Which is the shoest acting mydriatic: March 2004
**Core Concept**
The question is testing knowledge of mydriatic agents used in ophthalmology, specifically their duration of action. Mydriatics are medications that cause pupil dilation, and their pharmacological properties determine their clinical utility.
**Why the Correct Answer is Right**
The correct answer is **Tropicamide**, which is an anticholinergic mydriatic agent. It works by inhibiting the muscarinic receptors in the iris sphincter muscle, leading to pupil dilation. Tropicamide has a short duration of action, typically lasting around 4-6 hours, making it an ideal choice for diagnostic purposes in ophthalmology. Its quick onset and short duration allow for rapid pupil dilation and subsequent assessment of the fundus.
**Why Each Wrong Option is Incorrect**
* **Option A:** **Cyclopentolate** is a longer-acting anticholinergic mydriatic agent, with a duration of action typically lasting 24 hours. It is often used for diagnostic purposes in pediatric patients.
* **Option B:** **Atropine** is a longer-acting anticholinergic mydriatic agent, with a duration of action typically lasting 7-14 days. It is often used for therapeutic purposes, such as treating uveitis or preventing postoperative complications.
* **Option D:** **Pilocarpine** is a miotic agent, which causes pupil constriction rather than dilation. It is often used to treat conditions such as glaucoma.
**Clinical Pearl / High-Yield Fact**
When choosing a mydriatic agent, it is essential to consider the duration of action and the specific indication for use. Tropicamide's short duration of action makes it an ideal choice for diagnostic purposes, while longer-acting agents like atropine may be more suitable for therapeutic purposes.
**Correct Answer: C. Cyclopentolate is incorrect as the correct answer is Tropicamide.