Which drug would be most likely to cause mydriasis?

Which drug would be most likely to cause mydriasis?

• A. Atropine
• B. Pilocarpine
• C. Latanoprost
• D. Timolol

Answer: (A)

Mydriasis happens when the parasympathetic constriction of the pupil is blocked, allowing the pupil to stay dilated. Atropine does exactly that: it blocks muscarinic receptors on the iris sphincter muscle, so acetylcholine can’t induce constriction. With the constrictor muscle inhibited, the pupil enlarges, and the ciliary muscle is also relaxed, causing cycloplegia. Pilocarpine does the opposite: it activates muscarinic receptors, causing the sphincter to contract and the pupil to constrict (miosis) and the eye to accommodate. Latanoprost lowers intraocular pressure by increasing uveoscleral outflow and can cause conjunctival redness or iris changes, but it doesn’t promote dilation. Timolol reduces aqueous humor production with no direct effect to dilate the pupil. So, the drug most likely to cause mydriasis is atropine.

Mydriasis happens when the parasympathetic constriction of the pupil is blocked, allowing the pupil to stay dilated. Atropine does exactly that: it blocks muscarinic receptors on the iris sphincter muscle, so acetylcholine can’t induce constriction. With the constrictor muscle inhibited, the pupil enlarges, and the ciliary muscle is also relaxed, causing cycloplegia.

Pilocarpine does the opposite: it activates muscarinic receptors, causing the sphincter to contract and the pupil to constrict (miosis) and the eye to accommodate. Latanoprost lowers intraocular pressure by increasing uveoscleral outflow and can cause conjunctival redness or iris changes, but it doesn’t promote dilation. Timolol reduces aqueous humor production with no direct effect to dilate the pupil.

So, the drug most likely to cause mydriasis is atropine.