Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology Indian Medical PG Practice Questions and MCQs

Question 81: Which of the following antivirals cannot be used topically in the eye?

A. Acyclovir
B. Ganciclovir
C. Idoxuridine
D. Famciclovir (Correct Answer)

Explanation: **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).

Question 82: All the following drugs are known to cause anterior uveitis except?

A. Rifabutin
B. Cidofovir
C. Metipranolol
D. Gatifloxacin (Correct Answer)

Explanation: **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**.

Question 83: All of the following drugs are associated with corneal deposition except?

A. Chloroquine
B. Amiodarone
C. Quinacrine
D. Antimony (Correct Answer)

Explanation: **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).

Question 84: Intraocular tension is decreased by all except?

A. Pilocarpine
B. Atropine (Correct Answer)
C. Apraclonidine
D. Tropicamide

Explanation: **Explanation:** The regulation of intraocular pressure (IOP) depends on the balance between aqueous humor production and its drainage. **Why Atropine is the Correct Answer:** Atropine is a potent **parasympatholytic (antimuscarinic)** agent. It causes **mydriasis** (dilation of the pupil) and **cycloplegia** (paralysis of the ciliary muscle). In eyes with narrow anterior chamber angles, mydriasis causes the peripheral iris to bunch up, potentially obstructing the trabecular meshwork. Furthermore, by relaxing the ciliary muscle, it decreases the tension on the scleral spur, which reduces the efficiency of aqueous outflow through the trabecular route. Therefore, Atropine **increases** IOP and is strictly contraindicated in primary angle-closure glaucoma. **Analysis of Other Options:** * **A. Pilocarpine:** A direct-acting miotic (parasympathomimetic). It contracts the ciliary muscle, pulling the scleral spur and opening the trabecular meshwork, thereby **decreasing** IOP by increasing aqueous outflow. * **C. Apraclonidine:** An alpha-2 adrenergic agonist. It **decreases** IOP by reducing the rate of aqueous humor production and enhancing uveoscleral outflow. * **D. Tropicamide:** While Tropicamide is a mydriatic/cycloplegic like Atropine, it is often used in clinical practice for fundus examination. However, in the context of this specific question format (often seen in older NEET-PG/AIIMS patterns), Atropine is the "most" correct answer as it is the prototypical drug that causes a significant and prolonged rise in IOP. *Note: Technically, both B and D can increase IOP, but Atropine is the classic pharmacological example.* **High-Yield Clinical Pearls for NEET-PG:** * **Drug of choice for Acute Angle Closure Glaucoma:** IV Acetazolamide (to rapidly lower IOP) and Pilocarpine (once IOP is <30 mmHg). * **Prostaglandin Analogs (e.g., Latanoprost):** Currently the first-line medical therapy for Open Angle Glaucoma; they work by increasing **uveoscleral outflow**. * **Beta-blockers (e.g., Timolol):** Decrease IOP by reducing aqueous **production** from the ciliary body.

Question 85: Brinzolamide is:

A. A competitive and reversible carbonic anhydrase inhibitor
B. A non-competitive and reversible carbonic anhydrase inhibitor (Correct Answer)
C. A competitive and irreversible carbonic anhydrase inhibitor
D. A non-competitive and irreversible carbonic anhydrase inhibitor

Explanation: **Explanation:** **Brinzolamide** is a highly specific, topical **carbonic anhydrase inhibitor (CAI)** used primarily to reduce intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension [1]. 1. **Why Option B is Correct:** Carbonic anhydrase inhibitors like Brinzolamide and Dorzolamide work by binding to the **Carbonic Anhydrase II (CA-II)** isoenzyme in the ciliary processes. The mechanism is **non-competitive**, meaning the drug binds to a site other than the active site (or binds regardless of substrate concentration), and **reversible**, meaning the drug-enzyme complex can dissociate over time. By inhibiting this enzyme, it decreases the production of bicarbonate ions, which subsequently reduces aqueous humor secretion by approximately 40-50%. 2. **Why Other Options are Incorrect:** * **Options A & C (Competitive):** Brinzolamide does not compete directly with the natural substrate ($CO_2$ and $H_2O$) for the active site of the enzyme. * **Options C & D (Irreversible):** Irreversible inhibition would lead to permanent enzyme inactivation, which is not the case here. The effect of Brinzolamide wears off as the drug is cleared from the ocular tissues, confirming its reversible nature. **High-Yield Clinical Pearls for NEET-PG:** * **Formulation:** Brinzolamide is a 1% ophthalmic **suspension**. Unlike Dorzolamide (a solution), Brinzolamide has a physiological pH, making it **less irritating** and causing less stinging/burning upon instillation. * **Side Effects:** The most common side effect is **blurred vision** (due to the suspension formulation) and a **bitter taste** (dysgeusia) following nasolacrimal drainage. * **Contraindications:** Avoid in patients with known **sulfonamide allergies**, as CAIs are sulfonamide derivatives. * **Comparison:** While Acetazolamide is the systemic prototype, Brinzolamide and Dorzolamide are the preferred topical agents to avoid systemic side effects like metabolic acidosis and hypokalemia.

