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Jessica V Jasien, Massimo A Fazio, Brian C Samuels, James M Johnston, J Crawford C Downs; IOP, Intracranial Pressure, Translaminar Pressure and Translaminar Pressure Gradient Quantified with Continuous Wireless Telemetry in Nonhuman Primates. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3530.
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© ARVO (1962-2015); The Authors (2016-present)
Recent retrospective clinical studies and animal experiments suggest cerebrospinal fluid pressure (CSFP) is important in glaucoma pathogenesis. Intraocular pressure (IOP) and CSFP are the driving components of translaminar pressure (TLP = IOP - CSFP), which acts across the lamina cribrosa (LC) thickness to create the translaminar pressure gradient (TLPG = TLP / LC Thickness); both directly affect the optic nerve head. The lack of continuous and accurate IOP and CSFP measurement has impeded research into the roles of IOP, TLP, and TLPG in glaucoma.
We developed an implantable wireless pressure telemetry system based on a small piezoelectric sensor with low drift. Unilateral IOP is measured from the anterior chamber and intracranial pressure (ICP) is measured from the brain parenchyma (as a surrogate measure of CSFP) in nonhuman primates (NHPs). Waking hours are defined as 6:00-18:00 and sleeping hours as 18:00-6:00, based on 12-hour light/dark cycle in the NHP holding room. IOP and ICP data were collected in three male rhesus macaques on a 10% duty cycle, consisting of 200 measurements per second captured for 15s of every 150s period over a range of 69 to 281 days. Three-dimensional LC thickness was defined as the overall mean thickness of the hyper-reflective band within 48 radial SD-OCT B-scans taken through the center of each optic nerve head at 7.5-degree increments.
Table 1 shows the rank order of IOP, ICP, TLP, and TLPG for the waking, sleeping and 24-hour periods averaged across all days. While NHP 150069 had the lowest IOP and ICP in all periods, it had the highest TLPG in all periods due to its relatively thin LC. Similar shifts in the rank order of possible glaucoma risk factors were observed for the other two NHPs as well.
IOP is the only modifiable and readily measurable pressure-based risk factor for glaucoma. However, other potential risk factors such as ICP, TLP and TLPG exist and their rank order patterns may differ compared to IOP across subjects, demonstrating that a comprehensive view of relevant risk factors is warranted.
This is a 2020 ARVO Annual Meeting abstract.
Table 1. Average IOP, ICP, TLP and TLPG (mean ± standard deviation) for the waking (6:00-18:00) and sleeping (18:00-6:00) periods across all days by NHP, presented in color-coded rank order.
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