A client who has glaucoma is to have miotic eye drops instilled in both eyes. The nurse knows that the purpose of the medication is to:
A. Anesthetize the cornea
B. Dilate the pupils
C. Constrict the pupils
D. Paralyze the muscles of accommodation
Correct Answer: C. Constrict the pupils
Miotic eye drops constrict the pupil and allow aqueous humor to drain out of the Canal of Schlemm. Pilocarpine is a muscarinic acetylcholine agonist that is effective in the treatment and management of acute angle-closure glaucoma and radiation-induced xerostomia. Although not a first-line treatment for glaucoma, it is useful as an adjunct medication in the form of ophthalmic drops.
Option A: The cornea and conjunctiva can be anesthetized by drops of any of the local anesthetics. Bupivacaine, for example, is effective as an eyedrop. Bupivacaine is a potent local anesthetic with unique characteristics from the amide group of local anesthetics, first discovered in 1957. Local anesthetics are used in regional anesthesia, epidural anesthesia, spinal anesthesia, and local infiltration. Local anesthetics generally block the generation of an action potential in nerve cells by increasing the threshold for electrical excitation.
Option B: The eye doctor may dilate the pupils with a special medication called a mydriatic, so they can see the inside of the eye during a slit lamp test. Typically, mydriasis reverses within 4 to 8 hours. However, it may take 24 hours for the mydriatic effect to wear off in some individuals. Weaker strength may cause mydriasis with little cycloplegia.
Option D: Scopolamine ophthalmic is an anticholinergic agent that blocks constriction of sphincter muscle of iris and ciliary body muscle, which, in turn, results in mydriasis (dilation) and cycloplegia (paralysis of accommodation). Scopolamine competitively inhibits G-protein coupled post-ganglionic muscarinic receptors for acetylcholine and acts as a nonselective muscarinic antagonist, producing both peripheral antimuscarinic properties and central sedative, antiemetic, and amnestic effects.