Ophthalmic Pharmacology Practice Questions

Q: What is the topically used non-selective alpha-agonist in glaucoma?

Dipivefrine. **Explanation:** **Dipivefrine** is the correct answer because it is a prodrug of **Epinephrine**, which is a **non-selective alpha and beta-adrenergic agonist**. **Mechanism of Action:** Dipivefrine is converted into epinephrine by esterases in the cornea. It lowers intraocular pressure (IOP) through a dual mechanism: 1. **Initial effect:** Increases aqueous outflow through the trabecular meshwork (alpha-1 effect). 2. **Secondary effect:** Decreases aqueous production (alpha-2 effect) and increases uveoscleral outflow. As a prodrug, it is more lipophilic than epinephrine, allowing for better corneal penetration and fewer systemic side effects. **Analysis of Incorrect Options:** * **A. Bimatoprost:** This is a **Prostamide (Prostaglandin analogue)**. It is currently the first-line treatment for glaucoma and works by increasing uveoscleral outflow. * **B. Dorzolamide:** This is a topical **Carbonic Anhydrase Inhibitor (CAI)**. It reduces IOP by decreasing the production of aqueous humor from the ciliary body epithelia. * **C. Brimonidine:** While an alpha-agonist, it is **highly selective for Alpha-2 receptors**. It is not non-selective. It reduces aqueous production and increases uveoscleral outflow. **High-Yield Clinical Pearls for NEET-PG:** * **Adrenochrome deposits:** Epinephrine/Dipivefrine can cause black pigment deposits in the conjunctiva. * **Cystoid Macular Edema (CME):** Epinephrine compounds are contraindicated in **aphakic** patients as they can induce CME. * **Mydriasis:** Unlike Brimonidine, Dipivefrine can cause pupillary dilation; hence, it is contraindicated in angle-closure glaucoma. * **Drug of choice (DOC)** for primary open-angle glaucoma (POAG) is Prostaglandin analogues (e.g., Latanoprost).

Q: Steroids are contraindicated in which of the following conditions?

Dendritic ulcer. **Explanation:** The correct answer is **Dendritic ulcer**, which is the hallmark of **Herpes Simplex Keratitis (HSK)**. **1. Why Dendritic Ulcer is the Correct Answer:** A dendritic ulcer is caused by active viral replication of the Herpes Simplex Virus (HSV) in the corneal epithelium. **Steroids are strictly contraindicated** during the active epithelial stage because they inhibit the local immune response and promote viral replication. This can lead to the expansion of the ulcer into a large, geographic ulcer and may result in corneal perforation. Steroids also increase the risk of secondary fungal infections and steroid-induced glaucoma. **2. Analysis of Incorrect Options:** * **Phlyctenular conjunctivitis:** This is a delayed hypersensitivity reaction (Type IV) to endogenous antigens (like Tubercular protein). Topical steroids are the **treatment of choice** to suppress this allergic response. * **Granular conjunctivitis (Trachoma):** While primarily treated with antibiotics (Azithromycin), steroids are not contraindicated; they may occasionally be used to manage symptomatic follicular inflammation. * **Mooren's ulcer:** This is an idiopathic, peripheral ulcerative keratitis of autoimmune origin. Topical and systemic **steroids are a mainstay of treatment** to halt the progressive destruction of the corneal stroma. **3. NEET-PG High-Yield Pearls:** * **The "Steroid Exception" in HSK:** While contraindicated in *epithelial* (dendritic) keratitis, steroids are the treatment of choice for *stromal* (disciform) keratitis, provided they are covered by prophylactic antiviral drops. * **Rose Bengal Stain:** This stain is specific for the "devitalized cells" at the base and margins of a dendritic ulcer. * **Side Effects of Long-term Steroids:** Always remember the "Two C's"—**C**ataract (Posterior Subcapsular) and **C**upping (Glaucoma).

Q: Bull's eye lesion in the macula is seen with which of the following medications?

Chloroquine. **Explanation:** **Chloroquine (and Hydroxychloroquine)** are the classic causes of **Bull’s eye maculopathy**. These drugs have a high affinity for melanin and accumulate in the **Retinal Pigment Epithelium (RPE)**. The toxicity manifests as a central area of RPE atrophy (pale) surrounded by a ring of spared RPE, which is further encircled by another ring of atrophy, giving the characteristic "Bull's eye" appearance on fundoscopy. This leads to progressive, irreversible visual field loss (scotomas). **Analysis of Incorrect Options:** * **Primaquine:** An antimalarial used for radical cure (liver stages); it is primarily associated with hematologic side effects like hemolysis in G6PD deficiency, not retinal toxicity. * **Quinine:** Known for causing **"Quinine Amblyopia."** Acute toxicity leads to sudden vision loss, pupillary abnormalities, and marked arteriolar narrowing (cherry red spot may be seen), but not a Bull's eye lesion. * **Sulfamethoxazole:** A sulfonamide that can cause hypersensitivity reactions (Stevens-Johnson Syndrome) or acute transient myopia/angle-closure glaucoma due to ciliary body edema, but it is not associated with macular pigmentary changes. **High-Yield Clinical Pearls for NEET-PG:** * **Other causes of Bull’s eye maculopathy:** Stargardt’s disease (most common genetic cause), Cone dystrophy, and Chronic Thioridazine toxicity. * **Screening:** The most sensitive tests for early detection are **Automated Visual Fields (10-2)** and **Spectral Domain OCT (SD-OCT)**, which shows the "Flying Saucer" sign (loss of outer retinal layers). * **Dosage:** Toxicity risk increases significantly when the daily dose of Hydroxychloroquine exceeds **5 mg/kg** of real body weight.

Q: Latanoprost is a relatively newer agent. Which of the following statements is true regarding this agent?

