**Question:** All of the following drugs are associated with corneal deposition except: September 2009

A. Prednisolone
B. Propranolol
C. Cyclopentolate
D. Atropine

**Core Concept:**

Corneal deposition is a potential side effect of certain medications when they accumulate on the cornea, the transparent outer layer of the eye. This can lead to symptoms like ocular irritation, photophobia, and vision impairment. Corneal deposition is mainly observed with drugs that are lipophilic, have a high molecular weight, or are poorly soluble in aqueous media.

**Why the Correct Answer is Right:**

Drugs associated with corneal deposition usually have the following characteristics:

1. Lipophilic: Prednisolone (A) is a lipophilic steroid, which is why it can accumulate on the cornea and cause side effects like ocular irritation and photophobia.
2. High molecular weight: Propranolol (B) is a low molecular weight beta-blocker, making it less likely to cause corneal deposition compared to other beta-blockers.
3. Poorly soluble in aqueous media: Cyclopentolate (C) is a mydriatic agent with poor solubility in aqueous media, which increases the risk of corneal deposition.
4. High molecular weight: Atropine (D) is a low molecular weight anticholinergic drug; thus, it is less likely to cause corneal deposition compared to other anticholinergic agents.

**Why Each Wrong Option is Incorrect:**

1. Prednisolone (A) is a lipophilic steroid with high molecular weight and poor solubility in aqueous media, making it prone to cause corneal deposition.
2. Propranolol (B) is a low molecular weight beta-blocker, which reduces the risk of corneal deposition when compared to other beta-blockers with higher molecular weight.
3. Cyclopentolate (C) is a mydriatic agent with high molecular weight and poor solubility in aqueous media, increasing the risk of corneal deposition.
4. Atropine (D) is a low molecular weight anticholinergic drug, which lowers the risk of corneal deposition when compared to other anticholinergic agents with higher molecular weight.

**Core Concept Explanation:**

The correct answer, atropine (D), is a low molecular weight anticholinergic drug, which reduces the risk of corneal deposition due to its low molecular weight. Atropine is used to dilate the pupil, and its low molecular weight allows it to diffuse across the cornea more easily and distribute uniformly, reducing the risk of corneal deposition.

**Why Each Wrong Option is Incorrect:**

1. Prednisolone (A) is a lipophilic steroid with high molecular weight and poor solubility in aqueous media, increasing the risk of corneal deposition.
2. Propranolol (B) is a low molecular weight beta-blocker, which increases