Development of a MEMS device to continuously monitor glaucoma

Development of a MEMS device to continuously monitor glaucoma

Shankar, S 2006, Development of a MEMS device to continuously monitor glaucoma, Masters Thesis, School of Electrical and Computer Engineering, RMIT University.

Document type:	Thesis
Collection:	Theses

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Title	Development of a MEMS device to continuously monitor glaucoma
Author(s)	Shankar, S
Year	2006
Abstract	The objective of this thesis was to investigate the development of a micro-electromechanical system (MEMS) which can be implanted in the eye to provide continuous monitoring of glaucoma conditions. Current glaucoma monitoring involves taking laboratory based intra ocular pressure (IOP) measurements. The measurement of intraocular fluid flow and IOP parameters related to blockage formation in the eye require to be continuously monitored in Glaucoma. Making blockage related information available to patients could indicate the conditions leading to a blockage and help to improve glaucoma treatment and reduce the risk of permanent blindness. The specific aim of this research was to develop an implantable micro device capable of responding to the blockage of fluid flow in the eye. A mathematical model of the IOP dynamics in the eye, incorporating the IOP exponential decay phenomenon, was used to study the pressure changes that will occur in the eye due to glaucoma during external measurements. The mathematical model helped to analyse the principle behind IOP measurement and was extended to internal measurements by analysing time-based changes of variables integral to the process, such as eye rigidity, size, pressure, volume etc. The mathematical simulations helped to determine the physical requirements of an implantable micro device capable of increasing the IOP temporarily for the duration of a measurement. Finite element method analyses were conducted to determine the dimensions of a MEMS pressure sensor that could respond mechanically to the pressure changes initiated inside the eye by the micro device and convert the responses to electrically measurable units. The pressure resolution required of the MEMS pressure sensor was learned from the investigations and the electrical output indicative of the extent of glaucoma in an eye was also calculated. Integrating the intraocular dynamics and the MEMS pressure sensor responses constituted a mathematical model of the implantable micro system. The micro system model was tested for normal and adverse eye operating conditions to estimate the output based on various internal IOP measurements. The output that would be obtained from the implantable micro system was compared to responses from external measurements and found to be comparable. An overview of a comprehensive MEMS monitoring system including the micro device to increase the pressure within the eye, a MEMS pressure sensor, and powering and signal conditioning electronics was provided. A description of the technologies that could be used for the fabrication and packaging of the device and the sensor was also included at the end of the thesis along with a discussion on bio-compatibility and implanting issues. Thus the feasibility of combining a micro device and a micro sensor with powering and signal conditioning electronics to create an implantable MEMS system that can make continuous measurements which can indicate the onset of or an increase in blockage of the eye of a person with glaucoma is presented in the thesis.
Degree	Masters Thesis
Institution	RMIT University
School, Department or Centre	School of Electrical and Computer Engineering
Keyword(s)	Glaucoma IOP MEMS Implantable Continuous monitoring Anterior chamber Mathematical eye model

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