Title

A new approach to monitoring glucose concentrations based on reflection of polarized light from a liquid/lens interface and detection by an improved, closed-loop, optical polarimeter

Date of Completion

January 1998

Keywords

Health Sciences, Rehabilitation and Therapy|Engineering, Biomedical|Engineering, Electronics and Electrical

Degree

Ph.D.

Abstract

The purpose of this study is three-fold: to validate the hypothesis that the well-known optics of the human eye will allow linearly polarized light (LPL) to be reflected from the interface between the aqueous humor and the lens of the eye; to validate the hypothesis that rotation caused by an optically active medium will be maintained upon reflection from a dielectric surface; and to show that a sensitive polarimeter can reliably measure the rotation of reflected light caused by concentrations of D-glucose solution in front of a reflecting surface.^ Over time, much effort and funding has been invested in the attempt to use the human eye as a window to measure systemic glucose levels, which would be a significant advancement in the treatment of diabetes. The method sought after is to measure the rotation of LPL as it passes through the aqueous humor, containing optically active D-glucose. Research has developed systems that can measure these small angles in transmission mode. However, to be implemented in vivo, the light has to be reflected off an interface inside the eye. The current research was based on the belief that this could be accomplished by reflecting the light off the lens. To validate this, the optics of the eye had to be shown capable of allowing a light beam to be passed into the eye, reflected from the lens, and sensed on exit. Nothing in the literature validates the feasibility of using such a method on the human eye.^ It was shown that it is possible to measure rotation of LPL caused by an optically active medium in front of a dielectric, reflecting interface at certain angles of incidence. It is believed that this is a new finding. Furthermore, it was shown that the geometry of the eye allows for using a reflection-mode technique. The results suggest that with additional refinement, this method and system could be developed into a robust, noninvasive glucometer. An end product is envisioned in the form of a hand-held device to take fast, painless, noninvasive glucose levels; the present research has made a significant contribution in that direction. ^