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Jessica V Jasien, Daniel Turner, Jeffrey S Morris, Christopher A Girkin, J Crawford C Downs; IOP Asymmetry in Nonhuman Primates (NHPs) Measured with Continuous Telemetry. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3408.
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© ARVO (1962-2015); The Authors (2016-present)
Glaucoma is commonly worse in one eye of patients, but little is known about the underlying causes of asymmetric disease severity. IOP is a common risk factor for glaucoma, so we characterized IOP asymmetry in fellow normal eyes of NHPs instrumented with a fully implanted, continuous bilateral IOP telemetry system.
Bilateral IOP was measured and recorded 500 times per second, 24 hours a day, over long periods of time in 3 male rhesus macaques aged 3-6 years old using a proven implantable telemetry system (IOVS 52(10):7365-75). The IOP transducers were calibrated every two weeks via anterior chamber cannulation manometry and all data were continuously corrected for signal drift via software. IOP asymmetry was defined as the absolute difference between IOPs in fellow eyes, calculated over 182 to 452 days depending on the animal (Table). IOP (500 Hz) was averaged hourly in each eye and relative hourly difference between fellow eyes was calculated, then averaged across all days (Figure). 95% confidence intervals were computed and plotted, and statistical significance determined based on t-tests with Bonferroni correction for multiple testing. Waking hours are from 6:00 to 18:00 based on the NHP holding room light cycle.
Results show the IOP difference between fellow eyes is significant and varies from 0.2 to 2 mmHg (Figure). The greatest IOP asymmetry is seen during waking hours in all three NHPs. The mean IOP in the left and right eyes of each NHP is shown in the table.
IOP asymmetry is large and persistent in some NHPs, and varies with the time of day. If this result translates to humans, IOP asymmetry may underlie the asymmetric glaucoma severity commonly seen in patients, and hence IOP asymmetry should be considered in clinical management of glaucoma.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Table. Mean 24-Hour IOP OU, Mean 24-Hour IOP Asymmetry (mmHg) and the total days of data analyzed by NHP.
Figure. 24-Hr IOP Asymmetry by NHP. Green lines represent the 95% Confidence Interval. Waking hours are highlighted.
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