Your pupils dilate when you see the person you are attracted to. Because the nervous system controls the muscles of the irises, the response of the nervous system to different stimuli results in involuntary pupil dilation. Another commonly cited reason the pupils dilate is in response to excitement or sexual arousal. When a person sees something or someone they find very attractive, their eyes may dilate.
My bf asked why my eyes were so dilated one day.. Now i know why