Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology Indian Medical PG Practice Questions and MCQs

Question 141: Color blindness is caused by which of the following?

A. Chloroquine
B. Ethambutol (Correct Answer)
C. Digitalis
D. Pyrazinamide

Explanation: **Explanation:** **Ethambutol** is a well-known cause of **toxic optic neuropathy**. It is dose-dependent and duration-dependent, typically occurring when doses exceed 15 mg/kg/day. The drug chelates copper, interfering with mitochondrial enzymes in the optic nerve. The earliest clinical sign of ethambutol toxicity is a **loss of color vision (specifically red-green dyschromatopsia)**, followed by a reduction in visual acuity and the development of a **centrocecal scotoma**. Because these changes can be reversible if caught early, patients on Ethambutol require baseline and monthly ophthalmic monitoring. **Analysis of Incorrect Options:** * **Chloroquine:** Primarily causes **"Bull’s Eye Maculopathy"** due to its affinity for melanin in the Retinal Pigment Epithelium (RPE). While it affects central vision and field of vision in advanced stages, it is not the classic answer for drug-induced color blindness in the context of anti-tubercular therapy. * **Digitalis:** Toxicity typically causes **Xanthopsia** (yellowish-green tint to vision) and "snowy" vision or halos, rather than a true red-green color deficiency. * **Pyrazinamide:** This is an anti-tubercular drug that is not associated with significant ocular toxicity; its primary side effects are hepatotoxicity and hyperuricemia. **NEET-PG High-Yield Pearls:** * **Ethambutol Toxicity:** Early signs are **Red-Green color blindness** and decreased **Contrast Sensitivity**. * **Screening:** Use **Ishihara Charts** for color vision and **Snellen’s Chart** for acuity. * **Reversibility:** Toxicity is usually reversible upon immediate discontinuation of the drug. * **Other drugs causing color vision changes:** Sildenafil (Cyanopsia/Blue vision) and Digitalis (Xanthopsia/Yellow vision).

Question 142: Which drug is contraindicated in uveitis?

A. Pilocarpine (Correct Answer)
B. Acetazolamide
C. Atropine
D. Steroids

Explanation: **Explanation:** In the management of uveitis, the primary goals are to reduce inflammation, relieve pain, and prevent the formation of **synechiae** (adhesions between the iris and the lens). **Why Pilocarpine is Contraindicated:** Pilocarpine is a **miotic** (parasympathomimetic). It is strictly contraindicated in uveitis for three main reasons: 1. **Synechiae Formation:** By constricting the pupil, it increases the surface area of contact between the posterior iris and the anterior lens capsule, promoting **posterior synechiae**. 2. **Blood-Aqueous Barrier:** It causes vasodilation and increases capillary permeability, which further breaks down the blood-aqueous barrier, worsening the inflammatory exudation. 3. **Pain:** It induces ciliary muscle contraction (ciliary spasm), significantly increasing the patient's pain. **Analysis of Incorrect Options:** * **Atropine (Option C):** This is the **drug of choice** for uveitis. As a potent cycloplegic and mydriatic, it puts the ciliary body at rest (relieving pain) and keeps the pupil dilated to prevent or break synechiae. * **Steroids (Option D):** These are the mainstay of treatment to suppress the inflammatory response and prevent tissue damage. * **Acetazolamide (Option B):** This carbonic anhydrase inhibitor is used to manage secondary glaucoma, a common complication of uveitis. **High-Yield NEET-PG Pearls:** * **Mydriatic of choice in Uveitis:** Atropine 1% (Longest acting). * **Triple Action of Atropine in Uveitis:** 1. Ciliary rest (decreases pain), 2. Prevents synechiae, 3. Reduces exudation by decongesting iris vessels. * **Festooned Pupil:** An irregular pupil shape seen in uveitis due to segmental posterior synechiae, often visualized better after instilling a mydriatic.

Question 143: What is Ozurdex?

