Objective To test the effects of altitude hypoxia on visual function after laser in situ keratomileusis (LASIK) and to evaluate flight adaptability after laser refractive surgery.Methods This was a self-control designed study.Forth eyes of 20 healthy males with a mean age of 23.8±1.2 years volunteered for this prospective study.All patients had bilateral LASIK surgery 1 year prior to the study.Interocular pressure,near stereopsis,color vision,refractive error,contrast sensitivity (CS) (photopic,scotopic+glare environments; 3,6,12,18 c/d spatial frequencies) were measured before exposure to the hypobaric chamber.The atmosphere in the chamber ascended to an equivalent of a 5 000 m altitude at the rate of 30 m/s.Subjects were measured again after remaining there for 10 minutes without an oxygen supply.The chamber then returned to ground level at the rate of 10-15 m/s.Data were analyzed using a paired t test.Results There were no significant differences in intraocular pressure or spherical equivalent refractive error for either eye before and after the hypobaric experiment:right eyes:13.0±1.7 mmHg vs.13.0±2.1 mmHg,t=-0.56,P＞0.05,-0.90±0.61 D vs.-1.08±0.75 D,t=1.71,P＞0.05; left eyes:13.0±2.0 mmHg vs.13.0±2.0 mmHg,t=-0.81,P＞0.05;-1.21±0.61 D vs.-1.06±0.54 D,t=-1.33,P＞0.05).Near stereopsis (21.5±2.4 vs.27.6±8.3,t=-3.39,P＜0.05) and color vision (9.60±2.73 vs.27.20±8.57,t=-2.81,P＜0.05) were depressed.Contrast sensitivity was depressed only at 18 cycles/degree in the scotopic+glare environment.Conclusion Based on this study,we conclude that hypoxia has little effect on interocular pressure,refractive error or CS except at 18 c/d in the scotopic+glare environment after LASIK surgery.Near stereopsis,color vision and CS at 18 c/d in the scotopic+glare environment were reduced.