Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology Indian Medical PG Practice Questions and MCQs

Question 151: Which of the following is the drug of choice for the treatment of corneal ulcers caused by filamentous fungi?

A. Itraconazole
B. Natamycin (Correct Answer)
C. Nystatin
D. Fluconazole

Explanation: **Explanation:** The drug of choice for fungal keratitis caused by **filamentous fungi** (such as *Aspergillus* and *Fusarium*) is **Natamycin (5% ophthalmic suspension)**. **Why Natamycin is the Correct Choice:** Natamycin is a polyene antifungal that works by binding to ergosterol in the fungal cell membrane, leading to cell lysis. It is the only FDA-approved topical antifungal for ophthalmic use. Its efficacy is particularly high against filamentous organisms, which are the most common cause of fungal corneal ulcers in tropical climates and following trauma with vegetative matter. **Analysis of Incorrect Options:** * **Itraconazole:** While effective against some fungi, it has poor ocular penetration when used topically. It is generally reserved as an oral adjunct for deep or recalcitrant stromal infections. * **Nystatin:** Also a polyene, but it is primarily effective against *Candida* (yeast). It is not the first-line treatment for filamentous fungi and is rarely used in modern ophthalmology due to the superior profile of Natamycin. * **Fluconazole:** This is a triazole that is highly effective against **yeasts** (like *Candida* species) but has limited activity against filamentous fungi. It is often used topically or systemically for *Candida* keratitis. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Natamycin is the first-line treatment for filamentous fungal keratitis (especially *Fusarium*). * **Amphotericin B (0.15%):** This is the drug of choice for **yeast-related (Candida)** corneal ulcers. * **Clinical Sign:** Fungal ulcers typically present with "feathery borders," "satellite lesions," and a "dry, immune ring." * **Contraindication:** Topical steroids are strictly contraindicated in active fungal keratitis as they worsen the infection.

Question 152: Herpetic keratitis is treated by:

A. Analgesics
B. Atropine
C. Steroids
D. Idoxuridine (Correct Answer)

Explanation: **Explanation:** **1. Why Idoxuridine is Correct:** Herpetic keratitis is caused by the **Herpes Simplex Virus (HSV)**. The mainstay of treatment is antiviral therapy. **Idoxuridine** was the first antiviral agent developed for clinical use; it is a pyrimidine analogue that inhibits viral DNA synthesis by substituting for thymidine. While newer drugs like Acyclovir and Ganciclovir are now preferred due to lower toxicity, Idoxuridine remains the classic pharmacological answer for treating epithelial HSV keratitis. **2. Why Other Options are Incorrect:** * **Analgesics (A):** While they may provide symptomatic relief for pain, they do not treat the underlying viral infection. * **Atropine (B):** Atropine is a cycloplegic used as an *adjunct* therapy in keratitis to relieve ciliary spasms and prevent posterior synechiae, but it is not the primary curative treatment. * **Steroids (C):** **Contraindicated** in active epithelial (dendritic) herpetic keratitis. Steroids promote viral replication and can lead to the formation of a "Geographic ulcer" or even corneal perforation. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Topical **Acyclovir (3%)** or **Ganciclovir (0.15%)** are currently the drugs of choice. * **Classic Sign:** The hallmark of HSV epithelial keratitis is the **Dendritic Ulcer** (linear branching with terminal bulbs), which stains with Fluorescein. * **The "Steroid Rule":** Never use steroids in a dendritic ulcer. Steroids are only used in *Stromal* (Disciform) keratitis under strict antiviral cover. * **Trifluorothymidine (Trifluridine):** Another antiviral used, especially for cases resistant to Idoxuridine.

Question 153: Which of the following agents is NOT anti-VEGF?

