In this study, those who ingested caffeine appeared to have a faster reaction time and improved performance of DVA. Image courtesy of Getty Images. Click image to enlarge.
As you no doubt know from your morning coffee or tea, caffeine can give your brain a boost. In addition to improved cognition, acute caffeine ingestion has also been associated with improved visual function. Researchers analyzed this widely consumed psychostimulant’s effects on dynamic visual acuity (DVA) and reported that it seems to have an ergogenic effect.
DVA is defined as the ability to resolve fine details when there’s relative motion between the target and the observer. It’s important for real-world scenarios like ball sports, driving and piloting. This cognitive process is complex and highly sensitive to external factors such as diurnal variations, level of expertise, sleep deprivation and psychostimulants.
“Caffeine in particular is known to increase the velocity of rapid eye movements,” the researchers explained in their paper. They noted that caffeine may also have an effect on contrast sensitivity, ocular aberrations and accommodation. “In addition, the ingestion of caffeine has been shown to enhance visual processing, facilitating the detection of visual stimuli and response preparation.”
The placebo-controlled, double-blind crossover study was the first of its kind to measure acute caffeine effects on DVA. It included 21 low-caffeine consumers (average age 22.5 years). On two different days and in a random order, each participant ingested either caffeine (4mg/kg) or placebo. Their DVA was measured after 60 minutes of ingesting the capsule.
The researchers found significantly greater accuracy for both the horizontal and random motion paths of DVA after caffeine ingestion. Caffeine intake was also associated with a faster reaction time for horizontally but not randomly moving targets. Study participants reported significantly higher levels of perceived activation after consuming caffeine in comparison with placebo.
“Caffeine is a central nervous stimulant that acts as an adenosine receptor antagonist,” the researchers explained. “Our results showed that caffeine consumption increased subjective levels of activation, which agrees with many studies that provide that caffeine enhances alertness and feelings of wakefulness and energy.”
Other studies have reported improved accuracy and response speeds after caffeine ingestion. “In the same line, we observed that caffeine reduced the time used to detect the moving objects in the DVA test. The faster reaction times observed under the effects of caffeine could be explained by the positive influence of caffeine on stimulus processing and decision-making. However, we just observed this effect (faster reaction time after caffeine intake) for horizontally moving targets, but not with the random motion path, which could be due to the shorter presentation time of the horizontal targets.”
DVA depends on target velocity. The faster the target speeds, the worse the reaction times, for both caffeine and placebo. “Interestingly, our results showed that participants correctly identified smaller moving stimuli after caffeine ingestion compared with ingestion of the placebo,” the investigators noted. “This finding was observed for both horizontally and randomly moving targets, which suggests that caffeine ingestion improved DVA.” They added that eye movement and contrast sensitivity, which are implicated in DVA performance, are also sensitive to caffeine.
From their findings, the researchers concluded that caffeine ingestion improves DVA performance. “The ingestion of caffeine could be recommended in tasks that have demanding attentional requirements and/or tasks that require good resolution of moving targets such as driving or dynamic sports.” Importantly, however, the behavioral response to caffeine depends on habitual intake. The researchers said it’s likely that the effect of caffeine on DVA was more pronounced in this experimental sample.
Redondo E, Jiménez R, Molina R, et al. Effects of caffeine ingestion on dynamic visual acuity: a placebo-controlled, double-blind, balanced-crossover study in low caffeine consumers. Psychopharmacology. August 22, 2021. [Epub ahead of print].