Measurement of the Glucose Transport Time Delay Between the Blood and Aqueous Humor of the Eye for the Eventual Development of a Noninvasive Glucose Sensor

Abstract

In the recent past, several noninvasive optically based methods have been proposed for physiologic glucose sensing. One proposed optical sensing site has been the eye, which, due to its unique optical properties, can be considered as a transparent optical window into the body. In particular, the aqueous humor within the anterior chamber of the eye has been shown to contain glucose levels correlated to those of blood. Concern, however, has been expressed that using the aqueous humor solution as a measure of blood glucose may be problematic due to the potential transport time delay between the blood and the aqueous humor glucose concentrations. This investigation was performed to measure the transport time delay in a rabbit model. The time delay between the blood and aqueous humor glucose concentrations was measured invasively in five New Zealand White rabbits over a series of weeks. An anesthesia protocol containing the drug Xylazine was used to elevate the blood glucose levels to a level commonly seen in diabetic patients. The difference between the glucose peak location times occurring in the blood and aqueous humor glucose response was measured and defined as the transport time delay. The average transport time lag was measured to be under 5 min. This measured time delay indicates that, indeed, the eye could potentially be used as a sensing site for indirect blood glucose measurements and may eventually aid the development of a noninvasive glucose sensor due to its unique optical properties compared to other biological tissues.