Previously, we proposed a polarimetric method, that exploits the Brewster-reflection with the final goal of application to the human eye (reflection off the eye lens) for non-invasive glucose sensing. The linearly polarized reflected light of this optical scheme is rotated by the glucose molecules present in the aqueous humor, thus carries the blood glucose concentration information. A proof-of-concept experimental bench-top setup is presented, applying a multi-wavelength true phase measurement approach and a rotating phase retarder as an analyzer to measure the very small rotation angles and the complete polarization state of the measurement light.
In this paper we present theoretical analysis to support the polarimetric approach for glucose detection in the human eye applying Brewster reflection off the ocular lens. The theoretical eye model of Navarro, which is based upon anatomical data, was used to perform ray-tracing, whereas the electromagnetic and polarization parameters of light propagation through the eye-media were calculated. The errors in glucose concentration determination due to refraction and deviation from the ideal optical path were calculated under different conditions. Effects of using incident linearly and circularly polarized light and variation of intersection condition of the incoming light beam with the anterior corneal surface were taken into consideration. Calculations were performed for a wide spectral range by applying dispersion curves for the eye-media. These simulations show the potential and the limits of the proposed optical approach.
An important task of in vivo polarimetric glucose sensing is to find an appropriate way to optically access the aqueous humor of the human eye. In this paper two different approaches are analyzed theoretically and applied to the eye model of Le Grand. First approach is the tangential path of Cote et al., and the second is a new scheme of this paper of applying Brewster reflection off the eye lens.
Optical methods represent the most promising techniques to perform non-invasive glucose detection. Glucose concentration in the aqueous humor closely mimics glucose levels in the blood and therefore non-invasive optical measurement of glucose can be performed by an optical beam crossing the eye anterior chamber. We propose a polarimetric method that exploits the Brewster-reflection of circularly polarized light on the lens of the eye. After reflection, the resulting linearly polarized light is subject to rotation by the glucose in the aqueous humor and thus carries the concentration information. A preliminary experimental setup, using glucose samples in a beaker, was realized and investigated.