Upon investigating the differences in intraocular pressure (IOP) and ocular perfusion pressure (OPP) between low- and high-caffeine consumers, a team of Spanish researchers found that IOP responsiveness to caffeine ingestion is subject to tolerance effects and could be due to alterations in the adenosine receptor system caused by chronic caffeine consumption; the findings could have important implications for glaucoma management, they suggest.

This placebo-controlled, double-blind, balanced crossover study evaluated 40 healthy patients and divided them between low and high caffeine consumption groups based on their daily intake. IOP and OPP were measured 30, 60 and 90 minutes after ingesting caffeine or placebo.

The researchers found that caffeine induced an acute IOP rise; habitual caffeine users demonstrated a mediating effect on the IOP changes induced by caffeine intake, with high-caffeine consumers showing a less accentuated IOP rise in comparison with low-caffeine consumers. They note that the greatest IOP change induced by caffeine intake was reached 90 minutes after ingestion and was more accentuated for the low-caffeine consumers (+3.4mm Hg) than for the high-caffeine consumers (+1.2mm Hg). The team notes that their findings did not reveal any effect of caffeine consumption on OPP.

Vera J, Redondo B, Molina R, et al. Psychopharmacology. Effects of caffeine on intraocular pressure are subject to tolerance: a comparative study between low- and high-caffeine consumers. Psychopharmacology November 11, 2018. [Epub ahead of print].