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J Crawford C Downs, Daniel Turner, Christopher A Girkin; Evidence for the "White Coat Effect” on IOP Measured Using Continuous IOP Telemetry in Nonhuman Primates. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6466.
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© ARVO (1962-2015); The Authors (2016-present)
IOP is the most common independent risk factor for development and progression of glaucoma, but very little is known about the dynamics of IOP because it is typically measured clinically using a snapshot device every 3-12 months. We hypothesize that IOP is affected by patient stress (the white coat effect), which could alter clinically measured IOPs and possibly interfere with glaucoma management. We tested the effect of environmental stress on nonhuman primates (NHP) instrumented with a proven IOP and arterial blood pressure radiotelemetry system.
Continuous bilateral IOP and mean aortic blood pressure (MAP) was recorded 500 times per second in 3 NHPs using a proven wireless telemetry system. These variables were averaged for 8-30 seconds immediately before, during, and immediately after a common anesthetic procedure (cage squeeze followed by intramuscular injection; Figure). Relative changes in IOP, MAP, and heart rate (HR) were calculated and compared to steady-state values (Figure). Experiments were repeated 4 times at least 2 weeks apart in each animal.
IOP, MAP, and HR increased rapidly and significantly by 27%, 38%, 34%, respectively, in anticipation of anesthetic induction (Figure; p<0.01). IOP rose ~10% within 10 seconds of hearing the technician enter the outer anteroom door, and reached it’s maximum within ~1 minute of first anticipating human contact. IOP fell to below baseline levels within 1 minute after anesthetic induction.
Results demonstrate that IOP increases rapidly and significantly in response to stressful situations in the NHP. Also, IOP fluctuates widely in the NHP, which indicates that snapshot IOP measurements may be inadequate to capture the true dynamic character of IOP in humans. If the “white coat effect” on IOP and IOP flucutations exist in humans, the reliability of snapshot IOP measurements in clinical settings could be compromised, especially when the patient is stressed.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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