The effect of oral ethanol consumption on eye movements in healthy volunteers.

Horizontal and vertical eye movements were recorded and analysed with an infrared photoelectric technique in 12 healthy volunteers under various blood alcohol concentrations (0.0, 0.5, 1.0 g/kg body weight, [% per thousand]). The predictive smooth-pursuit tracking and saccadic eye movements were studied in response to unpredictable target jumps and during scanning of a classical kitchen scene and a traffic scene. Smooth-pursuit eye movement gain value decreased dose-dependently and was compensated by an increased number of catch-up saccades. With increasing blood alcohol concentrations peak velocities of horizontal and vertical visually guided reflexive saccades decreased while their latencies to the target increased. At blood alcohol concentrations of 0.5% per thousand and 1.0% per thousand healthy volunteers showed significantly longer mean fixation durations and a lower total number of exploratory saccades when scanning both the classical kitchen scene and the traffic scene. Surprisingly, in both of these scanning tasks the total fixation duration or the relative number of exploratory saccades increased in those scene sectors in which exciting situations were presented. Additionally, the time interval needed to foveate these exciting areas for the first time increased, probably due to an attention deficit. In conclusion, these findings indicate that alcohol consumption impairs the velocity and initiation of saccadic and smooth-pursuit eye movements, but that subjects can nevertheless still recognize exciting and relevant areas of visual scenes. The significant increase in fixation time, however, does not allow scanning of the entire visual scene during an adequate period of time. Therefore the reduced visual exploration caused by alcohol reflects an impaired sensorimotor processing of active visual perception.