receiving detector output from at least one optical detector, the detector output being indicative of optical properties of light reflected or deflected from the respective multilayered tissue;

analyzing the received detector-output to determine spectral properties of the multilayered tissue; and

determining physical characteristics of the multilayered tissue by using multiple spectral models of the of the multilayered tissue comprising at least: a first model assuming a normal condition of the multilayered tissue and one or more additional models, assuming abnormal conditions of the multilayered tissue, each model being associated with different spectral properties of the multilayered tissue, wherein physical characteristics of the multilayered tissue are determined by hierarchal determination of a best-fit model from the multiple spectral models, based on determination of best-fit of the multilayered tissue to one of the spectral models,

wherein the determining of the physical characteristics of the multilayered tissue is done by comparing spectral properties of a reflected light to spectral properties of the first model and of the one or more additional models within at least one predefined wavelengths range in which spectral properties of the reflected light is distinctively different for different conditions of the multilayered tissue, and