EFFECT OF ALCOHOL AND MARIHUANA ON EYE-MOVEMENTS

Abstract

The effects of alcohol and marijuana (tetrahydrocannabinol, THC) on saccades, smooth pursuit, and optokinetic nystagmus were quantitatively evaluated in 24 normal subjects using electrooculographic recordings. Each subject was given an initial trial run and then tested 3 times (at weekly intervals) with either 0.0 .mu.g THC or 100 .mu.g THC/kg bodyweight while at 3 different blood alcohol concentrations (0.0, 0.05 and 0.1%). A 2 .times. 3 factorial design was used. Saccades and smooth persuit were induced by a dot of light moving in steps and ramps on a modified television set. Optokinetic nystagmus was induced by a cloth drum completely surrounding the subject and moving at a constant velocity of 30.degree./s. Alcohol (0.05 and 0.1%) alone produced significant (P < 0.05) impairment of saccade maximum velocity and reaction time, smooth pursuit velocity, and optokinetic slow-component velocity. The addition of THC caused performance to further deteriorate at each blood alcohol level but, in all but 1 instance, the added effect was not statistically significant (P < 0.05). At the THC and alcohol concentrations used in this study, the eye movement effects of alcohol over-shadowed those of marijuana.