Optical near-field microscopy provides a variety of contrast mechanisms with possible nanometre resolution. For the first time we used optical absorption contrast in order to analyze ion-irradiated silicon films. A finely focused 17 keV Ne+ beam produces local amorphous areas with an enhanced optical extinction coefficient in a crystalline Si matrix. The photon scanning tunnelling microscope, a variant of the optical near-field microscopes, is very suitable to image the damaged areas with sufficient spatial resolution. The mechanism of the contrast origin is discussed.