Design of an Optical Pressure Measurement System for Intraocular Pressure Monitoring

• Published in: IEEE sensors journal 2018-01, Vol.18 (1), p.61-68
• Main Authors: Phan, Alex, Phuong Truong, Trumpp, Julian, Talke, Frank E.
• Format: Article
• Language: English
• Subjects: Biocompatibility; Biomedical optical imaging; Cornea; Diaphragms; Glass; Glass substrates; Glaucoma; Interference fringes; Interferometry; Intraocular pressure; Optical interferometry; Optical sensors; Optical variables measurement; Pressure measurement; Pressure sensors; Sensors; Silicon nitride; Silicon substrates
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2017.2767539

This paper studies the design and application of an interferometric sensor system intended for measuring intraocular pressure. The system consists of a hermetically sealed, biocompatible, wireless, and powerless interferometric pressure sensor and a portable handheld reader. The interferometric pressure sensor consists of a 200 nm silicon nitride diaphragm, a 10~\mu \text{m} SU-8 spacer, and a 200~\mu \text{m} glass substrate. As monochromatic light is directed towards the sensor cavity, interference fringes between the silicon nitride diaphragm and the glass substrate form as a function of the applied pressure. In-vitro measurements show pressure in the range of 0-60 mmHg can be determined reliably with an accuracy of ±0.3 mmHg, while ex-vivo experiments using rabbit cornea showed an accuracy of ±0.6 mmHg. The resolution of the sensor is 0.2 mmHg. These results demonstrate the ability of the system to measure small changes in pressure, including intraocular pressure of glaucoma patients.