 This is the pupillary light reflex, which is an important test of brainstem function.Furthermore, the pupil will dilate if a person sees an object of interest.If the drug pilocarpine is administered, the pupils will constrict and accommodation is increased due to the parasympathetic action on the circular muscle fibers, conversely, atropine will cause paralysis of accommodation (cycloplegia) and dilation of the pupil.