Effect of temperature, pH, and corneal birefringence on polarimetric glucose monitoring in the eye

Abstract

Over the last two decades polarimetry has been investigated as a noninvasive alternative for glucose monitoring in support of diabetic patients. In particular, the anterior chamber of the eye containing the fluid known as the aqueous humor has been confirmed to be the optimal sensing site for polarimetric glucose measurements due to its reasonable pathlength (1 cm), low scatter, and minimal depolarization index. In essence, the eye can be thought of as an optical window into the body. In this paper, we will first introduce the key challenges that must be overcome to make the use of polarized light in the eye a viable method for noninvasive glucose monitoring, summarize our work toward this endeavor, and then report on our latest research, namely, the effect of temperature, pH, and corneal birefringence on our polarimetric glucose monitoring system.

Modeling the corneal birefringence of the eye toward the development of a polarimetric glucose sensor

“…[12][13][14][15][16][17] Stanworth and Naylor proposed that the corneal birefringence for light passing normally though the cornea is small, but increases rapidly with increasing angle of incidence. 13 Bour and Lopes Cardozo proposed a method to measure the retardation as a function of the point of incidence on the pupil plane, and observed that corneal retardation has its slow axis along the tangent to the cornea, and that its magnitude increases with increasing eccentricity of the posterior corneal surface.…”

Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

“…The use of real-time feedback is essential, since the ultimate application of this technique is to minimize the effect of timevariant corneal birefringence in the eye. In a previous study from our group, 33 the primary motion-induced corneal birefringence artifact in a rabbit model was found to be mainly due to respiratory motion ͑1.5 Hz͒. Our feedback control mechanism took less than 300 ms to stabilize the system, which should be adequately fast to minimize the respiratory motion artifact.…”

GDx-MM: An Imaging Mueller Matrix Retinal Polarimeter

“…The optical activity arises because compounds are chiral (have a "handedness"); as a result the plane of polarization of linear polarized light is rotated as it traverses the aqueous solution. Baba has measured the rotation to be less than 14 millidegrees for a 1 cm pathlength [69]. This effect is extremely small and has never been considered in any retinal polarization studies.…”

“…In addition to polarization effects in the cornea and lens, small effects have been found in the aqueous humor [68,69]. Primarily due to the presence of glucose, albumin, and ascorbic acid, but also due to the presence of at least 20 other compounds, the aqueous humor exhibits optical activity.…”