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.
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.