Development of a Smart Pump for Monitoring and Controlling Intraocular Pressure
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Animal models of ocular hypertension are important for glaucoma research but come with experimental costs. Available methods of intraocular pressure (IOP) elevation are not always successful, the amplitude and time course of IOP changes are unpredictable and irreversible, and IOP measurement by tonometry is laborious. Here we present a novel system for monitoring and controlling IOP without these limitations. It consists of a cannula implanted in the anterior chamber of the eye, a pressure sensor that continually measures IOP, and a bidirectional pump driven by control circuitry that can infuse or withdraw fluid to hold IOP at user-desired levels. A portable version was developed for tethered use on rats. We show that rat eyes can be cannulated for months without causing significant anatomical or physiological damage although the animal and its eyes freely move. We show that the system measures IOP with <0.7 mmHg resolution and <0.3 mmHg/month drift and can maintain IOP within a user-specified window of desired levels for any duration necessary. We conclude that the system is ready for cage- or bench-side applications. The results lay the foundation for an implantable version that would give glaucoma researchers unprecedented knowledge and control of IOP in rats and potentially larger animals.
KeywordsGlaucoma Rat Telemetry Eye Implant Closed loop control
The work was supported by NIH grant R21 EY023376 and a Thomas R. Lee Award from the BrightFocus Foundation. The authors thank Drs. Radouil Tzekov and Xiaolan Tang for assistance with histological processing, Dr. Wilfredo Moreno for consultations with controller design, and Dr. Curtis Margo for evaluating the pathology of implanted eyes. The authors declare the following intellectual interests: U.S. Patents 9022,968 B2 and 9314,375 B1.
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