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R. P. Dresher, E. Y. Chow, B. N. Fogle, T. Maleki, G. Simon, J. M. Clevenger, B. Ziaie, P. P. Irazoqui; Improving Glaucoma Treatment: An Implantable IOP Monitor Providing Uninterrupted Measurements. Invest. Ophthalmol. Vis. Sci. 2008;49(13):686.
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To develop an IOP monitor that overcomes the limitations of current technologies. Specifically, an implantable monitor that provides uninterrupted measurements twenty-four hours a day, requires minimal patient interaction, and eliminates the need for a permanent communication/powering link between the implanted device and external data-logging unit.
An implantable IOP monitor consisting of a powering module, application specific integrated circuit (IC), and pressure sensor were designed and fabricated using IC and Biological Micro Electro Mechanical Systems (BioMEMS) technologies. Studies that varied air pressure from 0 - 100 mmHg were done to verify and characterize the functionality of the sensor. In silico studies were utilized to quantify the measurement performance of the IOP monitor. Preliminary bench-top electrical testing of the fabricated IC is currently being conducted.
The fabricated and assembled device is coated with parylene for biocompatibility. The pressure sensor provides an approximately linear output with linear changes of pressure in the tested range. In silico studies verify that the IOP monitor can provide uninterrupted measurements twenty-four hours a day without the need for a permanent communication/powering link. In a twenty-four hour period, the patient must interact with the device only once for a few seconds. The monitor has a simulated resolution of 2 mmHg and can sample IOP once every 5 minutes. Preliminary bench-top testing of the individual circuits of the IC validates their functionality, but suggests that further improvements can be made.
The first prototype IOP monitor shows great potential for improving glaucoma treatment by providing the ability to obtain numerous measurements during all daily activities, even during sleep. Minimal patient interaction helps to preserve the patient’s quality of life. Future research includes further miniaturization of the implanted device, improving the resolution to 0.5 mmHg, biocompatibility and hermeticity testing of improved biomaterials for encapsulation, and in vivo animal studies.
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