Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology Indian Medical PG Practice Questions and MCQs

Question 11: Which of the following medications can cause acquired nasolacrimal duct obstruction?

A. Timolol
B. Pilocarpine (Correct Answer)
C. Brimonidine
D. Dorzolamide

Explanation: **Explanation:** **Pilocarpine** is a parasympathomimetic (miotic) agent that has been historically associated with **acquired nasolacrimal duct obstruction (NLDO)** and canalicular stenosis. The underlying mechanism involves the drug’s ability to induce chronic inflammation and subepithelial fibrosis of the mucosal lining of the lacrimal drainage system. Long-term topical use leads to cicatricial (scarring) changes, effectively narrowing or completely occluding the puncta and canaliculi. **Analysis of Options:** * **Pilocarpine (Correct):** It is the most notorious glaucoma medication for causing punctal and canalicular stenosis. Other drugs associated with this side effect include **Idoxuridine**, **Phospholine iodide**, and systemic chemotherapeutic agents like **5-Fluorouracil (5-FU)** and **Docetaxel**. * **Timolol (Incorrect):** A non-selective beta-blocker. While it can cause dry eye symptoms and corneal anesthesia, it is not typically associated with cicatricial NLDO. * **Brimonidine (Incorrect):** An alpha-2 agonist. Its most common side effect is a **follicular conjunctivitis** (allergic reaction) in up to 30% of patients. * **Dorzolamide (Incorrect):** A topical carbonic anhydrase inhibitor. Common side effects include a bitter taste (dysgeusia) and stinging, but not ductal obstruction. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of NLDO in adults:** Chronic dacryocystitis/Involutional stenosis. * **Drug-induced canalicular stenosis:** Always remember **5-FU** and **Pilocarpine**. * **Pilocarpine Side Effects:** Miosis (leading to night blindness), brow ache (due to ciliary muscle contraction), and retinal detachment (due to peripheral retinal traction). * **Management:** If stenosis occurs, the drug must be discontinued immediately; advanced cases may require **Dacryocystorhinostomy (DCR)** or silicone intubation.

Question 12: What is the drug of choice for the treatment of trachoma?

A. Tetracycline eye ointment (Correct Answer)
B. Ciprofloxacin eye ointment
C. Doxycycline eye ointment
D. None of the above

Explanation: **Explanation:** Trachoma, caused by *Chlamydia trachomatis* (serotypes A, B, Ba, and C), is a leading cause of preventable blindness worldwide. The management follows the WHO-recommended **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement). **1. Why Tetracycline is the Correct Answer:** According to the WHO guidelines for the mass treatment of trachoma, **1% Tetracycline eye ointment** applied twice daily for 6 weeks is the traditional drug of choice for topical therapy. It inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. While oral Azithromycin (single dose) is now the preferred systemic treatment for mass drug administration (MDA), topical Tetracycline remains the standard topical agent, especially in areas where systemic drugs are contraindicated (e.g., pregnancy or infants under 6 months). **2. Why the Other Options are Incorrect:** * **Ciprofloxacin (B):** While a potent fluoroquinolone, it is not the first-line treatment for Chlamydial infections; it is primarily used for bacterial keratitis and conjunctivitis caused by common pyogenic organisms. * **Doxycycline (C):** While oral Doxycycline is effective against Chlamydia, it is not typically used as an **eye ointment** for trachoma. Systemic Doxycycline is an alternative to Azithromycin but is contraindicated in children and pregnant women. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Systemic):** Oral Azithromycin (20 mg/kg up to 1g) as a single dose. * **SAFE Strategy:** **S**urgery (for trichiasis), **A**ntibiotics (Azithromycin/Tetracycline), **F**acial cleanliness, **E**nvironmental change. * **Pathognomonic Signs:** Herbert’s pits (limbal follicles) and Arlt’s line (conjunctival scarring). * **Vector:** The common housefly (*Musca sorbens*).

