Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology Indian Medical PG Practice Questions and MCQs

Question 31: Chronic use of systemic steroids most commonly leads to which ocular complication?

A. Cataract (Correct Answer)
B. Glaucoma
C. Uveitis
D. Conjunctival and lid papillomatosis

Explanation: **Explanation:** **Correct Answer: A. Cataract** Systemic steroid therapy (oral or injectable) is most strongly associated with the development of **Posterior Subcapsular Cataract (PSC)**. The underlying mechanism involves the binding of steroids to lens crystallin proteins, leading to protein aggregation and the disruption of lens fiber clarity. While both systemic and topical steroids can cause cataracts, systemic administration carries a higher relative risk for PSC compared to other ocular complications. **Analysis of Incorrect Options:** * **B. Glaucoma:** While steroids can cause "steroid-induced glaucoma" by increasing resistance to aqueous outflow at the trabecular meshwork, this is significantly **more common with topical (drops/ointments)** or periocular administration than with systemic use. * **C. Uveitis:** Steroids are actually the primary treatment for uveitis due to their potent anti-inflammatory properties; they do not cause it. * **D. Conjunctival and lid papillomatosis:** This is not a recognized side effect of steroid therapy. Steroids are more likely to cause thinning of the skin (atrophy) or secondary infections (fungal/viral) due to local immunosuppression. **High-Yield Clinical Pearls for NEET-PG:** * **Cataract Type:** Steroid-induced cataracts are typically **bilateral** and **Posterior Subcapsular**. * **Glaucoma Risk:** The "Steroid Responder" phenomenon (increased IOP) is most prevalent with topical **Dexamethasone** and least with **Fluorometholone** or **Loteprednol**. * **Other Systemic Side Effects:** Long-term use can also lead to Central Serous Chorioretinopathy (CSCR) and delayed wound healing. * **Pediatric Note:** Children are more susceptible to rapid steroid-induced IOP spikes than adults.

Question 32: Which of the following is not a contraindication for timolol?

A. Bronchial asthma
B. Anxiety (Correct Answer)
C. Myocardial infarction
D. Thyrotoxicosis

Explanation: **Explanation:** Timolol is a **non-selective beta-blocker** (blocking both $\beta_1$ and $\beta_2$ receptors) commonly used as a first-line topical treatment for glaucoma. Its systemic absorption via the nasolacrimal duct can lead to significant side effects, making its contraindications a high-yield topic for NEET-PG. **Why Anxiety is the Correct Answer:** Anxiety is **not** a contraindication; in fact, systemic beta-blockers are often used off-label to treat the peripheral autonomic symptoms of performance anxiety (e.g., palpitations, tremors). Timolol does not worsen anxiety and has no pharmacological reason to be avoided in these patients. **Analysis of Contraindications (Incorrect Options):** * **Bronchial Asthma:** Timolol blocks $\beta_2$ receptors in the lungs, leading to bronchoconstriction. It is strictly contraindicated in asthma and severe COPD as it can precipitate a fatal bronchospasm. * **Myocardial Infarction (MI) & Heart Block:** As a $\beta_1$ blocker, it has negative inotropic and chronotropic effects. It is contraindicated in patients with bradycardia, second or third-degree heart block, and overt cardiac failure. * **Thyrotoxicosis:** While beta-blockers treat symptoms of hyperthyroidism, Timolol can **mask the clinical signs** (like tachycardia) of an impending thyrotoxic crisis (thyroid storm), making clinical monitoring difficult. **High-Yield Clinical Pearls for NEET-PG:** * **Betaxolol:** The only **$\beta_1$ selective (cardioselective)** topical beta-blocker. It is safer (though not absolute) in patients with mild respiratory issues. * **Nasolacrimal Occlusion:** Advise patients to apply pressure over the lacrimal sac for 2-3 minutes after instillation to minimize systemic absorption and side effects. * **Metabolic Effect:** Timolol can mask symptoms of **hypoglycemia** in diabetic patients.