A. Pegaptanib
B. 5-Fluorouracil (Correct Answer)
C. Bevacizumab
D. Ranibizumab

Explanation: **Explanation:** The correct answer is **5-Fluorouracil (5-FU)**. **Why 5-Fluorouracil is the correct answer:** 5-Fluorouracil is an **antimetabolite** (pyrimidine analogue) that inhibits the enzyme thymidylate synthase, thereby interfering with DNA synthesis. In ophthalmology, it is primarily used as an **anti-fibrotic agent** during glaucoma filtration surgery (trabeculectomy) to prevent subconjunctival scarring and bleb failure. It does not target Vascular Endothelial Growth Factor (VEGF). **Analysis of Incorrect Options (Anti-VEGF Agents):** * **Pegaptanib:** This was the first FDA-approved anti-VEGF for neovascular AMD. It is an RNA aptamer that specifically binds to the VEGF-165 isoform. * **Bevacizumab:** A recombinant humanized monoclonal antibody that binds to all isoforms of VEGF-A. While used "off-label" in ophthalmology, it is widely utilized for conditions like diabetic retinopathy and wet AMD due to its cost-effectiveness. * **Ranibizumab:** A humanized monoclonal antibody fragment (Fab) designed specifically for ocular use. It has a high affinity for all active isoforms of VEGF-A. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Anti-VEGF:** These agents inhibit angiogenesis and reduce vascular permeability by blocking VEGF, a key mediator in neovascularization. * **Common Indications:** Wet Age-Related Macular Degeneration (AMD), Diabetic Macular Edema (DME), and Central Retinal Vein Occlusion (CRVO). * **Other Anti-VEGFs to remember:** **Aflibercept** (a "VEGF Trap" that binds VEGF-A, VEGF-B, and Placental Growth Factor) and **Brolucizumab**. * **5-FU vs. Mitomycin-C:** Both are used in trabeculectomy, but Mitomycin-C is a more potent alkylating agent often preferred for high-risk cases.

Question 154: Which drug is used in the management of glaucoma?

A. Propranolol
B. Atenolol
C. Timolol (Correct Answer)
D. Pindolol

Explanation: **Explanation:** **Timolol** is the correct answer as it is a non-selective beta-adrenergic antagonist and a first-line agent in the medical management of Open-Angle Glaucoma. **Mechanism of Action:** In the eye, beta-2 receptors are located on the ciliary epithelium. Their activation normally stimulates the production of aqueous humor. Timolol blocks these receptors, leading to a **decrease in aqueous humor production**, thereby lowering intraocular pressure (IOP). Unlike miotics, it does not affect pupil size or accommodation. **Analysis of Incorrect Options:** * **Propranolol (A):** While it is a non-selective beta-blocker, it possesses significant **membrane-stabilizing activity (local anesthetic effect)**. If used topically in the eye, it would anesthetize the cornea, leading to a loss of the protective blink reflex and increasing the risk of corneal ulcers. * **Atenolol (B):** This is a cardioselective (Beta-1) blocker. Since aqueous production is primarily mediated by Beta-2 receptors, Beta-1 selective blockers are less effective at lowering IOP. * **Pindolol (D):** This drug has **Intrinsic Sympathomimetic Activity (ISA)**. Because it partially stimulates the receptor while blocking it, it is less effective at reducing aqueous secretion compared to pure antagonists like Timolol. **High-Yield Pearls for NEET-PG:** * **Betaxolol:** The only **cardioselective (B1)** beta-blocker used in glaucoma. It is safer for patients with mild asthma but less efficacious than Timolol. * **Contraindications:** Topical beta-blockers undergo systemic absorption via the nasolacrimal duct. They are strictly contraindicated in patients with **Bronchial Asthma, COPD, Bradycardia, and Heart Block**. * **Tip:** To minimize systemic side effects, advise patients to perform **punctal occlusion** for 2 minutes after instilling drops.

Question 155: Which drug can induce iris cysts?

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

Explanation: **Explanation:** **Correct Option: D. Ecothiopate** Ecothiopate is a potent, long-acting **irreversible cholinesterase inhibitor** (miotic). The formation of **iris cysts** (specifically at the pupillary margin) is a classic side effect associated with long-term use of strong miotics, particularly the anticholinesterases. These cysts arise due to the hypertrophy of the pigment epithelium of the iris. In pediatric practice, where ecothiopate is sometimes used for accommodative esotropia, the concomitant use of **Phenylephrine (2.5%)** can prevent the formation of these cysts. **Analysis of Incorrect Options:** * **A. Atropine:** This is a parasympatholytic (mydriatic-cycloplegic) drug. It causes pupillary dilation and paralysis of accommodation, rather than the epithelial proliferation seen with miotics. * **B. Pilocarpine:** While pilocarpine is a direct-acting miotic, iris cysts are significantly rarer compared to the potent indirect-acting agents like Ecothiopate or Isoflurophate. * **C. Phenylephrine:** This is a sympathomimetic mydriatic. Interestingly, it is the *preventative* agent for iris cysts rather than the cause. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Ecothiopate:** It phosphorylates the enzyme acetylcholinesterase. * **Systemic Side Effect:** It significantly reduces **plasma pseudocholinesterase** levels. This is critical for anesthesia; if a patient on Ecothiopate is given **Succinylcholine**, it can lead to prolonged apnea. * **Other Ocular Side Effects:** Long-term use is associated with "miotic cysts," anterior subcapsular cataracts, and an increased risk of retinal detachment. * **Antidote:** Pralidoxime (2-PAM) can reactivate the enzyme if administered before "aging" occurs.

Question 156: Which of the following agents is NOT used in the treatment of Diabetic Macular Edema?

