A Wireless Pressure Sensor for ContinuousMonitoring of Intraocular Pressure in Conscious Animals.

Abstract

An important aspect of eye health in humans and animal models of human diseases is intraocular pressure (IOP). IOP is typically measured by hand with a tonometer, so data are sparse and sporadic and round-the-clock variations are not well characterized. Here we present a novel system for continuous wireless IOP and temperature measurement in small animals. The system consists of a cannula implanted in the anterior chamber of the eye connected to pressure sensing electronics that can be worn by rats or implanted in larger mammals. The system can record IOP with 0.3mmHg accuracy and negligible drift at a rate of 0.25Hz for 1-2months on a regulated battery or indefinitely at rates up to 250Hz via RF energy harvesting. Chronic recordings from conscious rats showed that IOP follows a diurnal rhythm, averaging 16.5mmHg during the day and 21.7mmHg at night, and that the IOP rhythm lags a diurnal rhythm in body temperature by 2.1h. IOP and body temperature fluctuations were positively correlated from moment-to-moment as well. This technology allows researchers to monitor for the first time the precise IOP history of rat eyes, a popular model for glaucoma studies.