Question 33: Cholinergic drugs such as pilocarpine are routinely used to treat glaucoma. What is their mechanism of action in the eye that accounts for this ophthalmologic use?

A. Reduction in the formation of aqueous humor
B. Blockade of adrenergic receptors to potentiate cholinergic effects
C. Alkalinization of aqueous humor
D. Improved drainage of aqueous humor (Correct Answer)

Explanation: **Explanation:** Pilocarpine is a direct-acting parasympathomimetic (cholinergic) drug. Its primary mechanism in treating glaucoma involves the stimulation of **muscarinic (M3) receptors** on the **sphincter pupillae** and the **ciliary muscle**. 1. **Why Option D is Correct:** When the ciliary muscle contracts, it pulls on the **scleral spur**. This mechanical action opens up the pores of the **trabecular meshwork**, thereby increasing the outflow (drainage) of aqueous humor into the Canal of Schlemm. In angle-closure glaucoma, the induced miosis (pupillary constriction) also pulls the peripheral iris away from the trabecular meshwork, opening the anatomical angle. 2. **Why Incorrect Options are Wrong:** * **Option A:** Reduction of aqueous formation is the mechanism of **Beta-blockers** (e.g., Timolol), **Alpha-2 agonists** (e.g., Brimonidine), and **Carbonic Anhydrase Inhibitors** (e.g., Acetazolamide). * **Option B:** Pilocarpine is a cholinergic agonist, not an adrenergic blocker. Adrenergic blockade (Beta-blockers) reduces production rather than potentiating cholinergic drainage. * **Option C:** The pH of aqueous humor is not the therapeutic target for glaucoma drugs; alkalinization does not lower intraocular pressure. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Pilocarpine is the drug of choice for **Acute Angle Closure Glaucoma** (to break the attack after initial pressure reduction). * **Side Effects:** Brow ache (due to ciliary spasm), induced myopia, and decreased night vision (due to miosis). * **Contraindication:** Avoid in young patients (risk of retinal detachment) and patients with cataracts (miosis further obscures vision).

Question 34: What is the most common site of nasolacrimal duct blockade caused by anti-glaucoma medications?

A. Opening of the duct into the nose
B. Superior canaliculus (Correct Answer)
C. Inferior canaliculus
D. Common canaliculus

Explanation: **Explanation:** The chronic use of certain topical anti-glaucoma medications, most notably **Echothiophate (a miotic)** and occasionally **Timolol or Epinephrine**, can lead to cicatricial changes in the lacrimal drainage system. **Why the Superior Canaliculus is correct:** While drug-induced stenosis can affect any part of the proximal lacrimal system, clinical studies and anatomical observations indicate that the **superior canaliculus** is the most frequent site of medication-induced obstruction. This is attributed to the local toxic effect of the drug (or its preservative, like Benzalkonium chloride) causing chronic subclinical inflammation, which leads to progressive fibrosis and eventual stenosis of the canalicular lumen. **Analysis of Incorrect Options:** * **Inferior Canaliculus:** Although the inferior canaliculus carries about 70% of the tear volume, it is statistically less frequently involved in drug-induced isolated blockade compared to the superior canaliculus. * **Common Canaliculus:** While stenosis can occur here, it usually follows involvement of the individual canaliculi. * **Opening of the duct into the nose:** Blockage at the Valve of Hasner (distal NLD) is typically congenital or related to chronic dacryocystitis/involutional changes, rather than topical drug toxicity. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most common drug causing canalicular stenosis:** Echothiophate (Irreversible acetylcholinesterase inhibitor). 2. **Preservative Toxicity:** Benzalkonium chloride (BAK) in eye drops is a major culprit for ocular surface disease and secondary scarring of the puncta/canaliculi. 3. **Primary Acquired Nasolacrimal Duct Obstruction (PANDO):** More common in elderly females; the most common site of *idiopathic* obstruction is the NLD itself, not the canaliculi. 4. **Management:** If stenosis is detected early, stopping the offending drug and inserting silicone stents may prevent total occlusion.

Question 35: Bevacizumab is used in which of the following conditions?

