Non-invasive measurement of blood analytes using photodynamics

• US 20040147820A1
• Filed: 08/15/2003
• Published: 07/29/2004
• Est. Priority Date: 09/13/2001
• Status: Active Grant

• Current Assignee: Fovioptics Incorporated
• Original Assignee: Fovioptics Incorporated
• Inventors: Routt, Wilson, Rice, Mark J.
• Granted Patent: US 6,889,069 B2
• Time in Patent Office: Days
• US Class Current: 600/318
• CPC Class Codes: A61B 3/12 for looking at the eye fundus, e.g. ophthalmoscopes A61B3/13 takes precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14558 by polarisation

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.

Claims

1. A method for use in the determination of blood glucose in an individual comprising:

(a) projecting illuminating light into an eye of the individual to illuminate the retina in the eye, the light having wavelengths that are absorbed by rhodopsin with the intensity of the light varying in a selected temporal manner;

(b) detecting the light reflected from the retina of the eye to provide a detected light signal corresponding to the intensity of the detected light; and

(c) analyzing the detected light signal to determine the distortion of the detected light relative to the illuminating light.

2. The method of claim 1 wherein the intensity of the illuminating light varies periodically at a selected frequency and the detected light signal is analyzed to determine the magnitude of a harmonic or harmonics of the frequency at which the illuminating light varies.

3. The method of claim 2 wherein the illuminating light is varied sinusoidally.

4. The method of claim 3 wherein the illuminating light is varied sinusoidally with the intensity of the illuminating light never reaching zero intensity.

5. The method of claim 3 wherein the frequency at which the illuminating light is varied is in the range of 0.1 to 200 Hz.

6. The method of claim 2 wherein the steps (a), (b) and (c) are repeated sequentially with at least two different frequencies of variation of the illuminating light.

7. The method of claim 2 wherein the steps (a), (b) and (c) are repeated sequentially three times at three different frequencies of variation of the illuminating light.

8. The method of claim 7 wherein the three different frequencies of variation of the illuminating light are 1 Hz, 3 Hz and 10 Hz.

9. The method of claim 1 wherein the illuminating light contains wavelengths at least in the range of 500 nm to 600 nm.

10. The method of claim 2 further including low pass filtering the detected light signal to remove the component of the signal at the frequency at which the illuminating light is varied before the step of analyzing the detected signal.

11. The method of claim 2 further including determining the blood glucose concentration from the magnitude of the harmonic or harmonics in the detected signal.

12. The method of claim 1 wherein in the step of detecting the light reflected from the retina, the light detected is substantially only the light reflected from the fovea of the retina.

13. A method for use in the determination of a photoreactive blood analyte in an individual comprising:

(a) projecting illuminating light into an eye of the individual to illuminate the retina in the eye, the light having wavelengths that are absorbed by the photoreactive analyte with the intensity of the light varying periodically at a selected frequency;

(b) detecting the light reflected from the retina of the eye to provide a detected light signal corresponding to the intensity of the detected light; and

(c) analyzing the detected light signal to determine a variation in the signal resulting from interaction of the illuminating light with the photoreactive analyte.

14. The method of claim 13 wherein in the step of analyzing the detected light signal to determine a variation, the variation that is determined is the magnitude of a harmonic or harmonics of the frequency at which the illuminating light varies.

15. The method of claim 13 wherein the illuminating light is varied sinusoidally.

16. The method of claim 15 wherein the illuminating light is varied sinusoidally with the intensity of the illuminating light never reaching zero intensity.

17. The method of claim 15 wherein the frequency at which the illuminating light is varied is in the range of 0.1 to 200 Hz.

18. The method of claim 13 wherein the steps (a), (b) and (c) are repeated sequentially with at least two different frequencies of variation of the illuminating light.

19. The method of claim 13 wherein in the step of detecting the light reflected from the retina, the light detected is substantially only the light reflected from the fovea of the retina.

20. The method of claim 13 further including low pass filtering the detected light signal to remove the component of the signal at the frequency at which the illuminating light is varied before the step of analyzing the detected signal.

21. Apparatus for use in determination of blood glucose in an individual comprising:

(a) means for projecting illuminating light into an eye of an individual to illuminate the retina in the eye with the light having wavelengths that are absorbed by rhodopsin and with the intensity of the light varying periodically at a selected frequency; and

(b) means for detecting the light reflected from the retina of the eye and providing a detected light signal corresponding to the intensity of the detected light.

22. The apparatus of claim 21 further including a means for analyzing the detected light signal to determine the magnitude of a harmonic or harmonics of the frequency at which the illuminating light varies.

23. The apparatus of claim 21 wherein the means for projecting illuminating light varies the intensity of the illuminating light sinusoidally with the intensity of the illuminating light never reaching zero intensity.

24. The apparatus of claim 23 wherein the frequency at which the illuminating light is varied is in the range of 0.1 to 200 Hz.

25. The apparatus of claim 21 wherein the illuminating light contains wavelengths at least in the range of 500 nm to 600 nm.

26. The apparatus of claim 21 wherein the means for detecting the light reflected from the retina detects substantially only the light reflected from the fovea of the retina.

27. The apparatus of claim 21 further including a low pass filter receiving the detected light signal to remove the component of the signal at the frequency at which the illuminating light is varied.

28. The apparatus of claim 21 further including means for analyzing the detected light signal to determine the magnitude of a harmonic or harmonics of the frequency at which the illuminating light varies and means for determining the blood glucose concentration from the magnitude of the harmonic or harmonics in the detected signal.