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Alex Phan, Phuong Truong, Andrew Camp, Robert N Weinreb, Frank Talke; In vivo Investigation of an Interferometric Pressure Measurement System for Glaucoma Management. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3481.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate an optical pressure measurement system for frequent and direct measurement of intraocular pressure (IOP) in vivo (rabbits).
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 µm 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. Six 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 (Fig. 1). IOP measurements were successfully obtained using the portable DSLR handheld reader (Fig. 2 and Fig. 3).
In vivo studies demonstrate biocompatibility of the IOP sensor and prove feasibility of the IOP measurement system. Once implanted in rabbits, the sensor was used to readily measure IOP accurately and repeatedly.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig. 1. (a) IOP sensor was integrated to IOL and implanted during cataract surgery (b) Appearance of interference pattern when monochromatic light is directed at the sensor.
Fig. 2. Fringe pattern was analyzed to obtain the deflection of the membrane and determine the intraocular pressure.
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