A. Diabetic retinopathy (Correct Answer)
B. Glaucoma
C. Diabetic nephropathy
D. Neuropathy

Explanation: **Explanation:** **Bevacizumab** (Avastin) is a recombinant humanized monoclonal antibody that binds to and inhibits **Vascular Endothelial Growth Factor (VEGF)**. In the context of Ophthalmology, it is used off-label as an intravitreal injection to treat vasoproliferative retinal diseases. **Why Diabetic Retinopathy is Correct:** In **Diabetic Retinopathy (DR)**, chronic hyperglycemia leads to retinal ischemia, which triggers the release of VEGF. This results in two major complications: **Diabetic Macular Edema (DME)** (increased vascular permeability) and **Proliferative Diabetic Retinopathy (PDR)** (neovascularization). By neutralizing VEGF, Bevacizumab reduces macular swelling and causes regression of fragile new blood vessels, preventing vitreous hemorrhage and tractional retinal detachment. **Why Other Options are Incorrect:** * **Glaucoma:** While anti-VEGFs are used in *Neovascular Glaucoma* to shrink iris vessels, they are not a treatment for primary open-angle or closed-angle glaucoma. * **Diabetic Nephropathy & Neuropathy:** These are microvascular complications of diabetes, but Bevacizumab is not used to treat them. Nephropathy involves basement membrane thickening and podocyte loss, while neuropathy involves nerve ischemia; neither is currently managed with VEGF inhibitors. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** VEGF-A inhibitor. * **Other Ocular Indications:** Wet Age-Related Macular Degeneration (ARMD), Central Retinal Vein Occlusion (CRVO), and Retinopathy of Prematurity (ROP). * **Comparison:** Unlike **Ranibizumab** (Fab fragment) and **Aflibercept** (decoy receptor), Bevacizumab is a full-length antibody and is significantly more cost-effective for clinical use. * **Side Effects:** Endophthalmitis (most serious post-injection complication) and transient rise in intraocular pressure.

Question 36: Bulls eye retinopathy is seen in toxicity of which drug?

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

Explanation: **Explanation:** **Bull’s Eye Maculopathy** is a classic clinical finding characterized by a central area of hyperpigmentation (foveolar) surrounded by a zone of depigmentation (atrophy of the RPE), which is further encircled by a ring of hyperpigmentation. **1. Why Chloroquine (CQ) is correct:** Chloroquine and its derivative, Hydroxychloroquine (HCQ), have a high affinity for **melanin** in the Retinal Pigment Epithelium (RPE). The drug binds to melanin, leading to RPE atrophy and secondary degeneration of the overlying photoreceptors. On fundoscopy, this manifests as the "Bull's Eye" appearance. While HCQ is more commonly used today, CQ has a higher risk of retinal toxicity at lower cumulative doses. **2. Why the other options are incorrect:** * **Mefloquine:** Primarily used for malaria prophylaxis; it is associated with neuropsychiatric side effects (dizziness, anxiety) rather than specific retinal toxicity. * **Primaquine:** Known for causing hemolytic anemia in G6PD-deficient patients; it does not cause maculopathy. * **Quinine:** Toxicity (Cinchonism) causes acute vision loss due to **retinal arteriolar narrowing** and "cherry red spot" appearance (toxic optic neuropathy), but not the chronic Bull’s Eye pattern. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign:** The earliest clinical sign of CQ/HCQ toxicity is a **granular appearance** of the macula or a subtle loss of the foveal reflex. * **Earliest Functional Change:** Increased threshold in the central 10 degrees of the visual field (detected by **Humphrey Visual Field 10-2**). * **Screening Gold Standard:** Spectral Domain Optical Coherence Tomography (SD-OCT) showing the **"Flying Saucer" sign** (preservation of central foveal outer retinal layers with peripheral loss). * **Other causes of Bull's Eye Maculopathy:** Stargardt’s disease, Cone dystrophy, and Spielmeyer-Vogt syndrome.

