瞳どう孔こう括かつ約やく筋きんMeaningsNoun1. sphincter muscle of the pupil; sphincter pupillaeKanji used瞳pupil (of eye)孔small hole括tie a loop around約promise筋muscleComposed of瞳どう孔こうpupil (of the eye)Noun括かつ約やく筋きんsphincter (muscle); constrictorNoun