The short-term effects of energy drinks on near visual performance

Abstract

Background: Energy drinks have gained popularity amongst young adults in recent years. Widespread effects of its main ingredient caffeine have been observed on the nervous system; however, little is known about the effects of these drinks on the visual system.

Aim: This research study investigated the effects of a chosen energy drink on near vision and near contrast sensitivity.

Setting: The data were collected at a university optometry clinic in south eastern South Africa.

Methods: A single-blinded, crossover study was conducted on 56 healthy subjects aged 18–30 years. Subjects were randomised, such that they consumed either the energy drink reboost or water (control) on separate days. Near visual acuity was measured using a near Logarithm of the Minimum Angle of Resolution (LogMAR) chart and contrast sensitivity using the MARS contrast sensitivity test. Near visual acuity and contrast sensitivity measurements were taken at baseline and again at 30 min, 60 min and 90 min intervals, following consumption. Data were analysed using repeated measures analysis of variance (ANOVA) and univariate analysis.

Results: Both near visual acuity and contrast sensitivity, post-energy drink consumption, showed a marginal increase over the testing period. Near visual acuity increased from –0.13 LogMAR at baseline to –0.17 LogMAR at 90 min. Contrast sensitivity increased from 1.77 log units at 30 min to 1.78 log units at 90 min similar to that observed with the control. In both cases; however, the changes were neither statistically (p > 0.05) nor clinically significant.

Conclusion: The energy drink reboost had no short-term effect on near vision performance as measured with near visual acuity and contrast sensitivity.