A. 0.5 mg triamcinolone
B. 0.7 mg dexamethasone (Correct Answer)
C. 0.6 mg betamethasone
D. 0.7 mg Triamcinolone

Explanation: **Explanation:** **Ozurdex** is a biodegradable, sustained-release intravitreal implant containing **0.7 mg of dexamethasone**. It is composed of a polyglactic acid-polyglycolic acid (PLGA) polymer matrix that slowly degrades into lactic acid and glycolic acid, allowing for the controlled release of the steroid into the vitreous cavity for up to 6 months. * **Why Option B is Correct:** Ozurdex is specifically formulated with 0.7 mg of dexamethasone. It is FDA-approved for the treatment of macular edema following Branch Retinal Vein Occlusion (BRVO) or Central Retinal Vein Occlusion (CRVO), non-infectious posterior uveitis, and diabetic macular edema (DME). * **Why Options A, C, and D are Incorrect:** While Triamcinolone acetonide is frequently used intravitreally (e.g., **Triesence** or **Kenalog-40**), it is not the active ingredient in the Ozurdex implant. Similarly, Betamethasone is not used in this specific sustained-release delivery system. The dosage of 0.7 mg is unique to the Dexamethasone delivery profile of Ozurdex. **High-Yield Clinical Pearls for NEET-PG:** 1. **Mechanism:** It is a potent anti-inflammatory that inhibits phospholipase A2, thereby reducing edema, fibrin deposition, and capillary leakage. 2. **Delivery:** It is injected via a 22-gauge applicator through the pars plana. 3. **Side Effects:** The most common "steroid-induced" complications are **cataract formation** (most common) and **increased intraocular pressure (IOP)**. 4. **Advantage:** Unlike Triamcinolone, Ozurdex is biodegradable and does not require surgical removal.

Question 144: Which of the following will be the most important adjuvant therapy in a case of fungal corneal ulcer?

A. Atropine sulphate eye ointment (Correct Answer)
B. Dexamethasone eye drops
C. Pilocarpine eye drops
D. Lignocaine eye drops

Explanation: In cases of fungal corneal ulcers, **Atropine sulphate (1%) eye ointment** is the most important adjuvant therapy alongside antifungal agents. ### Why Atropine is the Correct Choice Corneal ulcers, whether bacterial or fungal, are almost always associated with **secondary anterior uveitis** (iridocyclitis). This occurs because toxins from the ulcer diffuse into the anterior chamber, causing ciliary body irritation. * **Relief of Ciliary Spasm:** Atropine is a potent cycloplegic that relaxes the ciliary muscle, significantly reducing ocular pain. * **Prevention of Synechiae:** As a strong mydriatic, it keeps the pupil dilated, preventing the formation of posterior synechiae (adhesion of the iris to the lens). * **Improved Blood Flow:** By reducing ciliary congestion, it may improve ocular circulation, aiding the healing process. ### Why Other Options are Incorrect * **B. Dexamethasone:** Steroids are generally **contraindicated** in active fungal ulcers. They suppress the local immune response and promote fungal replication, often leading to corneal perforation. * **C. Pilocarpine:** This is a miotic. It would worsen the pain by causing ciliary muscle contraction and increase the risk of pupillary block and synechiae formation. * **D. Lignocaine:** Topical anesthetics are never used as therapy. They are toxic to the corneal epithelium and can mask worsening symptoms, leading to "corneal melting." ### High-Yield Clinical Pearls for NEET-PG * **Drug of Choice (DOC) for Fungal Ulcer:** Topical **Natamycin (5%)** is the first-line treatment for filamentous fungi (e.g., *Aspergillus, Fusarium*). * **Atropine vs. Homatropine:** While Atropine is preferred for its long-lasting effect, Homatropine may be used in milder cases. * **The "Steroid Rule":** Never use steroids in a corneal ulcer unless the infection is controlled and the ulcer is viral (specifically Disciform Keratitis).

Question 145: Conjunctival adrenochrome is a side effect of which class of drugs?