A. Ruboxistaurin
B. Pyridazinones
C. Benfotiamine
D. Tamoxifen (Correct Answer)

Explanation: **Explanation:** The correct answer is **Tamoxifen**. In fact, Tamoxifen is known to **cause** maculopathy rather than treat it. Tamoxifen-induced maculopathy is characterized by bilateral, fine, glistening crystalline deposits in the inner retinal layers (paramacular area), which can lead to macular edema and decreased visual acuity. **Why the other options are incorrect (Agents used in DME management):** * **Ruboxistaurin:** This is a selective **Protein Kinase C (PKC-beta) inhibitor**. Hyperglycemia activates the PKC pathway, leading to increased vascular permeability and VEGF expression. Ruboxistaurin aims to block this pathway to reduce macular edema. * **Pyridazinones:** These act as **Aldose Reductase Inhibitors (ARIs)**. They inhibit the polyol pathway, preventing the accumulation of sorbitol, which causes osmotic stress and microvascular damage in the diabetic retina. * **Benfotiamine:** A lipid-soluble derivative of Thiamine (Vitamin B1). It inhibits three major pathways of hyperglycemic damage: the hexosamine pathway, the advanced glycation end-product (AGE) pathway, and the PKC pathway by activating the enzyme **transketolase**. **High-Yield Clinical Pearls for NEET-PG:** * **First-line treatment for DME:** Intravitreal Anti-VEGF agents (e.g., Ranibizumab, Aflibercept). * **Tamoxifen Toxicity:** Look for "crystalline maculopathy" in the history of a patient being treated for breast cancer. * **Other drugs causing Crystalline Maculopathy:** Canthaxanthin (tanning pills), Talc (IV drug abuse), and Methoxyflurane. * **Steroids in DME:** Intravitreal implants (Dexamethasone/Ozurdex) are used, especially in pseudophakic eyes or those refractory to Anti-VEGF.

Question 157: Which drug is known to cause cataracts?

A. Amikacin
B. Dexamethasone (Correct Answer)
C. Chloramphenicol
D. Penicillin

Explanation: **Explanation:** **Dexamethasone** is a potent corticosteroid. The most characteristic ocular side effect of long-term corticosteroid use (whether topical, systemic, or inhaled) is the development of a **Posterior Subcapsular Cataract (PSC)**. **Mechanism:** Steroids are thought to interfere with the sodium-potassium pump in the lens epithelium and alter the transcription of lens crystallins. This leads to the migration of lens epithelial cells to the posterior pole, resulting in the formation of opacities. Additionally, steroids are a well-known cause of **secondary open-angle glaucoma** due to increased resistance to aqueous outflow at the trabecular meshwork. **Analysis of Incorrect Options:** * **Amikacin (Option A):** An aminoglycoside primarily associated with **macular infarction** (retinal toxicity) if injected intravitreally. * **Chloramphenicol (Option C):** While it can cause systemic bone marrow suppression, its primary ocular side effect is **optic neuritis/atrophy**, not cataracts. * **Penicillin (Option D):** Generally lacks significant ocular toxicity; it is more commonly associated with systemic hypersensitivity reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Steroid-Induced Cataract:** Classically **Posterior Subcapsular (PSC)**. It is dose and duration-dependent. * **Steroid Responders:** Approximately 5-10% of the population shows a significant rise in Intraocular Pressure (IOP) after steroid use. * **Other Drugs causing Cataracts:** Chlorpromazine (stellate/star-shaped), Busulfan, Amiodarone, and Quetiapine. * **Mnemonic for PSC:** "Steroids, Diabetes, and Radiation" are the three most common causes of Posterior Subcapsular Cataracts.

Question 158: Which of the following prostaglandin analogues is used in the management of glaucoma?

A. Misoprostol
B. Latanoprost (Correct Answer)
C. Enprostil
D. Rioprostil

Explanation: **Explanation:** **Latanoprost** is the correct answer as it is a synthetic **Prostaglandin F2α (PGF2α) analogue** specifically designed for ophthalmic use. In the management of Open-Angle Glaucoma (OAG) and Ocular Hypertension, Latanoprost acts by **increasing the uveoscleral outflow** of aqueous humor, thereby reducing intraocular pressure (IOP). It is often considered a first-line agent due to its once-daily dosing and potent efficacy. **Analysis of Incorrect Options:** * **Misoprostol (Option A):** A PGE1 analogue primarily used for preventing NSAID-induced gastric ulcers and for medical abortion/labor induction. * **Enprostil (Option B) & Rioprostil (Option D):** These are PGE analogues historically studied for their antisecretory and cytoprotective effects on the gastric mucosa to treat peptic ulcers; they have no clinical application in ophthalmology. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Increases uveoscleral outflow (not trabecular outflow). * **Side Effects (High Yield):** 1. **Hypertrichosis:** Increased length, thickness, and pigmentation of eyelashes (Bimatoprost is FDA-approved for this as *Latisse*). 2. **Iris Hyperpigmentation:** Permanent darkening of the iris (brown discoloration). 3. **Cystoid Macular Edema (CME):** Use with caution in aphakic or pseudophakic patients. 4. **Prostaglandin-associated Periorbitopathy:** Sunken eyes due to fat atrophy. * **Other Analogues:** Travoprost, Bimatoprost (a prostamide), and Tafluprost. * **Contraindication:** Active intraocular inflammation (e.g., Uveitis).