Question 13: Which of the following drugs is an alpha 2 agonist?

A. Apraclonidine (Correct Answer)
B. Timolol
C. Prostaglandin analogues
D. Prostaglandin analogues

Explanation: **Explanation:** **Apraclonidine** is the correct answer because it is a selective **alpha-2 (α2) adrenergic agonist**. In ophthalmology, α2 agonists (including Apraclonidine and Brimonidine) lower intraocular pressure (IOP) by a dual mechanism: they decrease the production of aqueous humor from the ciliary body and, to a lesser extent, increase uveoscleral outflow. **Analysis of Incorrect Options:** * **Timolol:** This is a **non-selective beta-blocker** (β1 and β2). It is a first-line agent for glaucoma that works primarily by reducing aqueous humor production. * **Prostaglandin Analogues (e.g., Latanoprost):** These are the most potent first-line drugs for glaucoma. They work by **increasing uveoscleral outflow** (the unconventional pathway) rather than acting on alpha receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Apraclonidine** is primarily used to prevent or treat acute IOP spikes following anterior segment laser procedures (like Nd:YAG laser capsulotomy or iridotomy). * **Brimonidine** is more selective for α2 receptors than Apraclonidine and is used for long-term glaucoma management. A common side effect is follicular conjunctivitis. * **Contraindication:** Alpha-2 agonists are strictly contraindicated in infants and young children (under 2 years) as they can cross the blood-brain barrier and cause CNS depression, apnea, and bradycardia. * **Mnemonic for Aqueous Suppressants:** "ABC" – **A**lpha-2 agonists, **B**eta-blockers, and **C**arbonic anhydrase inhibitors.

Question 14: Which of the following antiglaucoma drugs can result in hypertrichosis?

A. Apraclonidine
B. Latanoprost (Correct Answer)
C. Pilocarpine
D. Dipivefrine

Explanation: **Explanation:** **Latanoprost** is a Prostaglandin F2α (PGF2α) analogue, which is the first-line treatment for Open-Angle Glaucoma. It works by increasing the **uveoscleral outflow** of aqueous humor. A well-known side effect of prostaglandin analogues is **hypertrichosis** (increased growth, thickness, and pigmentation of eyelashes). This occurs because prostaglandins prolong the **anagen (growth) phase** of the hair follicle cycle. **Analysis of Incorrect Options:** * **Apraclonidine:** An alpha-2 adrenergic agonist that decreases aqueous production. Common side effects include lid retraction and conjunctival blanching, but not hair growth. * **Pilocarpine:** A direct-acting miotic (parasympathomimetic) that increases trabecular outflow. Side effects include miosis, brow ache, and retinal detachment; it has no effect on hair follicles. * **Dipivefrine:** A prodrug of epinephrine (sympathomimetic). It can cause localized allergic reactions and adrenochrome deposits in the conjunctiva, but not hypertrichosis. **High-Yield Clinical Pearls for NEET-PG:** 1. **Prostaglandin Side Effects:** Remember the triad of **Triple P**: **P**eriorbital pigmentation, **P**upillary iris darkening (permanent), and **P**roliferation of lashes (hypertrichosis). 2. **Cystoid Macular Edema (CME):** Latanoprost is contraindicated in aphakic or pseudophakic patients with a torn posterior capsule due to the risk of CME. 3. **Bimatoprost:** Another prostaglandin analogue used specifically for the treatment of hypotrichosis of the eyelashes (commercially available as Latisse). 4. **Uveitis:** Prostaglandins should be avoided in inflammatory glaucoma as they may exacerbate intraocular inflammation.

