CLARO (Clinical and Laboratory Applications of Research in Optometry) Research Group, Department of Optics, Faculty of Sciences, University of Granada, Granada, Spain.
Department of Computer Science, Durham University, Durham, UK.
Clin Exp Optom. 2022 Jul;105(5):534-538. doi: 10.1080/08164622.2021.1935218. Epub 2021 Jun 16.
Caffeine intake has been demonstrated to influence several physiological measures, including some related to eye physiology. The ability to focus at different distances is of paramount importance in real-world situations, and thus, the possible impact of caffeine intake on accommodative facility may have important clinical implications.
This placebo-controlled, double-blind, balanced crossover study aimed to assess the acute effects of caffeine ingestion on the frequency and precision of the binocular accommodative facility.
Twenty university students (21.9 ± 3.4 years) ingested a capsule of caffeine (4 mg/kg) or placebo (300 mg of corn-starch) on two different days and counterbalanced order. The binocular accommodative facility was objectively assessed, using the WAM-5500 binocular open-field autorefractometer, after 60 min of capsule ingestion (caffeine/placebo). Perceived levels of activation was also assessed in each experimental condition.
The ingestion of a single administration of caffeine (~ 4 mg/kg) causes an increase in the number of cycles performed per minute (p = 0.023, Cohen's d = 0.55), whereas no effects were observed for the mean magnitude of accommodative change between the far and near targets (p = 0.794), and the percentage of incorrect cycles of accommodation and dis-accommodation (p = 0.271 and 0.396, respectively). Participants reported a perceived level of activation of 6.8 ± 1.5 and 7.6 ± 1.8 in the placebo and caffeine conditions, respectively (p = 0.059).
Caffeine intake improves quantitative, but not qualitative, measures of accommodative facility. These results corroborate the impact of caffeine on visual function and suggest that this ergogenic effect of caffeine may be used to enhance visual performance in applied situations.
咖啡因的摄入已被证明会影响几种生理指标，包括一些与眼睛生理有关的指标。在现实情况下，能够在不同距离聚焦是至关重要的，因此，咖啡因摄入对调节灵活度的可能影响可能具有重要的临床意义。
本项安慰剂对照、双盲、平衡交叉研究旨在评估咖啡因摄入对双眼调节灵活度的频率和精度的急性影响。
20 名大学生（21.9±3.4 岁）在两天内分别服用咖啡因（4mg/kg）或安慰剂（300mg 玉米淀粉）胶囊，并以平衡方式交替进行。在胶囊摄入后 60 分钟（咖啡因/安慰剂），使用 WAM-5500 双眼开放式自动折射计客观评估双眼调节灵活度。在每个实验条件下，还评估了感知的激活水平。
单次摄入咖啡因（约 4mg/kg）会导致每分钟完成的周期数增加（p=0.023，Cohen's d=0.55），而远、近目标之间的调节变化平均幅度（p=0.794）以及调节和去调节周期的错误百分比（p=0.271 和 0.396，分别）没有观察到效果。参与者在安慰剂和咖啡因条件下分别报告了 6.8±1.5 和 7.6±1.8 的感知激活水平（p=0.059）。
咖啡因摄入可改善调节灵活度的定量指标，但不能改善定性指标。这些结果证实了咖啡因对视觉功能的影响，并表明咖啡因的这种促进作用可能被用于提高应用情境中的视觉表现。