Question 159: Which of the following medications is NOT typically administered as eye drops for a corneal ulcer?

A. Chloramphenicol
B. Methylcellulose
C. Flurometholone (Correct Answer)
D. Olopatadine

Explanation: **Explanation:** The management of a corneal ulcer (keratitis) focuses on treating the underlying infection and promoting epithelial healing. **Fluorometholone** is a topical corticosteroid. In the acute phase of a corneal ulcer, steroids are generally **contraindicated** because they inhibit collagen synthesis and suppress the local immune response. This can lead to the worsening of the infection, delayed wound healing, and even corneal perforation (melting). Steroids are only considered in specific bacterial cases once the infection is controlled, to reduce scarring. **Analysis of Options:** * **Chloramphenicol (Option A):** A broad-spectrum bacteriostatic antibiotic frequently used as first-line prophylaxis or treatment for bacterial corneal ulcers. * **Methylcellulose (Option B):** A lubricating agent (artificial tears) used to maintain ocular surface integrity and promote re-epithelialization by reducing friction. * **Olopatadine (Option C):** An antihistamine/mast cell stabilizer. While primarily for allergic conjunctivitis, it is not contraindicated in an ulcer and does not impede healing like steroids do. **Clinical Pearls for NEET-PG:** * **Steroid Contraindication:** Never use steroids in a dendritic ulcer (Herpes Simplex Keratitis) as it leads to a "Geographic ulcer." * **Fortified Antibiotics:** For severe bacterial ulcers, "fortified" drops (e.g., Cefazolin 5% or Tobramycin 1.4%) are preferred over standard strengths. * **Atropine (1%):** Often added to the regimen to relieve ciliary spasm (pain) and prevent posterior synechiae formation. * **Natamycin (5%):** The drug of choice for filamentous fungal corneal ulcers.

Question 160: Bull's eye maculopathy is an adverse effect caused by which of the following medications?

A. Chloroquine (Correct Answer)
B. Lumefantrine
C. Quinine
D. Primaquine

Explanation: **Explanation:** **Bull’s eye maculopathy** is a classic, high-yield ocular side effect primarily associated with the long-term use of **Chloroquine (CQ)** and its derivative, **Hydroxychloroquine (HCQ)**. **Why Chloroquine is correct:** Chloroquine has a high affinity for melanin-containing tissues, leading to its accumulation in the **Retinal Pigment Epithelium (RPE)**. It inhibits lysosomal enzymes within the RPE, causing metabolic stress and subsequent degeneration of the photoreceptors. Clinically, this manifests as a central island of spared RPE surrounded by a ring of depigmentation (atrophy), which is further encircled by a ring of normal pigmentation—resembling a **"Bull’s Eye."** On Fundus Fluorescein Angiography (FFA), this appears as a "window defect." **Why the other options are incorrect:** * **Lumefantrine:** Used in combination therapy for malaria (ACT), it does not have significant documented retinal toxicity. * **Quinine:** While toxic to the eye, Quinine causes **"Quinine Amblyopia,"** characterized by sudden vision loss, profound retinal arteriolar narrowing (vasospasm), and optic atrophy, rather than a bull’s eye pattern. * **Primaquine:** Primarily associated with systemic side effects like hemolysis in G6PD-deficient patients; it does not cause maculopathy. **NEET-PG High-Yield Pearls:** 1. **Screening:** The most sensitive early tests for HCQ/CQ toxicity are **Automated Visual Fields (10-2)** and **Spectral Domain OCT** (showing the "Flying Saucer" sign). 2. **Dosage:** Toxicity risk increases significantly when the daily dose of HCQ exceeds **5 mg/kg** of real body weight. 3. **Irreversibility:** Once Bull’s eye maculopathy is visible on fundoscopy, the damage is usually **permanent and may progress** even after stopping the drug (washout effect). 4. **Other causes of Bull's Eye Maculopathy:** Stargardt’s disease, Cone-Dystrophy, and Batten’s disease.

Practice by Chapter

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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