Abstract: The present invention relates to devices and methodology for determining the variation in concentration of chromophores within an epithelial tissue. The devices comprise a means of illuminate the skin at one or more points and at wavelengths corresponding to specific chromophores. The device further comprises a detection means configured to detect the intensity of light remitted from the epithelial surface, a processing means configured to interpret image data sets obtained by the detection means and an output display to display the results or significance of the results. The invention further extends to a method of interpreting the distribution of chromophores within a lesion of an epithelial tissue. The method comprising the steps of illuminating an epithelial surface, determining the intensity of remitted light, analysing said intensity data to determine variation in the intensity across the lesion and providing an output corresponding to the extend of variation across the lesion.