Ophthalmic Pharmacology Practice Questions

Q: Which of the following antivirals cannot be used topically in the eye?

Famciclovir. **Explanation:** The correct answer is **Famciclovir**. **1. Why Famciclovir is the correct answer:** Famciclovir is a **prodrug** of penciclovir. It is designed specifically for high oral bioavailability and requires systemic absorption to be converted into its active form by first-pass metabolism in the liver and intestinal wall. Consequently, it is **only available in oral formulations** and cannot be used topically in the eye. In ophthalmic practice, it is primarily used orally for the treatment of Herpes Zoster Ophthalmicus (HZO) and recurrent Herpes Simplex Keratitis. **2. Analysis of Incorrect Options:** * **Acyclovir:** Available as a **3% ophthalmic ointment**. It is a gold standard topical treatment for Herpes Simplex Keratitis (dendritic ulcers) due to its selective toxicity and good corneal penetration. * **Ganciclovir:** Available as a **0.15% ophthalmic gel**. It is highly effective for epithelial keratitis and is often preferred over acyclovir ointment because it is less toxic to the corneal epithelium. * **Idoxuridine:** This was the **first antiviral** developed for topical use (0.1% drops/0.5% ointment). However, it is rarely used today due to significant ocular toxicity and the availability of superior alternatives like Ganciclovir. **3. Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** For Herpes Simplex Epithelial Keratitis, topical **Ganciclovir (0.15% gel)** or **Acyclovir (3% ointment)** are preferred. * **Trifluridine:** Another topical antiviral (1% drops); it is more potent than Idoxuridine but can cause "toxic follicular conjunctivitis." * **Contraindication:** Topical steroids are strictly contraindicated in active dendritic (epithelial) ulcers as they can lead to **"Geographic ulcers."** * **Systemic use:** Oral Famciclovir or Valacyclovir are preferred over oral Acyclovir for Herpes Zoster due to better dosing schedules (TID vs. 5 times/day).

Q: All the following drugs are known to cause anterior uveitis except?

Gatifloxacin. **Explanation:** Drug-induced uveitis is a critical topic in ophthalmic pharmacology. The correct answer is **Gatifloxacin**, as it is not typically associated with anterior uveitis. **1. Why Gatifloxacin is the Correct Answer:** Gatifloxacin is a fourth-generation fluoroquinolone used topically to treat bacterial conjunctivitis and keratitis. While it can cause local irritation or punctate keratitis, it is **not** a recognized cause of anterior uveitis. In contrast, systemic fluoroquinolones (like Moxifloxacin) have been linked to **Bilateral Acute Iris Transillumination (BAIT)**, but Gatifloxacin is generally excluded from the list of classic uveitis-inducing agents. **2. Analysis of Incorrect Options:** * **Rifabutin (Option A):** A potent anti-mycobacterial drug used in HIV patients for MAC prophylaxis. It is a well-known cause of severe, often bilateral, acute anterior uveitis with hypopyon. * **Cidofovir (Option B):** An antiviral used for CMV retinitis. It frequently causes anterior uveitis and hypotony (low IOP) due to its toxic effect on the ciliary body epithelium. * **Metipranolol (Option C):** A non-selective beta-blocker used for glaucoma. It has been specifically linked to granulomatous or non-granulomatous anterior uveitis, a side effect rarely seen with other beta-blockers like Timolol. **Clinical Pearls for NEET-PG:** * **Mnemonic for Uveitis-inducing drugs:** "**S**ubstances **C**ause **R**eal **I**nflammation" (**S**ulfonamides, **C**idofovir, **R**ifabutin, **I**ndinavir/Ibis). * **Bisphosphonates (Zoledronate):** Another high-yield cause of drug-induced uveitis and scleritis. * **Brimonidine:** Can cause a delayed-type hypersensitivity reaction manifesting as granulomatous uveitis. * **Hypopyon Uveitis:** Classically associated with **Rifabutin** and **Behçet’s disease**.

Q: All of the following drugs are associated with corneal deposition except?

