169. in-vivo investigation of an interferometric pressure measurement system for glaucoma management

Department: Mechanical & Aerospace Engineering
Faculty Advisor(s): Frank E. Talke

Primary Student
Name: Alex Minh Giang Phan
Email: mgphan@ucsd.edu
Phone: 310-701-0252
Grad Year: 2018

Abstract
Glaucoma is one of the leading causes of irreversible blindness that affects millions of people worldwide. Eye pressure is associated with optic nerve damage and known to be the number one risk factor for glaucoma. The objective of this study is to evaluate an optical pressure measurement system for frequent and direct measurement of intraocular pressure (IOP) in vivo. The IOP measurement system consists of a miniaturized passive interferometric pressure sensor and a portable handheld optical reader. The sensor is 1.25 mm square and includes a deflecting silicon nitride membrane positioned 10 um above a rigid glass substrate. The membrane deflects as a function of pressure. When monochromatic light is directed towards the sensor cavity, interference fringes are formed and can be analyzed to determine IOP. Two sensors were tested in vitro to characterize the behavior in a pressure range from 0 mmHg to 100 mmHg. The sensors then were integrated onto an intraocular lens and implanted during cataract surgery in two rabbits. A portable optical handheld reader consisting of an internal beam splitter, a monochromatic light source, and a digital single-lens reflex (DSLR) camera was also developed to optically capture interference patterns from the sensor in any setting. The sensitivity and accuracy of the sensor in vitro was 30 nm/mmHg and +/-0.2 mmHg, respectively. Ten weeks post-implantation, the two New Zealand white rabbits continued to respond well to the implant with no significant inflammation, signs of infection, or protein deposition. The implanted sensors were clearly visible in both rabbit eyes. IOP measurements were successfully obtained using the portable DSLR handheld reader and compared with tonometry measurements. Overall, the results show a very promising approach to help monitor eye pressure in glaucoma patients. As a patient point-of-care technology, the proposed approach will enable patients to obtain accurate and more frequent measurements of their eye pressure at the convenience of their home. Frequent measurement data will equip ophthalmologists with the information necessary to make timely therapeutic interventions and improve treatment plans to preserve vision of glaucoma patients.

Industry Application Area(s)
Life Sciences/Medical Devices & Instruments | Materials | Ophthalmology

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