One of the key requirements for optical switching apertures for ophtalmic, building and automobile glazing is long lived product. However, oxidation of a spirooxazine yields photoproducts such as oxindole derivatives, naphthoxazole, dihydro-2,6-quinolone and 1-N-formylimino-2-naphthoquinone devoid of photochromic activity, and limits the commercialisation of these useful systems. Achieving this long lived product can be provide by use of hindered amine light stabilizers (HALS). This paper describs the comportment of a spirooxazine irradiated in the presence of a HALS and the main stabilization mechanisms are discussed.