Noninvasive monitoring of glucose concentration through the aqueous humor

Purpose:Development of a new optical sensor for measuring blood glucose levels noninvasively to replace the current finger-prick method routinely used by diabetics. Methods:We have developed a new optical scheme for a polarimetric-based glucose sensor. Such a sensor is intended to noninvasively measure the glucose content of the aqueous humor, which is highly correlated to the blood glucose concentration in the body. The polarimetric measurement method is based upon optical activity of glucose, i.e., the plane of polarization of a polarized light beam is rotated when propagating through a glucose solution. The amount of polarization rotation is proportional to the glucose concentration, which therefore can be determined. Our new optical scheme applies Brewster reflection of incident circularly polarized light off the eye lens. The incoming light is not affected by optical activity. However, the back reflected linearly polarized light is rotated while crossing the aqueous humor of the eye. From this polarization rotation of the reflected light the glucose concentration in the aqueous humor can be determined. Results:In this proof-of-concept study the linearity between glucose concentration and polarization rotation is investigated with glucose concentrations ranging from 0 to 1000 mg/dl. The obtained data show a correlation coefficient of 0.986. Further, we have tested our approach on a model of the human eye, which has been designed in our lab. In this eye model the cornea has been modeled by a contact lens, the aqueous humor by solutions of glucose in distilled water, and the crystallin lens by a lens implant. Conclusions:The results show good linearity of the measurement system. However, detailed experimental work is needed to demonstrate its full applicability in human patients.