A Miniature-Implantable RF-Wireless Active Glaucoma Intraocular Pressure Monitor

Abstract

Glaucoma is a detrimental disease that causes blindness in millions of people worldwide. There are numerous treatments to slow the condition but none are totally effective and all have significant side effects. Currently, a continuous monitoring device is not available, but its development may open up new avenues for treatment. This work focuses on the design and fabrication of an active glaucoma intraocular pressure (IOP) monitor that is fully wireless and implantable. Major benefits of an active IOP monitoring device include the potential to operate independently from an external device for extended periods of time and the possibility of developing a closed-loop monitoring and treatment system. The fully wireless operation is based off using gigahertz-frequency electromagnetic wave propagation, which allows for an orientation independent transfer of power and data over reasonable distances. Our system is comprised of a micro-electromechanical systems (MEMS) pressure sensor, a capacitive power storage array, an application-specific integrated circuit designed on the Texas Instruments (TI) 130 nm process, and a monopole antenna all assembled into a biocompatible liquid-crystal polymer-based tadpole-shaped package.

A microscale optical implant for continuous in vivo monitoring of intraocular pressure

“…Such measurements can only be obtained for up to 24 h because of side complications that accompany long-term use [41][42][43] . To overcome the aforementioned limitations, implants based on radio-frequency (RF) technologies have been used to monitor endovascular pressure 44 , intracranial pressure (ICP) 45,46 , and IOP [47][48][49][50][51][52][53][54][55][56][57][58] . The typical size of these implants ranges from a millimeter to a few centimetres.…”

MBus: A Fully Synthesizable Low-power Portable Interconnect Bus for Millimeter-scale Sensor Systems

“…This design approach is in contrast to the modularity that has characterized embedded system design and enabled it to address a highly diverse application space. The miniature sensor node application space is similarly diverse, ranging from implantable medical monitors [4][5][6] to nearly invisible surveillance [7]. Hence, a modular design approach that enables extensive reuse of chip modules is a key to fully address its application space.…”

Next generation RFID telemetry design for biomedical implants.

“…Some of the wireless implantable systems that have recently been developed include wireless systems to record neural activity [2], continuously monitor blood glucose levels [5], monitor cardiovascular pressure [6], and monitor intraocular pressure [7]. The first two systems both make use of inductive coupling for power transfer and data communications while the latter two systems use RF energy for powering and data transfer.…”

“…They were not able to develop a fully integrated system that is able to provide enough power for the rest of the circuit to operate. Chow et al also developed an implantable system for measuring intraocular pressure [7] as shown in Figure 8 mm of pork tissue, but were only able to achieve an operating range of 1.5 cm. A block diagram of the implant is shown in Figure 9.…”

“…Multistage rectifier/multiplier designs of both Greinacher and Dickson topologies were implemented using Schottky diodes and diode connected NMOS transistors and capacitors. The number of stages was initially limited to four since increasing the number of stages can lead to lower output voltages due the current drain of later stages [7]. Both of the topologies and implementations have successfully been used by others but they all made use of specialized processes and technologies that offered lower voltage operation [16,17,23].…”