1. A non-invasive method for identifying the presence of and/or the concentration of a selected analyte in a subject, comprising: illuminating a selected region in the eye of a subject with an optical excitation beam, wherein the excitation beam wavelength is selected to generate a resonant Raman spectrum of the selected analyte; detecting a resonant Raman spectrum corresponding to the selected illuminated region of the eye; and identifying the presence, absence and/or the concentration of the selected analyte in the subject based on said detecting step.