Comparison of extraocular and intraocular pressure transducers for measurement of transient intraocular pressure fluctuations using continuous wireless telemetry

Jessica V Jasien,Lindsay A Rhodes,Brian C Samuels,Christopher A Girkin,Ye Emma Zohner,J Crawford Downs,Sonia Kuhn Asif,Jeffrey S Morris

doi:10.1038/s41598-020-77880-8

Jessica V Jasien, Lindsay A Rhodes + Show 6 more

Open Access

https://doi.org/10.1038/s41598-020-77880-8

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Abstract

The optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown. This study assessed the capability of extraocular (EO) and intraocular (IO) pressure transducers, using different IOP sampling rates and duty cycles, to characterize IOP dynamics. Transient IOP fluctuations were measured and quantified in 7 eyes of 4 male rhesus macaques (NHPs) using the Konigsberg EO system (continuous at 500 Hz), 12 eyes of 8 NHPs with the Stellar EO system and 16 eyes of 12 NHPs with the Stellar IO system (both measure at 200 Hz for 15 s of every 150 s period). IOP transducers were calibrated bi-weekly via anterior chamber manometry. Linear mixed effects models assessed the differences in the hourly transient IOP impulse, and transient IOP fluctuation frequency and magnitude between systems and transducer placements (EO versus IO). All systems measured 8000–12,000 and 5000–6500 transient IOP fluctuations per hour > 0.6 mmHg, representing 8–16% and 4–8% of the total IOP energy the eye must withstand during waking and sleeping hours, respectively. Differences between sampling frequency/duty cycle and transducer placement were statistically significant (p < 0.05) but the effect sizes were small and clinically insignificant. IOP dynamics can be accurately captured by sampling IOP at 200 Hz on a 10% duty cycle using either IO or EO transducers.

Highlights

The optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown
Existing telemetry systems have a wide range of sampling frequencies and duty cycles that may or may not capture the transient IOP fluctuations occurring in the e ye[15,16]
We have developed and validated three wireless implantable IOP telemetry systems for research use, two that measure IOP using a tube inserted into the anterior chamber connected to an extraocular (EO) pressure transducer mounted in the orbital wall (Konigsberg Instruments EO or TSE-Systems Stellar EO), and a third where an intraocular (IO) pressure transducer was implanted in the anterior chamber of the eye (TSE-Systems Stellar IO)

Summary

Introduction

The optimal approach for continuous measurement of intraocular pressure (IOP), including pressure transducer location and measurement frequency, is currently unknown. This study assessed the capability of extraocular (EO) and intraocular (IO) pressure transducers, using different IOP sampling rates and duty cycles, to characterize IOP dynamics. Existing telemetry systems have a wide range of sampling frequencies and duty cycles that may or may not capture the transient IOP fluctuations occurring in the e ye[15,16]. Powering an intraorbital device that measures transient IOP fluctuations is a difficult engineering problem, as high sampling frequencies and continuous operation require too much power and generate too much heat to be practical. Placing the IOP transducer in an extraocular reservoir connected to the eye via a tube has measurement accuracy advantages, but a tube-based approach has the potential to damp and/or alter transient IOP fluctuation assessment through reservoir system elasticity and tube bending artefact. Data transmission requires significant energy and generates heat, so IOP telemetry systems must grapple with the trade-offs associated with providing sufficient IOP sampling to Scientific Reports | (2020) 10:20893 |

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