Question 15: Role of atropine in iridocyclitis includes all of the following except:

A. It dilates the pupil, prevents the formation of synechiae and may break the already formed synechiae
B. Gives comfort and rest to the eye by relieving ciliary muscle spasm
C. It reduces exudation by decreasing hyperemia
D. It lowers the intraocular pressure by increasing aqueous outflow facility (Correct Answer)

Explanation: **Explanation:** Atropine, a potent parasympatholytic (anticholinergic) agent, is the drug of choice in the management of acute iridocyclitis. However, it **does not lower intraocular pressure (IOP)**; in fact, by causing mydriasis, it can potentially increase IOP in eyes with narrow angles by crowding the angle of the anterior chamber. **Why Option D is the correct answer:** Atropine causes paralysis of the ciliary muscle and the sphincter pupillae. It has no mechanism to increase aqueous outflow. In the context of iridocyclitis, any reduction in IOP seen after atropine use is usually secondary to the resolution of inflammation, not a direct pharmacological effect on outflow facility. **Analysis of other options:** * **Option A:** By inducing strong mydriasis, atropine keeps the pupil moving and dilated, which prevents the formation of **posterior synechiae** (adhesion of iris to lens) and can break freshly formed ones. * **Option B:** It acts as a **cycloplegic**, paralyzing the ciliary muscle. This relieves the painful ciliary spasms associated with inflammation, providing significant symptomatic relief ("ciliary rest"). * **Option C:** Atropine acts as a mild vasoconstrictor in the ocular tissues, which **decreases hyperemia** and capillary permeability, thereby reducing the inflammatory exudation into the anterior chamber. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Atropine (1%) ointment or drops is the DOC for acute iridocyclitis. * **Duration:** Atropine is the longest-acting cycloplegic (effect lasts 7–10 days). * **Contraindication:** Avoid in patients with primary angle-closure glaucoma. * **Phenylephrine Synergism:** Often used with atropine to maximize pupillary dilation to break stubborn synechiae (Mydricaine subconjunctival injection).

Question 16: Which of the following drugs causes heterochromia iridis?

A. Latanoprost (Correct Answer)
B. Prednisolone
C. Timolol
D. Olopatadine

Explanation: **Explanation:** **Latanoprost** is a Prostaglandin F2α (PGF2α) analogue used as a first-line treatment for Open-Angle Glaucoma. The correct answer is Latanoprost because it is well-known to cause **increased iris pigmentation**, leading to **heterochromia iridis** (a difference in coloration between the two eyes, especially if used unilaterally). * **Mechanism:** Latanoprost increases the amount of melanin within stromal melanocytes of the iris by stimulating the enzyme **tyrosinase**. It does not increase the number of melanocytes (no hyperplasia) but rather increases the pigmentation within existing cells. This change is typically permanent. **Analysis of Incorrect Options:** * **B. Prednisolone:** A corticosteroid used to treat ocular inflammation. Its primary ocular side effects are the formation of **posterior subcapsular cataracts** and **steroid-induced glaucoma** (due to decreased aqueous outflow). * **C. Timolol:** A non-selective beta-blocker. It reduces aqueous production. Common side effects include stinging, bradycardia, and bronchospasm, but it does not affect iris color. * **D. Olopatadine:** A dual-action antihistamine and mast cell stabilizer used for allergic conjunctivitis. It does not cause pigmentary changes. **High-Yield Clinical Pearls for NEET-PG:** 1. **Prostaglandin Analogue Side Effects:** Remember the triad: **Iris pigmentation**, **Hypertrichosis** (increased eyelash length/thickness), and **Periorbitopathy** (sunken eyes due to fat atrophy). 2. **Reversibility:** While eyelash changes are reversible upon discontinuation, **iris darkening is permanent**. 3. **Contraindication:** Avoid in patients with active uveitis or cystoid macular edema (CME), as prostaglandins are pro-inflammatory.

Question 17: Which drug is not deposited in the cornea?

