PURPOSE: To investigate 24-hour intraocular pressure (IOP) changes caused by hemodialysis (HD).METHODS: A prospective, observational, comparative 24-hour trial was performed on consecutive subjects with normal IOP undergoing maintenance HD 3 days a week between 13:00 and 17:00 hours in an academic setting. Following a comprehensive ocular assessment, those with conditions that may influence IOP were excluded and one eye was randomly selected. Twenty-four-hour IOP monitoring was performed on HD day 1 and then on a day without HD. The IOP was measured at 10:00, 13:00, 15:00, 17:00, 22:00, 02:00, and 06:00 employing Goldmann and Perkins tonometry on habitual position. During the course of 1 year, 18 patients completed the study.RESULTS: Monitoring of IOP on HD day showed a significantly higher mean 24-hour IOP (15.4 ± 2.7 vs 14.1 ± 2.2 mm Hg; p = 0.025), higher mean peak 24-hour IOP (18.5 ± 3.5 vs 15.8 ± 2.5 mm Hg; p = 0.003), and wider 24-hour IOP fluctuation (6.2 ± 2.3 vs 4.0 ± 1.9 mm Hg; p = 0.001). When individual time points were compared, IOP was significantly higher at 17:00 on HD day, reflecting a gradual IOP elevation during HD (p = 0.021). Further, during the HD procedure (13:00-17:00), the mean IOP was significantly higher on a HD day (16.4 ± 3.0 vs 14.7 ± 2.4 mm Hg; p = 0.004).CONCLUSIONS: This prospective, before/after trial suggests that HD significantly impacts 24-hour IOP characteristics in normotensive eyes. The long-term significance of these findings requires further elucidation in normotensive patients and, predominantly, in patients with glaucoma undergoing HD.