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J Crawford C Downs, Sonia Kuhn Asif, Lindsay Anne Rhodes, Brian C Samuels, Jessica V Jasien; Comparison of Extraocular (EO) and Intraocular (IO) Pressure Transducers for Measurement of Transient IOP Fluctuations Using Continuous Wireless Telemetry. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4771.
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We have developed and validated three wireless implantable telemetry systems: two that measure IOP using an orbital wall-mounted extraocular (EO) pressure transducer connected to the anterior chamber (AC) via a fluid-filled tube (Konigsberg Instruments EO and TSE-Systems Stellar EO), and a third where a pressure transducer is placed directly into the AC (TSE-Systems Stellar Intraocular (IO)). The purpose of this study was to compare transient IOP fluctuations measured with EO and IO pressure transducers.
The frequency, magnitude, and mechanical energy of transient IOP fluctuations <3 s in duration were quantified using an automated approach in 9 eyes of 6 male rhesus macaques (NHPs) for 16-453 days using the Konigsberg EO system, as reported in our previous study (IOVS 2019;60(7):2572-2582). For this study, transient IOP fluctuations were similarly quantified in 16 eyes of 12 male NHPs using the Stellar IO system (22-376 days); in 12 eyes of 8 of these same NHPs, data were also acquired using the Stellar EO system (12-89 days) after a second implantation. IOP transducers were calibrated every 2 weeks via AC manometry, and data were adjusted for transducer drift. The Konigsberg EO system measured IOP continuously at 500Hz, whereas the Stellar EO and IO systems measured IOP at 200Hz at a 10% duty cycle (15s of every 150s period); all Stellar data were interpolated to estimate continuous sampling for direct comparison to our published Konigsberg EO data.
All three telemetry systems (EO and IO) captured 8,000-12,000 transient IOP fluctuations per hour >0.6 mmHg and 3,000-5,000 fluctuations/hour >5 mmHg above momentary baseline during waking hours, as well as 5,000-6,500 fluctuations/hour >0.6 mmHg during sleeping hours (Figure). These transient IOP fluctuations represented 8-16% of the total IOP energy the eye must withstand during waking hours, and 4-8% during sleeping hours for all systems (Figure).
For the purposes of IOP telemetry, transient IOP fluctuations can be captured using either a pressure transducer placed directly in the eye, or with a transducer mounted remotely and connected to the eye via a fluid-filled tube. However, care should be taken to minimize hydrostatic pressure effects from head position by mounting the EO sensor adjacent to the eye.
This is a 2020 ARVO Annual Meeting abstract.
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