A. Adrenergic agonist (Correct Answer)
B. Carbonic anhydrase inhibitor
C. PG analogue
D. Parasympathomimetic

Explanation: **Explanation:** **Adrenochrome deposits** are a classic side effect associated with the chronic use of **Adrenergic agonists**, specifically topical **Epinephrine** (and its prodrug Dipivefrin). These drugs are historically used in glaucoma management. Adrenochrome is a pigmented oxidation product of epinephrine. When the drug is instilled, it can undergo oxidative polymerization, leading to the formation of small, discrete, dark brown or black melanin-like deposits. These are typically found in the palpebral conjunctiva or within conjunctival cysts. **Analysis of Incorrect Options:** * **Carbonic Anhydrase Inhibitors (e.g., Dorzolamide):** These primarily cause local irritation, a bitter taste (dysgeusia), and rarely, punctate keratitis, but do not cause pigment deposition. * **PG Analogues (e.g., Latanoprost):** While these cause pigmentation, it occurs in the **iris** (permanent) and the **eyelash follicles** (trichomegaly and hypertrichosis), not as conjunctival adrenochrome deposits. * **Parasympathomimetics (e.g., Pilocarpine):** These are associated with miosis, accommodative spasm (brow ache), and long-term risks of retinal detachment or iris cysts, but not pigment oxidation. **Clinical Pearls for NEET-PG:** * **Triad of Epinephrine side effects:** Conjunctival adrenochrome, pupillary mydriasis, and Cystoid Macular Edema (CME) in aphakic patients. * **Differential Diagnosis:** Adrenochrome deposits can be mistaken for foreign bodies or conjunctival nevi. * **Key Association:** If a question mentions "black spots on the conjunctiva" in a glaucoma patient on old-school drops, think Adrenochrome.

Question 146: What is the single drug used for the treatment of trachoma?

A. Tetracycline
B. Doxycycline
C. Azithromycin (Correct Answer)
D. Chloramphenicol

Explanation: **Explanation:** The correct answer is **Azithromycin**. Trachoma, caused by *Chlamydia trachomatis* (serotypes A, B, Ba, and C), is the leading infectious cause of blindness worldwide. **Why Azithromycin is the drug of choice:** Under the WHO-recommended **SAFE strategy** (Surgery, Antibiotics, Facial cleanliness, Environmental improvement), a **single oral dose of Azithromycin (20 mg/kg up to 1 g)** is the gold standard for mass drug administration. Its superiority lies in its long tissue half-life, excellent intracellular penetration, and high patient compliance compared to multi-dose regimens. **Analysis of Incorrect Options:** * **Tetracycline (A):** While effective, it must be applied topically as a 1% ointment twice daily for 6 weeks. This leads to poor compliance and is less effective for mass treatment. * **Doxycycline (B):** This is a second-line oral alternative to Azithromycin but requires a 10-14 day course, making it unsuitable as a "single drug" treatment for community control. * **Chloramphenicol (D):** This is a broad-spectrum antibiotic but is not the drug of choice for Chlamydial infections and carries risks of bone marrow toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **SAFE Strategy:** Remember the acronym for Trachoma control. * **WHO Grading (FISTO):** **F**ollicular, **I**ntense inflammation, **S**carring, **T**richiasis, **O**pacity. * **Arlt’s Line:** Horizontal scarring in the upper palpebral conjunctiva. * **Herbert’s Pits:** Scarred limbal follicles (pathognomonic). * **Drug of choice in pregnancy/children:** Azithromycin remains the preferred choice (Tetracyclines are contraindicated).

Question 147: "Bull's Eye" lesion in the retina is seen in toxicity with any of the following drugs?

