A method is provided that includes discriminating an autofluorescence (AF) response of a lens tissue of an eye due to a current level of 2-(2-furoyl)-4(5)-furanyl-1H-imidazole (FFI) in the lens tissue by interrogating a lens tissue of an eye along a visual axis of the eye by activating an illuminator for a select time to produce interrogating irradiation having a peak wavelength of 425 nm to 460 nm, the illuminator comprising at least one light source and a focal lens positioned with respect to the light source. The method also includes obtaining at least one image of the autofluorescence response of the lens tissue from a detector, the detector including a digital camera unit, analyzing the at least one image to determine a total autofluorescence index of the lens tissue, and determining a current level of FFI in the lens tissue based, at least in part, on the total autofluorescence index.