Which indirect cholinesterase inhibitor is used to decrease intraocular pressure?

• A. Edrophonium
• B. Donazepil
• C. Pilocarpine
• D. Echothiophate

Answer: (D)

Indirect cholinesterase inhibitors raise acetylcholine levels in the eye by blocking its breakdown, increasing muscarinic stimulation that promotes ciliary muscle contraction and enhances aqueous humor outflow, thereby lowering intraocular pressure. Echothiophate is an organophosphate that inhibits acetylcholinesterase with a long-lasting effect in the eye, making it the classic indirect agent used to reduce IOP.

The other options don’t fit the mechanism: edrophonium is a short-acting AChE inhibitor used mainly for diagnostic testing; donepezil is a central AChE inhibitor for Alzheimer's disease; pilocarpine is a direct muscarinic agonist (not an AChE inhibitor) that lowers IOP by stimulating receptors directly rather than by inhibiting acetylcholine breakdown.