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

Explanation: **Explanation:** The cornea often acts as a reservoir for systemic drugs due to its avascular nature and specific metabolic properties. This question tests your knowledge of **Corneal Verticillata (Vortex Keratopathy)** and other drug-induced deposits. **Why Antimony is the correct answer:** Antimony is a heavy metal used in the treatment of Leishmaniasis. Unlike other heavy metals (like Gold or Silver), it does **not** have a documented predilection for depositing in the corneal stroma or epithelium. Therefore, it does not cause clinical corneal opacification. **Analysis of Incorrect Options:** * **Gold (Chrysiasis):** Systemic administration of gold salts (used for rheumatoid arthritis) leads to fine, dust-like purple or brownish deposits in the **posterior corneal stroma**. * **Chloroquine:** This is a classic cause of **Corneal Verticillata**. It deposits in the basal epithelial layer in a whorl-like pattern. While it causes keratopathy, it is more famous for "Bull’s eye maculopathy." * **Amiodarone:** An anti-arrhythmic drug that causes Corneal Verticillata in nearly 100% of patients on long-term therapy. The deposits are usually asymptomatic and do not require drug discontinuation. **High-Yield NEET-PG Pearls:** 1. **Mnemonic for Vortex Keratopathy (CHAI-T):** **C**hloroquine/Hydroxychloroquine, **H**eamiodarone (Amiodarone), **A**ndrogens (Indomethacin), **I**be (Tamoxifen). *Note: Fabry’s disease is the most common systemic disease cause.* 2. **Silver (Argyrosis):** Causes slate-grey discoloration of the deep stroma and Descemet’s membrane. 3. **Copper (Chalcosis):** Deposits in **Descemet’s membrane**, forming the characteristic **Kayser-Fleischer (KF) ring** seen in Wilson’s disease. 4. **Iron (Siderosis):** Can deposit as a **Ferry’s line** (near surgical blebs) or **Stockers line** (near pterygium).

Question 18: In a case of anisocoria, when 1% pilocarpine solution is instilled into the eye with an abnormally dilated pupil, and no response occurs, what is the most likely cause of the anisocoria?

A. Adie's pupil
B. Horner's syndrome
C. Pharmacological blockade (Correct Answer)
D. Uncal herniation

Explanation: This question tests your understanding of the **pharmacological localization of anisocoria**, specifically the evaluation of a "fixed and dilated" pupil. ### **Explanation** The correct answer is **Pharmacological blockade**. Pilocarpine is a direct-acting parasympathomimetic (muscarinic agonist) that acts directly on the iris sphincter muscle to cause miosis. * In a normal eye or an eye with denervation supersensitivity (like Adie’s), 1% pilocarpine will cause immediate constriction. * If the pupil **fails to constrict** even with 1% pilocarpine, it indicates that the muscarinic receptors on the iris sphincter are physically blocked by an anticholinergic agent (e.g., Atropine, Tropicamide, or accidental exposure to Datura). This is the definitive test to differentiate pharmacological mydriasis from neurological causes. ### **Why other options are incorrect:** * **Adie’s Pupil:** This is due to post-ganglionic parasympathetic denervation. These pupils are hypersensitive and will constrict significantly even with **dilute (0.125%) pilocarpine** (Denervation Supersensitivity). * **Horner’s Syndrome:** This involves a **miotic (small)** pupil due to sympathetic palsy. The question describes an abnormally dilated pupil. * **Uncal Herniation (3rd Nerve Palsy):** In a compressive CN III palsy, the pre-ganglionic parasympathetic fibers are damaged. However, the iris sphincter muscle itself remains healthy and responsive. Therefore, 1% pilocarpine **will** cause constriction in a 3rd nerve palsy. ### **High-Yield Clinical Pearls for NEET-PG:** 1. **Step 1 (Dilute Pilocarpine 0.125%):** Constriction = Adie’s Pupil; No constriction = Normal or 3rd Nerve Palsy or Blockade. 2. **Step 2 (Standard Pilocarpine 1%):** Constriction = 3rd Nerve Palsy; No constriction = Pharmacological Blockade. 3. **Traumatic Mydriasis:** A pupil dilated due to sphincter tear (iridodialysis) will also fail to constrict with pilocarpine, but is usually identified by history and slit-lamp exam.

