Optical polarimetry applied to the development of a noninvasive in vivo glucose monitor
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abstract
The application of optical polarimetry, using the anterior chamber of the eye as the sensing site, is being investigated as a potential method to develop a noninvasive physiological glucose monitor. Common questions currently associated with the use of polarimetry for noninvasive glucose detection include: `is polarimetry specific enough to elucidate glucose concentration in the presence of other optically active components?,' `if the eye is proposed as the sensing site, is the time delay between blood and aqueous humor glucose concentrations small enough to make the development of such a sensor feasible (i.e. useful to a diabetic)?,' and lastly `what are the issues currently hindering in vivo polarimetric glucose measurements?.' In our investigation, we attempt to address these questions. First, we present results characterizing the optical rotatory dispersion of the main optically active analytes found within the aqueous humor of the eye including, glucose, albumin, and ascorbic acid. This information is used conjunction with multiple linear regression to demonstrate how multispectral polarimetry can be used to minimize glucose prediction error in samples containing varying physiological concentrations of glucose and albumin. For this multispectral study, a novel dual wavelength (532 nm and 635 nm) polarimeter was designed and constructed. This sensor is novel in that it provides simultaneous measurements using a 532 nm laser in an open-loop configuration and a 635 nm laser in a closed-loop configuration. In addition, we present in vivo results using New Zealand White rabbits that indicate the time delay between blood and aqueous humor glucose levels is below ten minutes. Lastly, we provide preliminary in vivo polarimetric results and discuss the main issues currently hindering the measurement of glucose.
