Ophthalmic Pharmacology Practice Questions

Q: Which of the following medications increases aqueous humor outflow?

Latanoprost. **Explanation:** The management of intraocular pressure (IOP) involves either decreasing aqueous humor production or increasing its drainage (outflow). **Correct Answer: B. Latanoprost** Latanoprost is a **Prostaglandin F2α analog**. It is the drug of choice for Primary Open Angle Glaucoma (POAG) because it significantly increases aqueous drainage via the **Uveoscleral pathway** (the unconventional route). It works by remodeling the extracellular matrix in the ciliary muscle, reducing resistance to flow. **Incorrect Options:** * **A. Timolol:** A non-selective **Beta-blocker**. It reduces IOP by **decreasing the production** of aqueous humor from the ciliary body epithelium. It does not affect outflow. * **C. Atropine:** An **Anticholinergic (Mydriatic)**. It can actually decrease outflow by causing mydriasis, which may crowd the angle and precipitate acute angle-closure glaucoma in predisposed eyes. * **D. Dorzolamide:** A topical **Carbonic Anhydrase Inhibitor**. Like beta-blockers, it works by **decreasing the secretion** of aqueous humor by inhibiting the enzyme necessary for bicarbonate production in the ciliary processes. **High-Yield Clinical Pearls for NEET-PG:** * **Uveoscleral Outflow:** Increased by Prostaglandins (Latanoprost, Bimatoprost) and Alpha-agonists (Apraclonidine, Brimonidine). * **Trabecular Outflow:** Increased by Miotics (Pilocarpine) by contracting the ciliary muscle and opening the trabecular meshwork. * **Side Effects of Latanoprost:** Increased iris pigmentation (heterochromia), hypertrichosis (thickening of eyelashes), and cystoid macular edema (CME). * **Contraindication:** Avoid Beta-blockers (Timolol) in patients with Asthma or Heart Block.

Q: What is the primary mechanism by which carbonic anhydrase inhibitors reduce intraocular pressure (IOP)?

Decrease aqueous humor production. ### Explanation **Primary Mechanism: Decrease Aqueous Humor Production** Carbonic anhydrase inhibitors (CAIs), such as Acetazolamide (oral) and Dorzolamide (topical), work by inhibiting the enzyme **carbonic anhydrase II** located in the non-pigmented ciliary epithelium. Under normal conditions, this enzyme facilitates the reaction: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$ The bicarbonate ($HCO_3^-$) ions are essential for the active transport of sodium and water into the posterior chamber. By inhibiting this enzyme, CAIs reduce the availability of bicarbonate ions, leading to a significant decrease (up to 40-60%) in the active secretion of aqueous humor, thereby lowering IOP. **Analysis of Incorrect Options:** * **Option A (Uveoscleral Outflow):** This is the primary mechanism for **Prostaglandin analogues** (e.g., Latanoprost). * **Option B (Trabecular Outflow):** This is the primary mechanism for **Miotics** (e.g., Pilocarpine) and Rho-kinase inhibitors. * **Option D:** Incorrect, as CAIs have no significant effect on the outflow pathways. **High-Yield Clinical Pearls for NEET-PG:** * **Systemic Side Effects (Acetazolamide):** Paresthesia (most common), metabolic acidosis, hypokalemia, and renal stones. * **Contraindications:** Avoid in patients with **Sulfa allergy**, severe renal/hepatic impairment, and COPD (due to acidosis). * **Topical CAIs:** Dorzolamide and Brinzolamide are preferred for chronic management to avoid systemic side effects, though they may cause a bitter taste (dysgeusia). * **Drug of Choice:** Acetazolamide is the drug of choice for rapid IOP reduction in **Acute Angle Closure Glaucoma**.

Q: Color blindness is caused by which of the following?

Ethambutol. **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).

Q: What is Ozurdex?

0.7 mg dexamethasone. **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.

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

Atropine sulphate eye ointment. 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).

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

Adrenergic agonist. **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.

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

Prostaglandin analogues. **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.

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

Glaucoma. **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.

Q: Which drug is known to cause cataracts?

Dexamethasone. **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 1

What is the drug of choice for anterior uveitis?

Accepted Answer

Topical steroids

Answer

Oral steroids

Answer

Topical antibiotics

Answer

Atropine

Question 2

Which of the following medications increases aqueous humor outflow?

Accepted Answer

Latanoprost

Answer

Timolol

Answer

Atropine

Answer

Dorzolamide

Question 3

What is the primary mechanism by which carbonic anhydrase inhibitors reduce intraocular pressure (IOP)?

Accepted Answer

Decrease aqueous humor production

Answer

Increase uveoscleral outflow

Answer

Increase trabecular meshwork outflow

Answer

All of the above

Question 4

Color blindness is caused by which of the following?

Accepted Answer

Ethambutol

Answer

Chloroquine

Answer

Digitalis

Answer

Pyrazinamide

Question 5

What is Ozurdex?

Accepted Answer

0.7 mg dexamethasone

Answer

0.5 mg triamcinolone

Answer

0.6 mg betamethasone

Answer

0.7 mg Triamcinolone

Question 6

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

Accepted Answer

Atropine sulphate eye ointment

Answer

Dexamethasone eye drops

Answer

Pilocarpine eye drops

Answer

Lignocaine eye drops

Question 7

Conjunctival adrenochrome is a side effect of which class of drugs?

Accepted Answer

Adrenergic agonist

Answer

Carbonic anhydrase inhibitor

Answer

PG analogue

Answer

Parasympathomimetic

Question 8

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

Accepted Answer

Prostaglandin analogues

Answer

Alpha agonist

Answer

Acetazolamide

Answer

Beta blockers

Question 9

Topical steroids are associated with which of the following conditions?

Accepted Answer

Glaucoma

Answer

Post subcapsular cataract

Answer

Uveitis

Answer

Ptosis

Question 10

Which drug is known to cause cataracts?

Accepted Answer

Dexamethasone

Answer

Amikacin

Answer

Chloramphenicol

Answer

Penicillin

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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