Final answer:
A nurse-administered agent that causes pupillary constriction is identified as a miotic. Miotics like pilocarpine constrict the pupil by targeting muscarinic receptors, which is opposite to the effect of mydriatics that dilate the pupil by simulating the sympathetic nervous system.
Step-by-step explanation:
The nurse administers an agent that causes the pupil to contract, which is identified as a miotic. This type of medication includes drugs like pilocarpine, which is a muscarinic agonist that constricts the pupil by acting on the smooth muscle of the iris and reduces intraocular pressure associated with glaucoma. In contrast, mydriatics like phenylephrine dilate the pupil by mimicking the action of the sympathetic nervous system.
In the case of poisoning by agents like atropine, pilocarpine can act as an antidote by reversing the effects of muscarinic antagonists that block the receptors and lead to dilation. The clinical applications of miotics extend beyond simple pupil constriction to therapeutic use in conditions such as glaucoma where drainage of aqueous humor is necessary. Hence, an eye drop that causes pupillary constriction would be considered a miotic and is an essential part of ocular therapeutics.