Older adults’ visual functions— eye movement reaction time, speed, and accuracy—are acutely impaired by alcohol, and those with chronic alcohol use disorder (AUD) are not immune to these impairments when imbibing. The study in Alcohol: Clinical & Experimental Research is the first to examine alcohol’s acute effects on eye movements, pupil size, and self-perception of impairment in middle-aged to older adults with AUD versus a control group of those with lifetime light drinking. Alcohol disrupts eye movement and pupil dilation, resulting in delayed visual reactions and reduced accuracy. Many believe that those with longer-term excessive drinking have built up tolerance and are protected against eye movement impairment. While this study showed that older drinkers with chronic AUD (vs. light drinkers) had less impairment in visually tracking an object that moves predictably, they were equally impaired in eye movements that require quick adjustments to randomly appearing objects. The persons with AUD also reported that they were less impaired than the light drinkers. Thus, habitual excessive drinkers may develop tolerance to some alcohol-related effects. However, they were unable to overcome poor reactions to unpredictable stimuli and were less able to recognize their impairment, which could lead to false confidence in their ability to drive or perform tasks when intoxicated.
Researchers in Chicago conducted a placebo-controlled, double-blinded laboratory study involving 117 adults aged 40–65. The participants filled out surveys on their health and lifetime use of alcohol, as well as a validated alcohol use assessment and AUD screening tests. Sixty-two were light drinkers (1-9 drinks a week, with occasional binge drinking), and 55 had chronic AUD (they averaged 40 drinks a drink and about 25 years of AUD). The participants attended two sessions in which they undertook baseline assessments, including eye tracking tests, and then consumed either an alcoholic drink or a placebo drink. After 30 minutes and again at 3 hours, they filled out surveys on how impaired they thought they were and then repeated eye tracking. Using a high-resolution camera synced with a computer and display, eye tracking tests captured pupil size, smooth pursuit (watching a predictable target move back and forth horizontally), and saccade eye movements (quick, unconscious movements toward or away from randomly appearing targets).
Pupils dilated more after drinking alcohol than the placebo in both drinking groups. After consuming alcohol, the AUD drinkers were less affected than the light drinkers in the smooth pursuit visual tasks. Yet both groups were similarly impaired on the saccade measures, demonstrating delayed response, slower velocity, and reduced accuracy to targets that appeared randomly on the screen. (This difference between smooth pursuit and saccade outcomes may be related to the neurobiology of those eye movements and their underlying neuroplasticity.) Self-perceptions of alcohol impairment correlated more strongly with smooth pursuit than saccade, perhaps because smooth pursuit is a more conscious activity than saccadic movements. The light drinkers, however, were more aware of their impairment while intoxicated than the AUD drinkers were, adding to evidence that people with chronic AUD may falsely believe they can perform well while intoxicated.
In sum, chronic drinkers’ are susceptible to eye movement impairment while intoxicated, and this may manifest in slower and less accurate reactions to environmental signals. Combined with a reduced perception of impairment, such individuals may also overestimate their ability to deflect or dodge dangerous objects while driving or engaging in tasks. Alcohol-induced impairment – as well as poor perception of it – likely explain the high rates of alcohol-related injury in people who drink excessively. This finding aligns with a previous study involving younger drinkers, which similarly showed people with AUD were sensitive to certain alcohol-induced impairments yet less aware of those effects.
The eyes have it: Alcohol-induced eye movement impairment and perceived impairment in older adults with and without alcohol use disorder. N. Didier, D. Cao, A. King.
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