The effect of caffeine on intraocular pressure in glaucoma patients.

The authors investigated the effect of drinking regular coffee on intraocular pressure (IOP) using a single-masked randomized crossover study comparing coffee and herbal tea in 13 glaucoma patients. Intraocular pressure and blood pressure were monitored before ingestion of coffee or tea and at 30, 60, and 90 minutes after ingestion. The mean (+/- standard error of measurement) change in IOP 30, 60, and 90 minutes after ingestion for the coffee drinkers was 0.96 +/- 0.4, 1.38 +/- 0.53, and 1.04 +/- 0.37 mmHg, respectively. The mean change in IOP for the tea drinkers 30, 60, and 90 minutes after ingestion was 0.85 +/- 0.41, 0.23 +/- 0.36, and -0.42 +/- 0.44 mmHg, respectively. There was a statistically significant difference in the change in IOP at 90 minutes when comparing coffee to tea (P = 0.003) and no significant difference for 30 and 60 minutes. Although there was a statistically significant difference in IOP at 90 minutes between coffee and tea drinkers, the change was not clinically significant.