Antimony. **Explanation:** The correct answer is **Antimony**. This question tests your knowledge of systemic drugs that cause ocular toxicity, specifically **Corneal Verticillata (Vortex Keratopathy)**. **1. Why Antimony is the correct answer:** Antimony is a heavy metal used primarily in the treatment of Leishmaniasis. While it can have systemic side effects, it is **not** associated with corneal deposits. In contrast, heavy metals that *do* cause corneal deposits include Gold (Chrysiasis), Silver (Argyrosis), and Copper (Kayser-Fleischer ring). **2. Analysis of Incorrect Options:** * **Chloroquine:** A classic cause of **Corneal Verticillata**. It deposits in the basal corneal epithelium in a whorl-like pattern. While these deposits are usually asymptomatic and reversible, they serve as a marker for potential retinal toxicity (Bull’s eye maculopathy). * **Amiodarone:** This anti-arrhythmic drug is the **most common cause** of Corneal Verticillata. Deposits occur in nearly 100% of patients on long-term therapy (>400mg/day). They rarely affect vision but can cause "blue-green halos." * **Quinacrine:** An antimalarial and antiprotozoal drug that, like chloroquine, is well-documented to cause yellowish-brown whorl-like corneal epithelial deposits. **3. NEET-PG High-Yield Pearls:** * **Mnemonic for Corneal Verticillata (CHAI-T):** **C**hloroquine, **H**ydroxychloroquine, **A**miodarone, **I**ndomethacin, and **T**amoxifen. * **Fabry’s Disease:** The most important systemic disease associated with Corneal Verticillata (due to glycosphingolipid deposition). * **Gold Deposits:** Occur in the deep stroma (Chrysiasis). * **Iron Deposits:** Usually occur in the epithelium (e.g., Hudson-Stahli line, Fleischer ring in Keratoconus).

Q: What is the drug of choice for corneal herpes?

Acyclovir. **Explanation:** **Acyclovir** is the drug of choice for corneal herpes (Herpetic Keratitis) due to its high efficacy and superior safety profile. It is a selective inhibitor of viral DNA polymerase. Its mechanism involves phosphorylation by viral **thymidine kinase** into acyclovir monophosphate, which is then converted by host cell kinases into the active triphosphate form. This ensures the drug primarily targets virus-infected cells, resulting in minimal toxicity to the healthy corneal epithelium. **Analysis of Options:** * **Idoxuridine (Option A):** This was the first antiviral used for herpes, but it is no longer the drug of choice. It is non-selective, leading to significant ocular surface toxicity (follicular conjunctivitis, punctate epithelial erosions). * **Vidarabine (Option B):** While effective against HSV, it has poor solubility and higher toxicity compared to Acyclovir. It is generally reserved for cases resistant to Acyclovir. * **Amantadine (Option D):** This is an anti-influenza medication (M2 ion channel inhibitor) and has no clinical role in treating herpes simplex virus infections. **High-Yield Clinical Pearls for NEET-PG:** * **Topical Formulation:** 3% Acyclovir eye ointment is typically used 5 times a day. * **Ganciclovir 0.15% gel** is an alternative first-line agent with even lower toxicity and better patient compliance. * **Trifluorothymidine (Trifluridine):** Often considered the most potent topical antiviral for epithelial keratitis but is more toxic than Acyclovir. * **Contraindication:** Never use **topical steroids** in active dendritic (epithelial) keratitis, as they can lead to the formation of a "Geographic Ulcer."

Q: Which of the following cycloplegic agents is considered the strongest?

Atropine. **Explanation:** **1. Why Atropine is Correct:** Atropine is the **strongest and longest-acting** cycloplegic and mydriatic agent available. It is a non-selective muscarinic antagonist that produces profound paralysis of the ciliary muscle (cycloplegia) and the sphincter pupillae (mydriasis). Its maximal cycloplegic effect is reached in 1–3 hours, but the recovery can take up to **7–12 days**. Due to its high potency, it is the gold standard for cycloplegic refraction in children under 5 years of age (especially those with accommodative esotropia), as their ciliary muscle tone is too strong for weaker agents. **2. Why the Other Options are Incorrect:** * **Homatropine (B):** It is about 1/10th as potent as Atropine. It has a shorter duration of action (1–3 days) and is primarily used in treating anterior uveitis to prevent synechiae rather than for refraction. * **Cyclopentolate (C):** While it has a rapid onset (30–60 mins), its potency is less than Atropine. It is the drug of choice for cycloplegic refraction in children aged 5–15 years. * **Tropicamide (D):** It is the **weakest** and shortest-acting agent (duration 4–6 hours). It is the drug of choice for routine fundus examination (mydriasis) but is a poor cycloplegic. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Refraction):** * <5 years: Atropine (Ointment is preferred over drops to prevent systemic toxicity via nasolacrimal duct). * 5–15 years: Cyclopentolate. * Adults: Homatropine or Tropicamide. * **Antidote:** Physostigmine is used for Atropine poisoning. * **Contraindication:** All cycloplegics are contraindicated in patients with a predisposition to **Angle-Closure Glaucoma**.

