Caffeine produces a few physiological effects, including slightly raised blood pressure and increased heart rate. It is a vasoconstrictor (i.e. it affects blood vessels) and it also affects muscle contractility; these things, infact do make it possible for caffeine to have a slight effect on eye pressure. In a study of 63 adults, healthy young adults were given varying doses of caffeine, and in the high-dose group (taking 340mg caffeine) there was a statistically significant but relatively small rise of over 2mmHg after 90 minutes. Infact there was little change between groups when IOPs were measured only 30 minutes after drinking caffeine. Caffeine is in a number of products, including coffee, tea, coca cola, energy drinks and chocolate.

Here is a list of the approximate amounts of caffeine in various drinks and foods:

Coffee 140mg

Expresso (single shot) 106mg

Grande cup of coffee (16 oz) 300mg

Starbucks Tall coffee 260mg

Coke Zero 45mg

Diet coke 45mg

Fanta 0mg

Mountain Dew 54mg

Pepsi Max 69mg

Lipton iced tea 48mg

Green tea 25mg (typically there is less caffeine in green tea varieties)

Patients who have glaucoma or ocular hypertension, who are heavy coffee drinkers, or who have a high intake of caffeine, should be advised to limit their consumption.


Green tea has a relatively low caffeine content