On determining the relationship between blood alcohol concentration and smooth pursuit eye movements

Residual impairment after alcohol consumption implies that the relationship between blood alcohol concentration (BAC) and deficits in performance of s ome task is not the same when becoming intoxicated as it is when returning to sobriety. A pilot study was performed to determine the feasibility of an d the appropriate methodology for studies on residual impairment of smooth pursuit performance. Four subjects consumed alcohol for 2 h. Measurements o f BAC and smooth pursuit eye movements were made every 30 min during drinki ng and for 4 h after drinking. Pursuits were elicited by having subjects tr ack a sinusoidal target (0.40 Hz and 0.60 Hz) for 10 s. Impairment of smoot h pursuit was quantified with Frequency analysis scores. Frequency analysis scores declined as BAC increased. As BAC decreased, frequency analysis sco res tended to increase toward pre-drink levels. The relationship between BA C and frequency analysis score was not significantly different on the ascen ding and descending limbs of the blood alcohol curve. However, the idea tha t residual impairment does not occur could not be conclusively demonstrated for several reasons. First, as BAC returned to pre-drink levels, frequency analysis scores were inconsistent for each subject perhaps because of bore dom and fatigue. Second, the relationship between BAC and frequency analysi s score varied between subjects. Finally, because the recording periods wer e short, the effect of alcohol on sustained attention could not be assessed , in this paper, potential artifacts in studies of residual impairment of p ursuits are discussed and potential solutions to the methodological problem s encountered in the pilot study are provided.