Coffee being poured Coffee pot pouring cup of coffee. copyright American Heart Association

Effects of Caffeine on Reaction Times and Visual Acuity Tasks Interview with:

Kristine Dalton PhD FAAO, FBCLA School of Optometry & Vision Science University of Waterloo Waterloo, Canada

Dr. Dalton

Kristine Dalton PhD FAAO, FBCLA
School of Optometry & Vision Science
University of Waterloo
Waterloo, Canada What is the background for this study?

Response: Dynamic visual acuity refers to the ability to detect and perceive small details in objects that are moving relative to an observer.  Dynamic visual acuity is a complex visual function, that involves a number of different aspects of vision, including detecting the target, moving the eyes appropriately to observe the target, and processing the visual information from the target in the brain to interpret what we are seeing.   What makes dynamic visual acuity so interesting to study, is that as a visual function, it appears to play an important role in a number of real-world situations, including playing sports, driving, and piloting, and it may provide us more information about how the visual system is functioning compared to the more traditional, static vision tests alone.

Previous research has demonstrated that consumption of caffeine has been shown to benefit physiological, psychomotor, and cognitive performance.  More recently there has been an increased interest in studying the impacts of caffeine on the vision system, however the impact of caffeine on dynamic visual acuity has not been studied.  This study was designed to address this limitation in the literature, particularly because dynamic visual acuity appears to be such an important visual function for real-world activities. What are the main findings? How much caffeine/coffee is required to demonstrate this effect? 

Response: The main findings were that caffeine improved participants’ reaction times and their ability to detect small details from moving objects.  Participants in this study, were young, healthy, habitual low caffeine consumers (<2 cups of coffee per day on average), and we saw the positive effects on reaction time and dynamic visual acuity after participants ingested the equivalent of two espressos worth of caffeine. What should readers take away from your report?

Response: This research demonstrates that consumption of caffeine, at least in smaller doses, appears to improve our ability to see and respond to moving objects. What recommendations do you have for future research as a result of this work?

Response: Future research will need to focus on understanding how caffeine improves performance on the dynamic visual acuity task, as we do not know if the improvement in performance is being driven by improvements in eye movements, improvements in visual processing by the brain, or improvements in both areas. Additionally, future research should explore whether or not caffeine has a similar effect on vision in habitual high-caffeine consumers. Is there anything else you would like to add?

Response: If we can understand how caffeine improved performance on the dynamic visual acuity task, then we may also be able to develop novel ways to train and improve dynamic visual skills in individuals.  In turn, improving dynamic visual skills through training could enhance performance on everyday tasks, such as driving.

My disclosures:

The dynamic visual acuity test used in this study was developed in my lab at the University of Waterloo, Canada.  The study itself was designed and conducted by my colleagues at the University of Granada, Spain.


Redondo, B., 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 2383391–3398 (2021). 



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Last Updated on December 4, 2021 by Marie Benz MD FAAD