瞳孔[doukou] pupil
瞳子[doushi] pupil
瞳を凝らす[hitomiwokorasu] to strain one's eyes
瞳孔拡張[doukoukakuchou] pupil dilation
瞳孔散大[doukousandai] dilation of the pupil

散瞳[sandou] mydriasis
縮瞳[shukudou] miosis
散瞳薬[sandouyaku] mydriatic agent
瞳孔縮小[doukoushukushou] pupil contraction