Patent ID: 7308293
Filing Date: 2007-12-11
Classification: A61B

Abstract:
1. A method of determining the concentration of a substance in an eye, the eye having a cornea, a pupil, an iris, a lens, a liquid, and a retina, the method comprising: providing a nearly parallel measurement light beam having a first wavelength at which the substance has a non-zero first absorption coefficient; providing a nearly parallel reference light beam having a second wavelength at which the substance has a second absorption coefficient which is substantially equal to zero; irradiating the retina with the measurement light beam, thereby passing the measurement light beam through the cornea, the pupil, the lens, and the liquid; irradiating the retina with the reference light beam, thereby passing the reference light beam through the cornea, the pupil, the lens, and the liquid; reflecting at least a portion of the measurement light beam from the retina and through the liquid, the lens, the pupil, and the cornea, thereby producing a measurement retro-reflected light beam having the first wavelength; reflecting at least a portion of the reference light beam from the retina and through the liquid, the lens, the pupil, and the cornea, thereby producing a reference retro-reflected light beam having the second wavelength; providing a detector adapted to generate a measurement signal in response to being irradiated by light having the first wavelength and to generate a reference signal in response to being irradiated by light having the second wavelength, the detector located at a distance of at least 100 mm from the eye; irradiating the detector with the measurement retro-reflected light beam; irradiating the detector with the reference retro-reflected light beam; and determining the concentration of the substance in the eye in response to the measurement signal and the reference signal from the detector.