Question 37: Which of the following anti-glaucoma drugs can likely cause black pigmentation on the conjunctiva?

A. Adrenaline (Correct Answer)
B. Latanoprost
C. Beta blockers
D. Pilocarpine

Explanation: **Explanation:** **Correct Option: A (Adrenaline)** Adrenaline (Epinephrine) and its prodrug Dipivefrine are sympathomimetic agents that can cause **adrenochrome deposits** in the conjunctiva. These are small, discrete, black or dark-brown pigment spots. They occur due to the oxidation of adrenaline into melanin-like pigments, which get trapped in the conjunctival stroma or within small cysts. This is a classic high-yield side effect associated with long-term topical adrenaline use. **Incorrect Options:** * **B. Latanoprost:** While Prostaglandin analogues (PGAs) cause pigmentation, they typically cause **iris heterochromia** (darkening of the iris) and **eyelash darkening/thickening**, rather than discrete black conjunctival deposits. * **C. Beta blockers (e.g., Timolol):** These are the most common first-line drugs but are not associated with pigmentation. Their primary side effects are systemic (bradycardia, bronchospasm) and local (dry eye). * **D. Pilocarpine:** A miotic agent that causes side effects like miosis, brow ache, and "ciliary spasm." It does not cause conjunctival pigmentation. **High-Yield Clinical Pearls for NEET-PG:** 1. **Adrenochrome deposits:** Always associate "black spots on conjunctiva" with Adrenaline. 2. **Iris Pigmentation:** Prostaglandin analogues (Latanoprost) increase melanin synthesis in melanocytes (without increasing the number of melanocytes). 3. **Cystoid Macular Edema (CME):** Adrenaline is contraindicated in **aphakic patients** because it can precipitate CME. 4. **Bitot’s Spots vs. Adrenochrome:** Do not confuse these; Bitot’s spots are white/foamy (Vitamin A deficiency), while adrenochrome deposits are black/pigmented.

Question 38: Which antifungal agent is administered intravitreally for ocular infections?

A. Fluconazole
B. Amphotericin B (Correct Answer)
C. Itraconazole
D. Flucytosine

Explanation: **Explanation:** **Amphotericin B** is the gold standard for the intravitreal treatment of fungal endophthalmitis, particularly when caused by *Aspergillus* or *Candida* species. In cases of exogenous or endogenous endophthalmitis where the infection has breached the blood-retinal barrier or is introduced directly into the vitreous, systemic antifungals often fail to reach therapeutic concentrations. Intravitreal injection (standard dose: **5–10 µg in 0.1 mL**) ensures immediate, high-level bioavailability at the site of infection. **Analysis of Options:** * **Amphotericin B (Correct):** A polyene antifungal that binds to ergosterol in the fungal cell membrane. It is the preferred intravitreal agent due to its broad spectrum and established safety profile at low doses. * **Fluconazole:** While it has excellent ocular penetration when taken **systemically** (oral/IV), it is rarely used intravitreally because its spectrum is limited primarily to *Candida* and it lacks activity against filamentous fungi like *Aspergillus*. * **Itraconazole:** This is highly lipophilic with poor intraocular penetration. It is not formulated for intravitreal use due to solubility issues and potential retinal toxicity. * **Flucytosine:** Primarily used as an oral adjunct therapy. It is never used as monotherapy or as a primary intravitreal agent due to the rapid development of resistance. **High-Yield Clinical Pearls for NEET-PG:** * **Voriconazole (100 µg/0.1 mL):** This is the other major antifungal used intravitreally, often preferred over Amphotericin B for *Aspergillus* due to lower retinal toxicity. * **Natamycin (5%):** The drug of choice for **fungal keratitis** (topical), but it is **not** used intravitreally. * **Drug of Choice for Endophthalmitis:** For bacterial cases, the standard intravitreal "cocktail" is **Vancomycin + Ceftazidime**. For fungal cases, it is **Amphotericin B or Voriconazole**.

Question 39: What is the treatment of choice for Pars planitis?

