Objective Discuss the effect of luminance on cyclotorsion and pupil center during Laser in situ keratomileusis (LASIK). Methods Prospective case series study. One hundred and forty subjects (268 eyes) were selected to receive LASIK operation. During the operation, the brightness of laser lighter was adjusted, rotation angle of eyeballs, diameter and position of pupil centre under high brightness and low brightness was tested using Visx S4 IR examer laser chi-square test and independent samples t test was used. Results Two hundred and fifty-nine eyes (96.6%) rotated, and mainly (69.5%) was extorsion after brightness adjusted. Furthermore, direction-changing occurred in 26 eyes. The rotation angle in most eyes (247 eyes, counted 95.4%) were within 2°. Under the high brightness and dark brightness, pupil centre of most eyes shifting naso-upside, but the discrepancy under different brightness with no statistic difference. Conclusion During LASIK procedures, luminance brightness will cause cyclotorsion and position shifting of pupil centre, therefore, brightness will affect the accuracy of LASIK.