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  • Bryan Cui

What Does Caffeine Do To Our Eyes?

Caffeinated beverages have become standard drinks for the majority of Canadian high school students. It is commonly known that caffeine has multiple effects on the brain and the nervous system. However, what is lesser known to the public is the impact of caffeine on eyesight.

Firstly, caffeine appears to help with dry eyes, which occurs when the eyes do not produce enough tears or when tears do not have the right consistency to retain moisture in the eyes. A small experiment conducted in Japan involved giving a group of 39 people 200 to 600 mg of caffeine and another group with placebo capsules. The Japanese scientists discovered that the group who consumed the caffeinated pills produced more tears than the control group. A similar study was also conducted in Ghana and yielded nearly identical results as well.

A recent experiment conducted at the University of Waterloo investigated whether or not caffeine would affect visual acuity, also known as clarity or sharpness of vision. The study involved giving half the participants small caffeine capsules, and the other half placebo pills. Using a computer-based test at the University, the visual acuity skills of each participant were measured an hour before and after the capsules were taken. The results indicated a strong likelihood that caffeine improves visual acuity, as the group that ingested caffeine identified small moving stimuli with significantly greater accuracy and speed.

Caffeine, unfortunately, has downsides as well. Overindulgence in caffeine can lead to higher blood sugar levels, which can quickly develop into blurred vision. In addition, excessive consumption of caffeine (1000 mg a day) can cause a person to see flashes and bright lights that don’t actually exist. Caffeine is also associated with myokymia, a condition that is characterised by involuntary twitching of the eyelids. Serious caffeine consumption (3 or more cups of coffee a day) is also linked to an increased risk in developing a degenerative eye disease called glaucoma. Glaucoma is the buildup of pressure in the optic nerve, which can cause a decreased field of vision and even blindness. Consuming a lot of caffeine would also cause exfoliation, the buildup of deposits within the eye, which would lead to an increased risk of developing or worsening glaucoma.

Overall, caffeine boasts a large range of effects on the eyes. Now that caffeinated drinks have become some of the more popular beverages even among the youth, it is crucial to take time to understand both the benefits and harms of these beverages, and maybe next time you’ll think twice before sipping on another can of Red Bull, cup of coffee, or a McDonald's Iced Coffee.


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