A. Pilocarpine
B. Corticosteroid (Correct Answer)
C. Beta-blocker
D. NSAIDs

Explanation: **Explanation:** **Pars planitis** is a specific subset of intermediate uveitis characterized by inflammation of the pars plana, often associated with "snowball" (vitreous opacities) or "snowbank" formation (exudates on the pars plana). **1. Why Corticosteroids are the Correct Choice:** The primary goal in treating pars planitis is to suppress intraocular inflammation and prevent complications like Cystoid Macular Edema (CME), which is the most common cause of vision loss in these patients. **Corticosteroids** are the mainstay of treatment due to their potent anti-inflammatory and immunosuppressive properties. They are typically administered via the **Steere’s Ladder approach**: * **Periocular injections** (e.g., Posterior sub-Tenon triamcinolone) are often the first line for unilateral cases. * **Systemic steroids** are used for bilateral or resistant cases. * **Intravitreal implants** may be used for chronic management. **2. Why the Other Options are Incorrect:** * **Pilocarpine (A):** This is a miotic (parasympathomimetic) used in glaucoma. In uveitis, it is contraindicated as it can increase inflammation, promote the formation of posterior synechiae, and worsen ciliary spasm pain. * **Beta-blockers (C):** These are used to reduce intraocular pressure in glaucoma by decreasing aqueous humor production. They have no anti-inflammatory effect and do not treat the underlying uveitis. * **NSAIDs (D):** While they have anti-inflammatory properties, they are generally insufficient as a primary treatment for the intense intraocular inflammation seen in pars planitis. They may occasionally be used as an adjunct for CME. **High-Yield Clinical Pearls for NEET-PG:** * **Snowbanking:** Pathognomonic feature found at the inferior pars plana. * **Complications:** Cystoid Macular Edema (CME) is the most common; complicated cataract and vitreous hemorrhage can also occur. * **Treatment Ladder:** If steroids fail or are contraindicated, the next steps include **Cryotherapy**, **Laser photocoagulation**, or **Immunosuppressants** (e.g., Methotrexate, Cyclosporine).

Question 40: Which is the shortest acting mydriatic?

A. Tropicamide (Correct Answer)
B. Atropine
C. Phenylephrine
D. Hyoscine

Explanation: **Explanation:** The duration of action of mydriatics (drugs that dilate the pupil) is a high-yield topic in NEET-PG, as it dictates their clinical utility in diagnosis versus treatment. **1. Why Tropicamide is correct:** Tropicamide is a synthetic antimuscarinic drug with the **fastest onset (15–30 minutes)** and the **shortest duration of action (4–6 hours)**. This makes it the drug of choice for diagnostic procedures like fundus examination, where rapid dilation is needed and the patient requires a quick recovery of vision (accommodation) to resume daily activities. **2. Analysis of Incorrect Options:** * **Atropine:** This is the **longest-acting** mydriatic and cycloplegic. Its effects can last for **7–12 days**. It is never used for routine diagnostic dilation but is used for treating uveitis or performing refraction in children with high accommodative reserve. * **Hyoscine (Scopolamine):** An intermediate-acting antimuscarinic. Its effects last for **3–7 days**. * **Phenylephrine:** This is a sympathomimetic (alpha-1 agonist). While it has a relatively short duration (3–6 hours), it is a **pure mydriatic** (no cycloplegia). In the context of "shortest acting" among standard clinical mydriatics, Tropicamide is the classic pharmacological answer due to its rapid offset of both mydriasis and cycloplegia. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mydriatic of choice for Fundoscopy:** Tropicamide (0.5% or 1%). * **Mydriatic of choice for Children (<5 years):** Atropine (due to strong ciliary muscle tone). * **Mydriatic of choice for School-aged children:** Cyclopentolate (Duration: 24 hours). * **Side Effect Note:** Always rule out narrow-angle glaucoma before instilling mydriatics, as they can precipitate an acute attack. * **Order of duration (Shortest to Longest):** Tropicamide < Phenylephrine < Cyclopentolate < Homatropine < Hyoscine < Atropine.

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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