OBJECTIVE Normal-tension glaucoma has been found to be related to transient increases in intraocular pressure (IOP). Isometric exercise induces a pressor response with a characteristic increase in blood pressure. The purpose of the present study was to investigate how transient changes in systemic blood pressure, induced by isometric exercise, affect IOP. METHODS Nine healthy volunteers participated in the study. Systemic blood pressure, heart rate (ECG) and IOP (electronic continuous-indentation tonometer) were recorded continuously before, during, and after a 2-minute period of isometric exercise (40% maximum voluntary contraction of the forearm). RESULTS During the 2-minute isometric exercise, heart rate increased from 74+/-6 beats/min (mean +/- SEM) to 93+/-6 beats/min (P<0.005) and systolic and diastolic arterial blood pressure increased from 125+/-6 to 169+/-8 mm Hg (P<0.005) and from 65+/-3 to 96+/-5 mm Hg (P<0.005), respectively. IOP increased from 15+/-1 mm Hg at rest to 19+/-2 mm Hg at the end of the isometric exercise (P<0.005). CONCLUSIONS During isometric exercise, IOP increased continuously, as long as the isometric exercise persisted, in parallel to the increase in systemic blood pressure.