Ophthalmic Pharmacology Practice Questions

Q: A patient came with redness and pain, and you dilated the pupil to break the synechiae. Which drug was used, looking at this picture?

Atropine. ***Atropine*** - Atropine is a **muscarinic antagonist** that acts as a potent **cycloplegic** and mydriatic, essential for breaking **posterior synechiae** in acute iridocyclitis. - It provides prolonged **ciliary muscle paralysis**, which helps relieve the **ciliary spasm** and pain associated with anterior uveitis. *Phenylephrine* - Phenylephrine is an **alpha-adrenergic agonist** that causes pupil dilation through **iris dilator muscle contraction** but lacks cycloplegic effects. - Because it does not cause **ciliary muscle paralysis**, it is ineffective at relaxing the ciliary body to break synechiae compared to cycloplegics. *Scopolamine* - Scopolamine has a shorter duration of action compared to atropine and is less commonly used as the first-line agent for **breaking synechiae** in severe inflammation. - While it is a **cycloplegic agent**, it is often reserved for patients who have sensitivity to atropine or require a shorter-acting therapeutic agent. *Miotics* - Miotics, such as **pilocarpine**, cause **pupil constriction** (miosis) by contracting the sphincter pupillae. - These are contraindicated in the treatment of synechiae because they would worsen existing **posterior synechiae** and increase the risk of **pupillary block**.

Q: What is the duration of cycloplegia induced by atropine in an adult?

7-10 days. ### Explanation **Correct Answer: C. 7-10 days** **Mechanism and Rationale:** Atropine is a potent, non-selective muscarinic antagonist. In the eye, it blocks the M3 receptors on the **ciliary muscle** (causing cycloplegia or paralysis of accommodation) and the **sphincter pupillae** (causing mydriasis). Atropine has the strongest binding affinity among all clinical cycloplegics. While its peak effect occurs within hours, its duration of action is prolonged due to its slow dissociation from the receptors and its sequestration in the uveal pigment (melanin). In an adult, the cycloplegic effect typically lasts **7 to 10 days**, while the mydriatic effect can persist for up to 14 days. **Analysis of Incorrect Options:** * **Option A (6 hours):** This is the approximate duration of action for **Tropicamide**, the shortest-acting mydriatic/cycloplegic, making it ideal for routine fundus examinations. * **Option B (2-3 days):** This corresponds to the duration of action for **Homatropine**. It is often used in the treatment of anterior uveitis to prevent synechiae without the prolonged blurriness of atropine. * **Option D (1-2 days):** This is the typical duration for **Cyclopentolate**, which is the drug of choice for cycloplegic refraction in children due to its rapid onset and moderate duration. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Atropine is the drug of choice for refraction in children **under 7 years** of age (especially those with accommodative esotropia) because their ciliary muscle tone is too high for weaker agents. * **Formulation:** In children, **1% Atropine ointment** is preferred over drops to minimize systemic absorption through the nasolacrimal duct, reducing the risk of systemic toxicity (fever, flushing, tachycardia). * **Contraindication:** All mydriatics/cycloplegics are strictly contraindicated in patients with **Primary Angle Closure Glaucoma (PACG)** as they can precipitate an acute attack.

Q: Which antiglaucoma drug is contraindicated in acute uveitis?

Pilocarpine. **Explanation:** The correct answer is **Pilocarpine**. In acute uveitis, the primary goal of treatment is to rest the ciliary body and prevent the formation of **posterior synechiae** (adhesions between the iris and the lens). * **Pilocarpine** is a miotic (parasympathomimetic). It causes pupillary constriction and ciliary muscle contraction. In an inflamed eye, miosis increases the surface area of contact between the iris and the lens, significantly increasing the risk of **posterior synechiae**. Furthermore, it breaks the blood-aqueous barrier, potentially worsening the intraocular inflammation. Therefore, it is strictly contraindicated. **Analysis of Other Options:** * **Timolol (Beta-blocker):** It reduces aqueous humor production and does not affect pupil size or the blood-aqueous barrier, making it a safe first-line choice for secondary glaucoma in uveitis. * **Brimonidine (Alpha-2 agonist):** It reduces aqueous production and increases uveoscleral outflow. It is generally safe, though it may occasionally cause granulomatous uveitis as a side effect. * **Latanoprost (Prostaglandin Analog):** While some clinicians avoid PGAs in active uveitis due to a theoretical risk of exacerbating inflammation or causing cystoid macular edema (CME), they are **not** as strictly contraindicated as Pilocarpine. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Uveitis:** Atropine (a strong cycloplegic) is used to "put the eye to rest" and prevent synechiae. * **Avoid in Uveitic Glaucoma:** Pilocarpine (due to synechiae) and Carbonic Anhydrase Inhibitors (relative contraindication if there is corneal endothelial compromise). * **Inverse Relationship:** Miotics (Pilocarpine) worsen uveitis; Mydriatics/Cycloplegics (Atropine) treat uveitis.

