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.
