by surgery significantly correlated with changes in total higher- order (r=0.222 , P=0.003), comalike (r=0.201 , P=0.007), and spherical- like (r=0.207, P=0.005) aberrations. CONCLUSIONS. Conventional LASIK significantly increases ocular higher- order aberrations, which compromise the postoperative contrast sensitivity function. PURPOSE. To investigate prospectively the relation between induced changes in higher-order aberrations of the eye and changes in contrast sensitivity by conventional laser in situ keratomileusis (LASIK) for myopia. METHODS. In 200 eyes of 110 consecutive patients (mean age, 32.7 ± .8.4 years) undergoing LASIK, ocular aberrations and contrast sensitivity function were determined before and 1 month after surgery. The amount of myopic correction was 5.2 ± .2.8 D (range, 1.0- 13.0). Ocular higher order aberrations were measured for a The root mean square (RMS) of the third- and fourth-order Zernike coefficients was used to represent coma- and spherical-like aberrations, respectively. Total higher- order aberrations were calculated as the RMS of the third- and fourth-order coefficients. Contrast sensitivity and low- cont rast visual acuity were measured. From the contrast sensitivity data, t LASIK significantly improved MARD best corrected visual acuity (Wilcoxon signed-rank test, P <.001), but significantly reduced AULCSF (P <0.001) and low-contrast Total higher-order (P <0.001), coma-like (P <0.001), and spherical-like (P <.0.001) aberrations were significantly increased after LASIK. The greater the amount of achieved myopia correction was, the more changes in contrast sensitivity function and ocular higher-order aberrations were. The induced changes in AULCSF by LASIK showed significant correlations with changes in total higher- order (Pearson r = - 0.221, P = 0.003), coma - like (r = - 0.205, P = 0.006), and spherical- like (r = - 0.171, P = 0.022) aberrations. The changes in logMAR low- contrast visual acuity by surgery significantly correlated with changes in total higher- order ( r = 0.222, P = 0.003), comalike (r = 0.201, P = 0.007), and spherical- like 0.207, P = 0.005) aberrations. CONCLUSIONS. Conventional LASIK indicators increase ocular higher order aberrations, which compromise the postoperative contrast sensitivity function.