By James M. Stringham, PhD
When someone hears the term “visual performance,” they typically think of visual acuity—and why wouldn’t they? Visual acuity is obtained at every visit to the eye clinic, and everyone knows that 20/20 constitutes “good vision.” But visual performance is actually a collection of several abilities, only one of which is acuity. In fact, the two most important jobs of the visual system are to detect changes in illumination across space (contrast) and time (motion); strictly speaking, these have little to do with acuity.
Whereas most eyecare practitioners are somewhat familiar with contrast sensitivity, very few appreciate the contribution to visual performance of temporal processing speed. You might be surprised to learn that among normal, healthy patients, visual processing speed is quite variable. Given a basic critical flicker fusion (CFF) threshold task, young adults aged 18 to 25 range from 17 to 35 Hz (and sometimes higher) for complete fusion of the disk of light! This range of processing speed is found in all age groups, albeit shifted downward with increasing age.
Accounting for the Wide Range
Studies in my lab and others have found a strong relation between levels of the macular carotenoids (lutein, zeaxanthin, and meso-zeaxanthin) deposited in the retina as macular pigment and visual processing speed. In cross-section, these are strong correlations. Upon supplementation with the macular carotenoids, significant increases in CFF can be seen in as few as three months. The effect is linearly related to macular pigment density—the higher you go in the eye; the faster processing speed becomes.
Processing Speed in Competition
Several studies have demonstrated that increases in processing speed yield faster reaction times, more accurate prediction of events, and result in better anticipation/decision making. In terms of everyday life, these improvements would help significantly with tasks that involve fast-moving objects (for example, driving). But faster processing speed is also beneficial in competitive sports.
In nearly every sport, precise timing, fast reaction time, anticipation, and accurate prediction—all shown to improve with high macular carotenoid status—are rewarded with success. Considering that roughly a third of Americans participate in sports, increasing their macular pigment density would not only will improve their vision for everyday tasks, but also increase their chances for success on the court…or field, or wherever they’re competing.
Knowledge of these kinds of performance enhancements makes it a little easier to have a conversation about nutrition—and potential macular carotenoid supplementation—with your patients.
Stringham JM, Stringham NT, O'Brien KJ. Macular carotenoid supplementation improves visual performance, sleep quality, and adverse physical symptoms in those with high screen time exposure. Foods. 2017;6(7):47.
Hammond BR Jr, Wooten BR. CFF thresholds: relation to macular pigment optical density. Ophthalmic Physiol Opt.2005;25(4):315-319.
Renzi LM, Bovier ER, Hammond BR Jr. A role for the macular carotenoids in visual motor response. Nutr Neurosci.2013;16(6):262-268.
American Optometric Association. Sports and performance vision. Available at https://www.aoa.org/optometrists/tools-and-resources/sports-and-performance-vision. Last accessed 18 Jun 2020.
Dr. Stringham is a research scientist with Duke University Medical School, Department of Ophthalmology. His research includes the effects of lutein, zeaxanthin, and meso-zeaxanthin on a variety of human physiological, health, and visual performance parameters.