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Pooja Godara, Daniel Turner, Kevin J Byrne, Christopher A Girkin, J Crawford C Downs; Intra-subject Variability of Ocular Perfusion Pressure (OPP) via 24-hour Telemetry in Nonhuman Primates (NHP). Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6148.
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© ARVO (1962-2015); The Authors (2016-present)
To test the hypothesis that bilateral OPP differs between NHPs as characterized via continuous radio telemetry of bilateral IOP and aortic blood pressure (BP).
We have developed and validated an implantable IOP telemetry system that wirelessly records 500 measurements 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 (BP) were recorded 24 hours/day for a period of 60-70days in four young adult male rhesus macaques aged 3-6 years old. Bilateral IOP measurements were taken in 3 NHPs and unilateral measurements acquired in 1 NHP. The IOP transducers were calibrated directly via anterior chamber manometry, and OPP was calculated 500 times per second as: central retinal artery (CRA) BP - IOP. The CRA systolic and diastolic BPs were calibrated directly to the aortic systolic and diastolic BPs recorded by the telemetry system via ophthalmodynamometry, by visualizing the IOPs at which the CRA begins to flutter (diastolic) and fully collapse (systolic). OPP data was corrected for signal drift, and averaged hourly.
As seen in the Figure, OPP was consistent between contralateral eyes but varied widely between animals, ranging from daily averages of ~17 mmHg to ~62 mmHg. OPP was lowest during the night, increased upon waking and was highest in late afternoon in all four NHPs. Nycthemeral fluctuations in mean OPP also varied widely between animals.
Average OPP varies widely between NHPs, is consistent between contralateral eyes within NHPs, is highest in afternoon and evening, and is lowest at night. OPP differences between animals are significant, which may put the NHPs with lower OPPs at risk for ischemic damage at lower IOP levels.
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