Non-invasive glucose measurement method and apparatus

Abstract

A glucose sensor to provide a non-invasive means of determining blood glucose which is of particular value in the diagnosis and treatment of diabetes. The patient's eye is illuminated with near-infrared radiation which passes into the eye through the cornea and the aqueous humor, is reflected from the iris and/or lens surface, and then passes out through the aqueous humor and cornea. The reflected radiation is collected and detected by a near-infrared sensor which measures the reflected energy in one or more wavelength bands. Comparison of the reflected energy with the source energy provides a measure of the spectral absorption by the eye which is characteristic of the composition of the cornea, the aqueous humor, and the other structures within the eye through which the energy is transmitted or from which it is reflected. In particular, the level of glucose in the aqueous humor is a function of the level of glucose in the blood so that non-invasive determinations of blood glucose may be obtained by suitable calibration relating the measured spectral absorption of the aqueous humor to the measured blood glucose level. To obtain specificity and accuracy, the spectral data at several or many wavelengths may be utilized with a multivariate calibration and prediction process to separate the glucose information from the spectral influences of interfering substances, such as water, which also absorb the near-infrared radiation within the wavelength region utilized for the measurement. The system includes a computer for processing the spectral data and a display for readout of the result.