A method and system for identifying a given geometrical feature of an optical component or semi-finished ophthalmic lens blank, where an optical component is made of an organic material that can emit light at an emission wavelength λe when being lighten at an illumination wavelength λi different from the emission wavelength λe, a surface of the optical component is illuminated with an incident light beam including at least light at the illumination wavelength but devoid from light at the emission wavelength, light emitted at the emission wavelength by the illuminated surface is collected to build an image of the surface, and the surface image is processed to apply metrics to compare the image with reference data specific to the given geometrical feature.