ABSTRACT

Despite the prevalent and regular use of caffeine, there is a notable deficiency in our comprehensive understanding of its specific effects on crucial visual parameters. While existing research recognizes the general stimulant properties of caffeine and its impact on cognitive and physiological functions, there exists a distinct gap in knowledge concerning its specific influence on the detailed mechanisms governing visual accommodation, pupillary changes, and convergence. This study aimed to investigate the effect of caffeine on amplitude of accommodation (A of A), pupil size and near point of convergence (NPC). Using an experimental study design, data were collected and analyzed using Statistical Packages for Social Sciences (SPSS), version 25, alongside other statistical tests like the Karl Pearson Correlation coefficient, Bonferroni post hoc test and Repeated ANOVA test. There were 30 participants predominantly aged between 22-24 years with a mean age of 23.60 ± 2.22 years, and an equal distribution of gender. The results of this study showed that the ingestion of 4mg/kg (dissolved in 200ml) of caffeine had no effect (p > 0.05) on pupil size (p = 0.900) across different time intervals of measurements (20, 40, 60 minutes). Similarly, there was also no effect of caffeine ingestion on A of A both on the right eye (p = 0.068) and left eye (p = 0.070). However, the consumption of caffeine had an effect both on the break and recovery points (p = < 0.001). Break point increased from 7.7667 (± 2.05415 cm) at baseline to 10.5333 (± 2.30417 cm) at 60 minutes. Recovery point increased from 10.0833 (± 2.25176 cm) at baseline to 12.8833 (± 2.57870 cm) at 60 minutes. There was no correlation between the A of A and pupil size, the break point and A of A, and the break point and pupil size (r < 0.3; p > 0.05). In conclusion, this study showed that while caffeine does not appear to affect the A of A or pupil size, it does have an effect on the NPC. Furthermore, no correlations were found between these visual parameters, suggesting independent responses to caffeine ingestion. These findings contribute to our understanding of the physiological effects of caffeine on visual function and have implications for individuals who consume caffeinated beverages regularly.

Keywords: caffeine, amplitude of accommodation, pupil size, near point of convergence.