Non-invasive measurement of blood analytes using photodynamics

Abstract

The determination of blood glucose in an individual is carried out by projecting illuminating light into an eye of the individual to illuminate the retina with the light having wavelengths that are absorbed by rhodopsin and with the intensity of the light varying in a prescribed temporal manner. The light reflected from the retina is detected to provide a signal corresponding to the intensity of the detected light, and the detected light signal is analyzed to determine the changes in form from that of the illuminating light. For a biased sinusoidal illumination, these changes can be expressed in terms of harmonic content of the detected light. The changes in form of the detected light are related to the ability of rhodopsin to absorb light and regenerate, which in turn is related to the concentration of blood glucose, allowing a determination of the relative concentration of blood glucose. Other photoreactive analytes can similarly be determined by projecting time varying illuminating light into the eye, detecting the light reflected from the retina, and analyzing the detected light signal to determine changes in form of the signal due to changes in absorptivity of a photoreactive analyte.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation of prior application Ser. No. 10 / 012,902, filed Oct. 22, 2001, which claimed priority from provisional application No. 60 / 318,850, filed Sep. 13, 2001, which are incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention pertains to the field of non-invasive in vivo measurement of blood analytes. BACKGROUND OF THE INVENTION [0003] The measurement of blood glucose by diabetic patients has traditionally required the drawing of a blood sample for in vitro analysis. The blood sampling is usually done by the patient himself as a finger puncture, or in the case of a child, by an adult. The need to draw blood for analysis is undesirable for a number of reasons, including discomfort to the patient, resulting in many patients not testing their blood as frequently as recommended, the high cost of glucose testing supplies, and the risk of infection with repeated skin punctures. [0004] Many of th...

AI Technical Summary

Benefits of technology

"The present invention is a non-invasive and accurate method for measuring blood glucose levels using a handheld instrument. The instrument measures the regeneration rate of rhodopsin, which is dependent on blood glucose concentration. The method uses a light source that is directed onto the cones of the retina, which are responsible for central and color vision. The light source is filtered to remove the primary frequency, leaving higher order harmonics of the fundamental as the input into the analysis system. The invention can also be used to measure other photoreactive analytes such as bilirubin, which is elevated in newborns and causes jaundice. The instrument is calibrated for each patient and the data is sent to a central computer for processing and display. The technical effects of the invention include the accuracy of blood glucose measurement and the non-invasive and safe method of monitoring diabetes."

Problems solved by technology

The need to draw blood for analysis is undesirable for a number of reasons, including discomfort to the patient, resulting in many patients not testing their blood as frequently as recommended, the high cost of glucose testing supplies, and the risk of infection with repeated skin punctures.

As a result of the discomfort, many of these patients do not test as often as is recommended by their physician, with the consequence of poor blood glucose control.

This poor control has been shown to result in increased complications from this disease.

Prior efforts have been unsuccessful in the quest for a sufficiently accurate, non-invasive blood glucose measurement.

These efforts have been largely unsuccessful primarily due to the variability of absorption and scatter of the electromagnetic energy in the tissues.

To date, these efforts have not been successful for a variety of reasons.

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