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S. O. Semb, E. F. Bakke; Changes in Intraocular Pressure and Pulsatile Ocular Blood Flow Measured Continuously During Isometric Exercise. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4130.
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Isometric exercise induces an exercise pressor response with a characteristic increase in blood pressure and thereby ocular perfusion pressure (OPP). In this study we wanted to examine the continuously changes in intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) related to changes in finger arterial blood pressure (BP) before, during and immediately after isometric exercise.
Nine healthy young subjects participated. BP, heart rate (HR) and IOP were continuously recorded at 300 Hz before, during and after 2 min of 40% maximum voluntary contraction of the forearm. Finger arterial pressure was acquired by a photoplethysmographic pressure measuring device (Finometer). IOP was continuously recorded from the subjects left eyes with an ocular dynamic tonometry (an electronic Schiøtz tonometer.
Mean IOP before exercise was 14.1 mmHg (± SEM, ± 1.4). During the 2 min of exercise heart rate increased from 75 ± 6 to 93 ± 6 beats/min (P<0.003) and systolic and diastolic arterial pressure increased from 122 ± 6 to 165 ± 7 (P<0.001) and 63 ± 3 to 95 ± 5 mmHg (P<0.005), respectively. Relative changes in IOP measured, increased by 4.8 mmHg (34%) during the same time period. Hence a 46% increase in calculated ocular perfusion pressure. During recovery IOP fell with a time constant of 56.4 ± 9.5 s 16% in 14 ± 6.2 s (P<0.001). Systolic blood pressure fell with a similar time constant (63.0 ± 7.4 s). The POBF fell by 23% when comparing the values during the initial resting period with the wave-forms at the end of the exercise period.
This study is the first to measure continuously IOP, the pulsatile wave-form of IOP, heart rate and blood pressure during isometric exercise and it shows that IOP changes in parallel with blood pressure. There is either a decrease in ocular blood flow during isometric exercise or a shift from pulsatile to non-pulsatile ocular blood flow.
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