A. Ethambutol
B. Digitalis
C. Chloroquine (Correct Answer)
D. Rifampicin

Explanation: **Explanation:** **Bull’s Eye Maculopathy** is a classic clinical finding characterized by a central area of hyperpigmentation surrounded by a zone of depigmentation (atrophy of the Retinal Pigment Epithelium), which is further encircled by a ring of hyperpigmentation. **1. Why Chloroquine is correct:** Chloroquine and its derivative, **Hydroxychloroquine**, have a high affinity for melanin-rich tissues like the Retinal Pigment Epithelium (RPE). The drug binds to melanin, leading to chronic accumulation and subsequent RPE atrophy and photoreceptor loss. This results in the characteristic "Bull’s Eye" appearance on fundoscopy. Early toxicity is often detected using **10-2 Visual Fields** or **Spectral Domain OCT**, as the damage is irreversible once the Bull's Eye lesion is visible. **2. Why other options are incorrect:** * **Ethambutol:** Primarily causes **Optic Neuritis** (retrobulbar). It typically presents with decreased visual acuity and red-green color blindness, not a macular lesion. * **Digitalis:** Causes **Xanthopsia** (yellow-tinted vision) and snowy vision due to its effect on cone cells, but it does not cause structural macular lesions. * **Rifampicin:** Known for causing orange-red discoloration of body fluids (tears, urine) but is not associated with retinal toxicity. **Clinical Pearls for NEET-PG:** * **Other causes of Bull’s Eye Maculopathy:** Stargardt’s disease, Cone-Dystrophy, Benign Concentric Macular Dystrophy, and Chronic Macular Hole. * **Screening:** The American Academy of Ophthalmology recommends a baseline eye exam followed by annual screening after 5 years of use (or earlier if high-risk factors like renal disease or high dosage exist). * **Safe Dose:** <5.0 mg/kg real weight for Hydroxychloroquine.

Question 148: A patient presents with diabetic macular edema and glaucoma. Which of the following drugs should be avoided for this patient?

A. Alpha agonist
B. Acetazolamide
C. Beta blockers
D. Prostaglandin analogues (Correct Answer)

Explanation: **Explanation:** The correct answer is **Prostaglandin analogues (PGAs)**. **Why Prostaglandin Analogues are avoided:** Prostaglandin analogues (e.g., Latanoprost, Bimatoprost) are potent ocular hypotensive agents, but they are known to increase the levels of endogenous inflammatory mediators. In patients with pre-existing blood-retinal barrier breakdown—such as those with **Diabetic Macular Edema (DME)**, uveitis, or aphakia—PGAs can exacerbate or induce **Cystoid Macular Edema (CME)**. Therefore, they are generally avoided or used with extreme caution in patients with active macular pathology. **Analysis of Incorrect Options:** * **Alpha agonists (e.g., Brimonidine):** These are generally safe in DME. Interestingly, Brimonidine is being studied for potential neuroprotective effects on the retina. * **Acetazolamide:** This is a Carbonic Anhydrase Inhibitor (CAI). Systemic CAIs are actually sometimes used to *treat* macular edema (especially in Retinitis Pigmentosa) because they help pump fluid out of the subretinal space. * **Beta blockers (e.g., Timolol):** These are standard first-line treatments for glaucoma and have no known adverse effect on macular edema or diabetic retinopathy. **NEET-PG High-Yield Pearls:** * **Drug of Choice for DME:** Intravitreal Anti-VEGF (e.g., Ranibizumab, Aflibercept) is the gold standard. * **PGA Side Effects:** Increased iris pigmentation, hypertrichosis (eyelash growth), deepening of the sulcus, and reactivation of Herpes Simplex Keratitis. * **Glaucoma Drug to avoid in Asthma/Heart Block:** Beta blockers. * **Glaucoma Drug to avoid in Sulfa Allergy:** Carbonic Anhydrase Inhibitors.

Question 149: Topical steroids are associated with which of the following conditions?

