Visible blind 4H-SiC UV detectors were investigated with respect to radiation hardness since they can find applications in the aerospace field. Effects of ion irradiation on their response were studied by monitoring the spectral response as a function of irradiation beam energy and dose. The devices irradiated by 1, 4, and 10MeV Si+-ion beam show a change of the response depending on the ion irradiation energy. The unexpected huge optical effect, compared to the negligible influence on reverse bias leakage current, was correlated to the nature of irradiation induced damage and to its location inside the optical active device layer.