Question 86: What is the drug of choice for corneal herpes?

A. Idoxuridine
B. Acyclovir (Correct Answer)
C. Vidarabine
D. Amantadine

Explanation: **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."

Question 87: 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?

A. Atropine
B. Antazoline (Correct Answer)
C. Pilocarpine
D. Phenylephrine

Explanation: ### **Explanation** **Diagnosis: Seasonal Allergic Conjunctivitis (SAC)** The clinical presentation—a young patient with recurrent, seasonal episodes of conjunctivitis occurring in early summer—is classic for **Seasonal Allergic Conjunctivitis**. This is a Type I hypersensitivity reaction triggered by airborne allergens (like pollen). **1. Why Antazoline is Correct:** **Antazoline** is a first-generation **antihistamine** (H1-receptor antagonist). Since the underlying pathophysiology of allergic conjunctivitis involves the release of histamine from mast cells, antihistamines are the primary pharmacological intervention to relieve symptoms like itching, redness, and lacrimation. It is often used in combination with naphazoline (a vasoconstrictor) for symptomatic relief. **2. Why Other Options are Incorrect:** * **A. Atropine:** A potent long-acting mydriatic and cycloplegic. It is used in uveitis to prevent synechiae or for refraction in children, but it has no role in treating allergy and would cause blurred vision and photophobia. * **C. Pilocarpine:** A miotic (parasympathomimetic) used primarily in the management of glaucoma to lower intraocular pressure. It would worsen symptoms by causing miosis and ciliary spasm. * **D. Phenylephrine:** An alpha-1 agonist used as a decongestant and mydriatic. While it may temporarily reduce redness (vasoconstriction), it does not treat the allergic mechanism and can cause "rebound hyperemia" upon discontinuation. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice (Prophylaxis):** Mast cell stabilizers (e.g., **Sodium Cromoglicate**) are preferred for preventing episodes if started before the season begins. * **Drug of Choice (Acute relief):** Dual-action agents (Antihistamine + Mast cell stabilizer) like **Olopatadine** or **Ketotifen** are currently considered the gold standard. * **Vernal Keratoconjunctivitis (VKC):** If the question mentioned "Cobblestone papillae" or "Horner-Trantas dots," think of VKC, a more severe bilateral seasonal allergy common in young boys.

Question 88: Which of the following local anesthetic agents is the drug of choice for removal of corneal foreign bodies?

A. Benzocaine
B. Lignocaine
C. Tetracaine (Correct Answer)
D. Prilocaine

Explanation: **Explanation:** **Tetracaine (Amethocaine)** is the drug of choice for topical anesthesia in minor ophthalmic procedures, such as the removal of corneal foreign bodies, tonometry, and gonioscopy. **Why Tetracaine is correct:** Tetracaine is an ester-type local anesthetic known for its **rapid onset (approx. 30 seconds)** and **potent surface anesthesia**. It provides a deeper level of corneal anesthesia compared to other agents, making it ideal for procedures involving corneal manipulation. While it can cause a transient stinging sensation upon instillation, its efficacy in numbing the corneal nerves is superior for short-duration clinical tasks. **Why the other options are incorrect:** * **Benzocaine:** Primarily used for mucosal anesthesia (e.g., sore throat lozenges or dental gels). It is poorly soluble in water and is not used topically in the eye due to its formulation and lower potency for corneal nerves. * **Lignocaine (Lidocaine):** While widely used for infiltration (subconjunctival or peribulbar blocks), it is less commonly used as a first-line *topical* drop for foreign body removal because it is more irritating to the corneal epithelium than tetracaine or proparacaine. * **Prilocaine:** Mainly used for infiltration or intravenous regional anesthesia. It is not a standard topical ophthalmic anesthetic and carries a risk of methemoglobinemia if used in high systemic doses. **High-Yield Clinical Pearls for NEET-PG:** * **Proparacaine:** Another common topical anesthetic; it is often preferred in clinical practice over tetracaine because it causes **less stinging**, though tetracaine remains the classic textbook "drug of choice" for potency. * **Warning:** Topical anesthetics should **never** be prescribed for home use or chronic pain relief, as they are **epitheliotoxic** and can lead to "anesthetic-induced keratopathy" and delayed wound healing. * **Mechanism:** All local anesthetics work by blocking **voltage-gated sodium channels**, preventing nerve impulse conduction.

Question 89: Which of the following cycloplegic agents is considered the strongest?

A. Atropine (Correct Answer)
B. Homatropine
C. Cyclopentolate
D. Tropicamide

Explanation: **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**.

Question 90: Which drug is contraindicated in an asthmatic female for the treatment of glaucoma?

A. Prostaglandin
B. Timolol (Correct Answer)
C. Apraclanidine
D. Bromonidine

Explanation: **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.

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Ocular Pharmacokinetics

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Anti-infective Agents

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Anti-inflammatory Drugs

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Antiglaucoma Medications

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Mydriatics and Cycloplegics

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Ocular Lubricants

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Anti-VEGF Agents

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Ocular Diagnostic Agents

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Anesthetics in Ophthalmology

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Preservatives and Their Effects

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Ocular Toxicology

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Novel Drug Delivery Systems

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