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Daniel C Turner, Lisa A Hethcox, Christopher A Girkin, J Crawford C Downs; Changes in IOP with Body Position Using Continuous Bilateral IOP Telemetry. Invest. Ophthalmol. Vis. Sci. 2014;55(13):116.
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© ARVO (1962-2015); The Authors (2016-present)
To study the effect of body position on IOP in nonhuman primates (NHPs) using continuous bilateral IOP telemetry.
We have developed and validated an implantable telemetry system that wirelessly records 500 measurements of IOP per second for up to 2-1/2 years (IOVS 52(10):7365-75). Using an enhanced version of this system, continuous bilateral IOP, bilateral electro-oculogram (EOG), and aortic blood pressure were recorded at seven different body positions while anesthetized (ketamine/dexdomitor) in two different sessions 2 weeks apart in 3 young adult male rhesus macaques (NHP) aged 3-6 years old. IOPs were recorded continuously while the NHPs were in the upright seated position, standing up, supine, lying on the right shoulder in the recumbent position, lying on left shoulder in the recumbent position, and lying with head facing forward in the prone position. Measurements were taken for 1.5 minutes in each position before returning to a baseline supine position until IOP stabilized. After changing body position, IOP was averaged for 1 minute after it reached steady-state, and compared to the baseline IOP in the supine position.
Baseline IOP was determined by averaging six recordings of 1 minute in the supine position. As seen in the Table, IOPs changed most in the inverted head-down position (increase of 8.4 mmHg over baseline). In the lateral recumbent positions, the eye at higher elevation (i.e. OS while lying in the right lateral recumbent position) had an average decrease of 2.3 mmHg, while the lower elevation eye averaged a decrease of only 0.1 mmHg. The prone position revealed an average decrease of 2.9 mmHg compared to baseline, while in the seated upright position and standing decreased 3.3 and 3.2 mmHg respectively. IOP reached steady-state values within 15 seconds after positional change.
Body orientation has a significant effect on IOP in the NHP and IOP changes occurred very rapidly after positional change.
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