Q: What is the drug of choice for Herpes simplex Endophthalmitis?

Acyclovir. **Explanation:** **Acyclovir** is the drug of choice for Herpes Simplex Virus (HSV) infections of the eye, including endophthalmitis and keratitis. Its mechanism of action involves selective inhibition of viral DNA polymerase. It acts as a prodrug that requires phosphorylation by viral **thymidine kinase** to become active (Acyclovir triphosphate), ensuring high selectivity for infected cells and a superior safety profile compared to older antivirals. **Analysis of Options:** * **B. Vidarabine:** An older antiviral that was used for HSV keratitis. However, it is significantly more toxic to the corneal epithelium and less effective than Acyclovir. It is now largely obsolete in clinical practice. * **C. Amantadine:** This is an anti-influenza agent (specifically Influenza A) and is also used in Parkinson’s disease. It has no clinical efficacy against the Herpesviridae family. * **D. Interferon:** While interferons have antiviral properties and can be used as adjuvant therapy in resistant cases of dendritic ulcers, they are not the primary drug of choice for acute HSV endophthalmitis due to inconsistent results and side effects. **High-Yield Clinical Pearls for NEET-PG:** * **HSV Keratitis:** Characterized by **dendritic ulcers** with terminal bulbs. These stain with Rose Bengal (dead cells at the margin) and Fluorescein (the ulcer base). * **Steroid Contraindication:** Topical steroids are strictly contraindicated in the presence of an active epithelial dendritic ulcer as they can lead to **Geographic ulcers**. * **DOC for CMV Retinitis:** Ganciclovir (Valganciclovir is the oral DOC). * **DOC for HZO (Herpes Zoster Ophthalmicus):** Oral Acyclovir (800mg 5x daily), started within 72 hours of rash onset.

Q: What agent is used for pupil dilatation in children?

Atropine. **Explanation:** In pediatric ophthalmology, the drug of choice for pupil dilatation and cycloplegic refraction is **Atropine**. **1. Why Atropine is Correct:** Children have very high accommodative power due to a strong ciliary muscle. To perform an accurate refraction (especially to detect latent hypermetropia or accommodative esotropia), complete paralysis of the ciliary muscle (**cycloplegia**) is required. Atropine is the most potent cycloplegic available. It is typically administered as a 1% ointment or drops for 3 days prior to the examination to ensure maximal effect. **2. Why the other options are incorrect:** * **Homatropine:** It is a semi-synthetic derivative of atropine but is significantly less potent. It is rarely used for refraction in children because it may result in incomplete cycloplegia. * **Tropicamide:** While it has the fastest onset and shortest duration (making it the drug of choice for adults), its cycloplegic action is too weak for the strong accommodative reflex of a child. * **Phenylephrine:** This is a sympathomimetic (alpha-1 agonist) that causes mydriasis (dilation) but **no cycloplegia**. It is often used as an adjunct but cannot be used alone for pediatric refraction. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** Atropine is the DOC for children <7 years; Cyclopentolate is preferred for children 7–12 years; Tropicamide is preferred for adults. * **Systemic Toxicity:** In children, always apply pressure over the lacrimal sac (punctal occlusion) after instilling drops to prevent systemic absorption, which can cause "Atropine flushing," fever, and tachycardia. * **Contraindication:** Avoid atropine in children with Down Syndrome, as they may show an exaggerated pupillary response and heart rate.

Question 1

A patient came with redness and pain, and you dilated the pupil to break the synechiae. Which drug was used, looking at this picture?

Accepted Answer

Atropine

Answer

Phenylephrine

Answer

Scopolamine

Answer

Miotics

Question 2

What is the duration of cycloplegia induced by atropine in an adult?

Accepted Answer

7-10 days

Answer

6 hours

Answer

2-3 days

Answer

1-2 days

Question 3

Which antiglaucoma drug is contraindicated in acute uveitis?

Accepted Answer

Pilocarpine

Answer

Timolol

Answer

Brimonidine

Answer

Latanoprost

Question 4

What is the drug of choice for Herpes simplex Endophthalmitis?

Accepted Answer

Acyclovir

Answer

Vidarabine

Answer

Amantidine

Answer

Interferon

Question 5

What agent is used for pupil dilatation in children?

Accepted Answer

Atropine

Answer

Homatropine

Answer

Tropicamide

Answer

Phenylephrine

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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