Question 19: What is the most common adverse effect of oral contraceptives?

A. Colour blindness
B. Optic neuritis (Correct Answer)
C. Ringscotoma
D. Nystagmus

Explanation: **Explanation:** Oral contraceptives (OCPs) are known to have various systemic and ocular side effects, primarily due to their estrogen and progesterone components. Among the ocular complications, **Optic Neuritis** is considered a significant and documented adverse effect. **1. Why Optic Neuritis is correct:** The underlying mechanism is linked to the **pro-thrombotic and vasculopathic effects** of estrogen. OCPs increase the risk of thromboembolic events, which can lead to vascular compromise of the optic nerve head or trigger an inflammatory response (Papillitis or Retrobulbar neuritis). While rare in absolute terms, among the options provided, it is the most classically associated neuro-ophthalmic complication of OCP use. **2. Analysis of Incorrect Options:** * **A. Colour blindness:** This is typically a congenital condition (X-linked recessive) or acquired due to specific drugs like Ethambutol or Digoxin. OCPs do not typically cause primary color vision defects. * **C. Ring scotoma:** This is a characteristic visual field defect seen in **Retinitis Pigmentosa** or as a side effect of **Chloroquine/Hydroxychloroquine** toxicity. * **D. Nystagmus:** This is usually a sign of cerebellar or vestibular dysfunction, or toxicity from drugs like Phenytoin or Carbamazepine, but not OCPs. **Clinical Pearls for NEET-PG:** * **Most common ocular side effect of OCPs:** Contact lens intolerance (due to changes in the tear film and corneal curvature/edema). * **Vascular risks:** OCPs are associated with an increased risk of **Central Retinal Vein Occlusion (CRVO)** and **Pseudotumor Cerebri** (Idiopathic Intracranial Hypertension), which presents with bilateral papilledema. * Always screen for a history of OCP use in young females presenting with sudden vision loss or signs of raised intracranial pressure.

Question 20: What is the pathognomonic sign of Acute Iridocyclitis?

A. Aqueous flare
B. Keratic precipitates (Correct Answer)
C. Small pupil
D. All of the above

Explanation: **Explanation:** **Keratic Precipitates (KPs)** are considered the pathognomonic sign of acute iridocyclitis (anterior uveitis). They are cellular deposits (leukocytes and inflammatory debris) found on the posterior surface of the corneal endothelium. Their presence confirms active or past intraocular inflammation, as they are not found in a healthy eye. **Analysis of Options:** * **Keratic Precipitates (Correct):** These are the hallmark of iridocyclitis. Their distribution (typically in **Arlt’s triangle**) and morphology (e.g., "Mutton-fat" KPs in granulomatous uveitis) provide crucial diagnostic clues. * **Aqueous Flare (Incorrect):** While flare (due to protein leakage from damaged iris vessels) is a cardinal sign of inflammation, it is not pathognomonic. It can also be seen in conditions like ocular ischemia or post-surgery without active iridocyclitis. * **Small Pupil (Incorrect):** Miosis occurs due to iris sphincter spasm and irritation. While a common clinical finding in acute cases, it is a non-specific sign and can occur in various other conditions like corneal abrasions or chemical injuries. **High-Yield Clinical Pearls for NEET-PG:** 1. **Arlt’s Triangle:** The base-down triangular distribution of KPs due to convection currents in the aqueous humor. 2. **Mutton-fat KPs:** Large, greasy-looking precipitates composed of epithelioid cells and macrophages; characteristic of **Granulomatous Uveitis** (e.g., Sarcoidosis, TB). 3. **Fine KPs:** Composed of neutrophils and lymphocytes; characteristic of **Non-granulomatous Uveitis**. 4. **Koeppe and Busacca Nodules:** Inflammatory cell clusters on the pupillary margin and iris stroma, respectively, often seen in granulomatous cases.

Practice by Chapter

Ocular Pharmacokinetics

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Anti-infective Agents

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Anti-inflammatory Drugs

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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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