Caffeine linked to IOP elevation

Too much caffeine may contribute to elevations of intraocular pressure (IOP), according to findings from a double-blinded, randomized controlled trial.

Caffeine is known to produce a number of physiologic changes, including an increase in blood pressure. Animal studies show it can increase aqueous production, plus it can reduce aqueous drainage, according to Dr. Atchareeya Wiwatwongwana from the department of ophthalmology at Chian Mai University, Thailand who presented the study at the 5th World Glaucoma Congress.

A total of 63 healthy young adults (about half were female) were randomly assigned to one of three coffee-drinking groups, with 21 subjects in each. People with a baseline IOP of 21mmgHg or higher were excluded. Subjects were asked to avoid beverages which contained caffeine for three days before the study.

IOP was measured prior to coffee consumption, and again 30, 60 and 90 minutes after drinking coffee. Each subject was given 250 ml of coffee, with the caffeine levels being 2 mg of caffeine in the decaffeinated group; 170 mg in the second group, and 350 mg in the third.

Baseline IOP was an average of 13.25 mmgHg across the groups. After coffee consumption, there was a mild non-statistically significant rise in IOP at 90 minutes in the decaffeinated and 170 mg caffeine groups. However, the high dose group had an significant increase in IOP to just over 15 mmHg.

This effect "could have clinical implications for screening and monitoring of glaucoma patients," the researchers said.