Purposes: The primary aim of the study was to assess the response of intraocular pressure (IOP) to the acute ingestion of hydrogen-rich water (HRW) compared to hydrogen-free water (placebo) in healthy subjects. The effect of HRW intake on central corneal thickness (CCT) was also monitored. Subjects and methods: Twenty-four healthy volunteers (5 men, 19 women) aged between 20 and 33 were included in the study, in which one eye of each subject was measured. The study was prospective, randomized and double-blind, with crossover design. Each subject underwent two parts of the experiment, each part on a different day and in random order. In each part of experiment, a total volume of 1260 ml of HRW or placebo was administered over 15 minutes in three doses. IOP and CCT were measured before and during the course of 75 minutes from the start of the HRW or placebo intake. Results: Administration of both HRW and the placebo caused a significant increase in IOP. The maximum IOP increase was 2.7 mmHg ±2.0 mmHg in minute 25 after the commencement of the experiment (HRW intake), and 1.4 mmHg ±2.0 mmHg in minute 35 (placebo intake). The values of IOP did not differ significantly between both parts, but there were significantly more clinically significant individual IOP increases after HRW intake (58%) compared to the placebo (25%). CCT did not change significantly during the experiment. Conclusion: The rapid intake of 1260 ml of both HRW and hydrogen-free water causes a statistically significant increase in IOP compared to the baseline in healthy individuals. In the case of HRW, the increase was also clinically significant in most of the subjects. Thus, the results indicate that acute intake of HRW may pose a higher risk than placebo intake in terms of IOP. However, in the case of risk groups such as subjects with glaucoma, ocular hypertension or suspected glaucoma, it is necessary to verify this conclusion by further studies.