Which statement is correct about PS effects of anticholinergic agents?

• A. Atropine breaks PS, while homatropine prevents PS.
• B. Atropine prevents PS, while homatropine breaks PS.
• C. Pilocarpine breaks PS, while tropicamide prevents PS.
• D. Edrophonium prevents PS, while pyridostigmine breaks PS.

Answer: (A)

Anticholinergic (parasympatholytic) agents block acetylcholine at muscarinic receptors in the eye, removing parasympathetic influence and causing pupil dilation and cycloplegia. Among common ophthalmic agents, atropine is the most potent and longest-acting muscarinic antagonist, producing a very robust parasympathetic blockade. Homatropine is also an antimuscarinic but is weaker and shorter acting.

Because of this potency difference, the statement that atropine breaks parasympathetic activity while homatropine prevents it best reflects their relative effects: atropine yields a more complete PS blockade, whereas homatropine produces a milder blockade.

The other options don’t fit because pilocarpine is a muscarinic agonist that enhances parasympathetic activity (not breaking it), and acetylcholinesterase inhibitors like edrophonium and pyridostigmine increase acetylcholine and thus boost parasympathetic effects (not prevent them). Tropicamide is also an antimuscarinic, but the pairing with pilocarpine makes that option incorrect.