['To investigate whether ethanol administration disturbs the tear film and ocular surface.', 'Case-control study.', 'Twenty healthy male subjects were recruited. Ethanol was administered to 10 subjects and another 10 subjects served as controls.', 'Twenty healthy male subjects with no ocular disease were recruited. Ethanol (0.75 g/kg) was administered orally at 8 pm for 2 hours to 10 subjects.', "The tear film and ocular surface were evaluated at 6 pm before drinking, at midnight, and immediately (6 am) and 2 hours (8 am) after waking the next morning. Tear osmolarity, ethanol concentration in tears and serum, Schirmer's test results, tear film break-up time (TBUT), corneal punctuate erosion, and corneal sensitivity were measured.", "Ethanol was detected in tears and serum at midnight, but it was not detected the next morning. The mean tear osmolarity level increased in the alcohol group at midnight compared with that in the control group (P<0.001). The alcohol group showed a significantly shorter TBUT compared with the control group after drinking alcohol (P<0.001 at 12 am, P<0.001 at 6 am, and P = 0.002 at 8 am). There were significantly higher fluorescein staining scores in the alcohol group compared with those in the control group at 6 am and 8 am (P = 0.001 and P<0.001, respectively). No significant change was shown in corneal sensitivity or Schirmer's test results in either group."] Does oral alcohol administration disturb tear film and ocular surface?