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.

1 - 28 . (canceled)  
   
   
       29 . A method for measuring blood glucose level in an individual, comprising: 
 illuminating a portion of the retina positioned outside the normal retinal vasculature to alter the concentration of a visual pigment in the portion of the retina;    measuring a rate of change of the visual pigment concentration in the portion of the retina outside the retinal vasculature; and    determining the blood glucose level of the individual based on the measured rate of change of visual pigment concentration.    
   
   
       30 . The method according to  claim 29  wherein the portion of the retina positioned outside of the normal retinal vasculature comprises more cones than rods.  
   
   
       31 . The method according to  claim 29  wherein the portion of the retina positioned outside of the normal retinal vasculature comprises the fovea.  
   
   
       32 . The method according to  claim 31  wherein the portion of the retina positioned outside of the normal retinal vasculature comprises the fovea centralis.  
   
   
       33 . The method according to  claim 29  wherein illuminating a portion of the retina comprises illuminating a portion of the retina with a light having a wavelength range that includes the active absorption band of a retinal visual pigment.  
   
   
       34 . The method according to  claim 29  wherein illuminating a portion of the retina comprises illuminating a portion of the retina with a light having a wavelength range that includes the active absorption band of more than one retinal visual pigment.  
   
   
       35 . The method according to  claim 29  wherein illuminating a portion of the retina comprises illuminating a portion of the retina with a light having a wavelength range that includes the active absorption band of more than one cone visual pigment.  
   
   
       36 . The method according to  claim 29  wherein illuminating a portion of the retina comprises illuminating a portion of the retina with a light having a wavelength range that includes the active absorption band of one cone visual pigment and one rod visual pigment.  
   
   
       37 . The method according to  claim 29  wherein illuminating a portion of the retina comprises illuminating a portion of the retina with a light having a wavelength consistent with a wavelength known to activate rhodopsin in areas of the fovea illuminated by the light.