ðɪs ɹˈoʊl ɪz vˈɛɹi ɪmpˈoːɹtənt fɔːɹ tˈuː mˈeɪn ɹˈiːzənz, fˈɜːst, tʊ ɪmpɹˈuːv ðə kwˈɔlᵻɾi ʌvðɪ ˈɑːptɪkəl sˈɪstəm, sˈɛkənd, lˈaɪt ɪz ɹˌeɪdɪˈeɪʃən, ænd ɪɾ ɪz kˈɑːnsəntɹˌeɪɾᵻd baɪ ɐ lˈɛnz ˌɑːntʊ ðə sˈɛlz ʌvðə mˈækjʊlə, ɹɪzˈʌltɪŋ ɪn ɐ stɹˈɔŋ kˌɑːnsəntɹˈeɪʃən ʌv fˈoʊɾoʊˈɑːksɪdətˌɪv ˈɛnɚdʒi.
This role is very important for two main reasons, first, to improve the quality of the optical system, second, light is radiation, and it is concentrated by a lens onto the cells of the macula, resulting in a strong concentration of photo-oxidative energy.