A. Post subcapsular cataract
B. Glaucoma (Correct Answer)
C. Uveitis
D. Ptosis

Explanation: **Explanation:** The correct answer is **Glaucoma**. Topical steroids are a well-known cause of secondary open-angle glaucoma, often referred to as **"Steroid-Induced Glaucoma."** **Mechanism:** Steroids increase the resistance to aqueous outflow by causing structural changes in the trabecular meshwork. They induce the expression of **myocilin** (TIGR gene) and increase the deposition of glycosaminoglycans (GAGs) in the trabecular meshwork, leading to decreased pore size and reduced drainage. **Analysis of Options:** * **A. Posterior Subcapsular Cataract (PSC):** While steroids *do* cause PSC, it is primarily associated with **systemic** steroid use or very long-term topical use. In the context of "Topical Steroids" as a classic side effect profile in exams, Glaucoma is the more immediate and characteristic local ocular hypertensive response. (Note: If this were a "Multiple Correct" type question, PSC would also be right, but Glaucoma is the primary pharmacological association for topical administration). * **C. Uveitis:** Steroids are actually the **treatment** for uveitis, not the cause. They reduce intraocular inflammation. * **D. Ptosis:** Steroids do not typically cause ptosis. However, long-term use of steroid drops containing preservatives may rarely cause ocular surface toxicity, but it is not a classic association. **High-Yield Clinical Pearls for NEET-PG:** * **Steroid Responders:** About 5–10% of the general population are "High Responders" who show a significant rise in IOP (>15 mmHg) after 4 weeks of topical steroids. * **Potency:** Dexamethasone and Prednisolone have a higher risk of inducing glaucoma compared to "soft steroids" like **Loteprednol** or **Fluorometholone**. * **Contraindication:** Topical steroids are strictly contraindicated in **Herpes Simplex Keratitis (Dendritic ulcer)** as they can lead to geographic ulcers and corneal perforation.

Question 150: Which of the following statements about toxic amblyopia is FALSE?

A. Tobacco-alcohol amblyopia is characterized by foggy vision associated with bilateral centrocecal scotomas.
B. Methyl alcohol amblyopia results from degeneration of ganglion cells of the retina.
C. Quinine amblyopia: Visual loss may be associated with deafness and tinnitus.
D. Ethambutol amblyopia progresses even after cessation of the drug. (Correct Answer)

Explanation: **Explanation:** **Why Option D is the Correct (False) Statement:** Ethambutol-induced optic neuropathy is typically **reversible** if the drug is discontinued promptly at the onset of symptoms. The underlying mechanism involves the chelation of copper and zinc, interfering with mitochondrial function in the optic nerve. Once the drug is stopped, the toxic insult ceases, and vision usually improves or stabilizes over 3–6 months. It does **not** characteristically progress after cessation, unlike certain other neurotoxicities. **Analysis of Other Options:** * **Option A (Tobacco-alcohol amblyopia):** This is a nutritional deficiency (Vitamin B12/Folate) exacerbated by toxins. It classically presents with **bilateral, symmetrical centrocecal scotomas** (defects extending from the fixation point to the blind spot) and blurred/foggy vision. * **Option B (Methyl alcohol amblyopia):** Methanol is metabolized into **formic acid**, which is highly toxic to the retina. It causes profound **degeneration of retinal ganglion cells** and the optic nerve, often leading to permanent blindness and "snowfield" vision. * **Option C (Quinine amblyopia):** Quinine toxicity (Cinchonism) presents with a triad of **visual loss** (marked peripheral field constriction), **tinnitus**, and **deafness**. The fundus may initially appear normal but later shows "cherry red spot" or optic atrophy. **High-Yield Clinical Pearls for NEET-PG:** * **Ethambutol Monitoring:** Patients should undergo baseline and monthly screening for visual acuity, color vision (red-green), and visual fields. * **Dose-Dependency:** Ethambutol toxicity is rare at 15 mg/kg but increases significantly at doses >25 mg/kg. * **Amiodarone:** Another high-yield drug causing optic neuropathy; it presents with insidious, bilateral disc swelling. * **Centrocecal Scotoma:** The hallmark of toxic and nutritional optic neuropathies.

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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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