Several energy drinks containing a high content of caffeine are widely consumed among young adults. We examined the effects of caffeinated energy drinks on intraocular pressure (IOP) and blood pressure (BP) in healthy young subjects.

In this prospective randomized, case-controlled cross over study conducted, from August to September of 2014, 40 healthy young volunteers (80 eyes) in their 20's and 30's drank 2 types of beverage each consumed after a 3-month washout period. The study participants were randomly given the caffeinated energy drink (group I, n = 20) or caffeine-free drink (group II, n = 20), IOP and BP were measured at 0, 30, 60, 90, and 120 minutes and 12 and 24 hours after beverage consumption.

In group I, the mean ± standard deviation (SD) of IOP at baseline was 13.2 ± 1.56 mm Hg and the IOP increased until 24 hours after drink consumption. IOPs at 30, 60, 90, and 120 minutes and 12 and 24 hours after drinking caffeinated energy drink were 14.45 ± 2.12, 14.93 ± 2.02, 14.85 ± 1.55, 14.2 ± 1.34, 14.25 ± 1.74, and 13.35 ± 1.61, respectively and statistically significant at 30, 60, 90, 120 minutes and 12 hours ( p < 0.05). A corresponding increase in BP after drinking the caffeinated energy drink was observed but without statistical significance. Drinking the caffeine-free beverage did not affect IOP or BP significantly.

IOP increases after consuming the caffeinated energy drink were statistically significant at 30, 60, 90, and 120 minutes and 12 hours. Therefore, caffeinated energy drinks may not be recommended for glaucoma patients or glaucoma suspects.