Recent studies show that drinking coffee can increase intraocular pressure (IOP), but the novelty is that not due to caffeine as it also occurs in those who consume coffee decaffeinated. It seems that the cause of increased IOP is endogenous substances contained coffee beans that appear with the high temperatures reached in the roast process.
It has long been association between coffee consumption with a higher risk of increased intraocular pressure (IOP) and although there are different opinions, it seems that the evidence from recent studies in large groups of people, show a clear relationship causing effect.
In one of the most comprehensive and broad study, with 78,977 women and 41,202 men, found an increased risk of elevated intraocular pressure in individuals who consumed more than three cups of coffee a day, being even higher in women and when a family history of glaucoma was present. This study was interesting because found that the risk of ocular hypertension associated with coffee, was not given with the consumption of other caffeinated beverages, such as soda, chocolate or tea. (The Relationship Between caffeine and coffee consumption and exfoliation glaucoma or glaucoma suspect: a prospective study in two cohorts. Pasquale LR, Wiggs JL, Willett WC, Kang JH. Invest Ophthalmol Vis Sci 2012 Sep 21; 53 (10): 6427 - 33).
To determine if the cause of the elevation of the IOP is due to caffeine or another element of coffee, there have been several studies. One of the most significant is the Blue Mountains Eye Study, which shows that while there was an increase in IOP in coffee drinkers, this increase was similar in those who drank caffeinated coffee and decaffeinated coffee consuming. (Effects of caffeine on intraocular pressure: the Blue Mountains Eye Study. Chandrasekaran S, Rochtchina E, Mitchell P. J Glaucoma. 2005 Dec, 14 (6) :504-7).
To be more precise on the role of caffeine, another study where caffeine was injected directly into the eye, showed that there was not an increase in IOP, concluding that caffeine is not the cause of the pressure changes in the coffee intake. The authors indicate that the increased IOP may be due to other endogenous coffee products which appear with the high temperatures reached in the pyrolytic process of roasting, combined with other osmotic effects on changes taking place in the metabolism of aqueous humor. (Clin Effect of caffeine on the intraocular pressure in patients with primary open angle glaucoma. Chandra P, Gaur A, Varma S. Ophthalmol. 2011; 5:1623-9. Epub 2011 Nov 16).