An 81-year-old patient with glaucoma is given a cholinergic agonist eye drop. What is the mechanism used to lower intraocular pressure?

• A. By decreasing production of intraocular fluid. 
• B. By constricting the pupils, which decreases outflow of intraocular fluid.  
• C. By dilating the pupils, which decreases outflow of intraocular fluid.  
• D. By constricting the pupils, which increases outflow of intraocular fluid.  

Answer: (D)

Verified step by step guidance

1. Understand that glaucoma is a condition characterized by increased intraocular pressure (IOP) due to impaired drainage or overproduction of aqueous humor (intraocular fluid).
2. Recognize that cholinergic agonists mimic the action of acetylcholine, stimulating the parasympathetic nervous system.
3. Know that cholinergic agonists cause constriction of the pupil (miosis) by stimulating the sphincter pupillae muscle.
4. Understand that pupil constriction leads to opening of the trabecular meshwork, which facilitates increased outflow of aqueous humor from the anterior chamber of the eye.
5. Conclude that the mechanism by which cholinergic agonists lower intraocular pressure is by increasing the outflow of intraocular fluid through pupil constriction, not by decreasing its production.