Q: Which drug is contraindicated in an asthmatic female for the treatment of glaucoma?

Timolol. **Explanation:** The correct answer is **Timolol** because it is a non-selective beta-blocker. **1. Why Timolol is the correct answer:** Timolol works by blocking $\beta_1$ and $\beta_2$ receptors. While $\beta_1$ blockade reduces aqueous humor production in the ciliary body (treating glaucoma), $\beta_2$ blockade causes **bronchoconstriction** in the lungs. In patients with asthma or COPD, this can trigger a life-threatening bronchospasm. Even when administered topically as eye drops, significant systemic absorption occurs via the nasolacrimal duct, bypassing first-pass metabolism. **2. Why the other options are incorrect:** * **Prostaglandins (e.g., Latanoprost):** These are the first-line treatment for glaucoma. They work by increasing uveoscleral outflow and have no significant effect on bronchial smooth muscle. * **Apraclonidine & Brimonidine:** These are $\alpha_2$-adrenergic agonists. They reduce aqueous production and increase outflow. Their primary side effects are local (allergic conjunctivitis) or systemic (lethargy, dry mouth), but they do not cause bronchospasm. **Clinical Pearls for NEET-PG:** * **Betaxolol** is a **cardioselective ($\beta_1$) blocker** and is the preferred beta-blocker if one must be used in a patient with mild respiratory issues, though it is still used with caution. * To minimize systemic absorption of ocular drugs, advise patients to perform **punctal occlusion** (pressing the inner corner of the eye) for 2–3 minutes after instillation. * **Absolute Contraindications for Timolol:** Bronchial asthma, severe COPD, bradycardia, and second or third-degree heart block.

Question 1

Which of the following antivirals cannot be used topically in the eye?

Accepted Answer

Famciclovir

Answer

Acyclovir

Answer

Ganciclovir

Answer

Idoxuridine

Question 2

All the following drugs are known to cause anterior uveitis except?

Accepted Answer

Gatifloxacin

Answer

Rifabutin

Answer

Cidofovir

Answer

Metipranolol

Question 3

All of the following drugs are associated with corneal deposition except?

Accepted Answer

Antimony

Answer

Chloroquine

Answer

Amiodarone

Answer

Quinacrine

Question 4

Intraocular tension is decreased by all except?

Accepted Answer

Atropine

Answer

Pilocarpine

Answer

Apraclonidine

Answer

Tropicamide

Question 5

Brinzolamide is:

Accepted Answer

A non-competitive and reversible carbonic anhydrase inhibitor

Answer

A competitive and reversible carbonic anhydrase inhibitor

Answer

A competitive and irreversible carbonic anhydrase inhibitor

Answer

A non-competitive and irreversible carbonic anhydrase inhibitor

Question 6

What is the drug of choice for corneal herpes?

Accepted Answer

Acyclovir

Answer

Idoxuridine

Answer

Vidarabine

Answer

Amantadine

Question 7

A 19-year-old woman presents with recurrent conjunctivitis occurring annually in early summer and lasting for approximately six weeks. Which of the following is the most appropriate drug for this condition?

Accepted Answer

Antazoline

Answer

Atropine

Answer

Pilocarpine

Answer

Phenylephrine

Question 8

Which of the following local anesthetic agents is the drug of choice for removal of corneal foreign bodies?

Accepted Answer

Tetracaine

Answer

Benzocaine

Answer

Lignocaine

Answer

Prilocaine

Question 9

Which of the following cycloplegic agents is considered the strongest?

Accepted Answer

Atropine

Answer

Homatropine

Answer

Cyclopentolate

Answer

Tropicamide

Question 10

Which drug is contraindicated in an asthmatic female for the treatment of glaucoma?

Accepted Answer

Timolol

Answer

Prostaglandin

Answer

Apraclanidine

Answer

Bromonidine

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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