It is a PGF2a derivative used in glaucoma.. **Explanation:** **Latanoprost** is a high-yield topic in Ophthalmic Pharmacology. It is a **Prostaglandin F2α (PGF2α) analogue** that acts as a selective agonist at the FP receptor. It is primarily used as a first-line treatment for **Open-Angle Glaucoma (OAG)** and Ocular Hypertension. Its mechanism of action involves increasing the **uveoscleral outflow** of aqueous humor, thereby reducing intraocular pressure (IOP). **Analysis of Options:** * **Option A (Correct):** Latanoprost is indeed a PGF2α derivative. Unlike traditional drugs (like Beta-blockers) that decrease aqueous production, Latanoprost enhances the drainage through the unconventional uveoscleral pathway. * **Option B (Incorrect):** Selective α1 blockers (e.g., Tamsulosin, Alfuzosin) are used for BPH, but Latanoprost has no action on adrenergic receptors. * **Option C (Incorrect):** 5α-reductase inhibitors (e.g., Finasteride, Dutasteride) prevent the conversion of testosterone to DHT. Latanoprost is not a hormonal modulator. * **Option D (Incorrect):** PGE2 analogues used for cervical priming/induction of labor include **Dinoprostone**. While Latanoprost is a prostaglandin, its specific PGF2α structure and formulation are dedicated to ophthalmic use. **High-Yield Clinical Pearls for NEET-PG:** 1. **Side Effects:** The most characteristic side effects are **increased iris pigmentation** (permanent browning), **hypertrichosis** (increased eyelash growth/thickness), and **prostaglandin-associated periorbitopathy**. 2. **Dosing:** It is administered as **once-daily** eye drops (usually at night), which ensures better patient compliance compared to multi-dose regimens. 3. **Contraindication:** It should be avoided in patients with active **uveitis** or **cystoid macular edema (CME)** as it may exacerbate inflammation.

Q: Topical Pilocarpine 1% administration failed to produce pupillary constriction in a patient with a large dilated pupil. What is the most probable reason for this failure?

Pharmacological blockade. **Explanation:** The clinical scenario describes a **Pilocarpine Challenge Test**, used to differentiate the causes of a fixed, dilated pupil (mydriasis). **1. Why Pharmacological Blockade is correct:** Pilocarpine is a direct-acting parasympathomimetic (cholinergic agonist) that acts directly on the muscarinic receptors of the iris sphincter muscle. In cases of **pharmacological blockade** (accidental or intentional instillation of atropine, tropicamide, or scopolamine), the muscarinic receptors are physically occupied and blocked. Therefore, even a 1% or 2% concentration of Pilocarpine cannot bind to the receptors, and the pupil fails to constrict. **2. Why other options are incorrect:** * **Adie’s Tonic Pupil:** This is due to post-ganglionic denervation of the ciliary ganglion. The iris sphincter becomes hypersensitive to cholinergic drugs (**Denervation Supersensitivity**). It will constrict even with very dilute Pilocarpine (0.125%), which would not affect a normal pupil. * **Uncal Herniation & Diabetic III Nerve Palsy:** Both involve damage to the IIIrd cranial nerve (pre-ganglionic). Since the iris sphincter muscle and its receptors remain intact and healthy, they will respond normally and **constrict** when 1% Pilocarpine is applied directly to the eye. **Clinical Pearls for NEET-PG:** * **The 1% Pilocarpine Test:** If the pupil constricts, the cause is neurological (III Nerve palsy). If it fails to constrict, the cause is pharmacological (atropine-like drugs) or structural (iris ischemia/trauma). * **Adie’s Pupil Diagnosis:** Use **0.125% Pilocarpine**. Constriction = Adie’s; No constriction = Normal pupil. * **Apraclonidine Test:** Used for Horner’s Syndrome (causes reversal of anisocoria).

Q: Which is the fastest acting cycloplegic drug?

Tropicamide. **Explanation:** The speed of onset of a cycloplegic drug is determined by its pharmacokinetics and its affinity for the muscarinic receptors in the ciliary muscle. **1. Why Tropicamide is correct:** Tropicamide is a synthetic derivative of tropic acid with the **fastest onset of action** among all cycloplegics and mydriatics. It reaches its peak mydriatic effect in 20–40 minutes and peak cycloplegic effect within **20–30 minutes**. Due to its rapid onset and short duration of action (4–6 hours), it is the drug of choice for routine fundus examinations. **2. Analysis of Incorrect Options:** * **Atropine (A):** It is the most potent cycloplegic but has the **slowest onset** (30–60 minutes for peak effect) and the longest duration (7–12 days). It is used primarily for refraction in children under 7 years or in cases of active uveitis. * **Cyclopentolate (C):** It has a rapid onset (25–75 minutes) and is the **drug of choice for cycloplegic refraction** in children and young adults, but it is slower than Tropicamide. * **Homatropine (D):** This is a semi-synthetic alkaloid with an intermediate onset (30–60 minutes) and duration (1–3 days). It is less potent than Atropine and is mainly used in the treatment of anterior uveitis to prevent synechiae. **High-Yield Clinical Pearls for NEET-PG:** * **Fastest Acting:** Tropicamide. * **Most Potent/Longest Acting:** Atropine. * **Drug of Choice (DOC) for Cycloplegic Refraction (Children):** Cyclopentolate. * **DOC for Refraction in Children <7 years/Accommodative Esotropia:** Atropine (Ointment is preferred over drops to prevent systemic toxicity). * **Mechanism:** All these drugs are **parasympatholytics** (Muscarinic antagonists) that block the M3 receptors in the sphincter pupillae (causing mydriasis) and the ciliary muscle (causing cycloplegia).

Q: Which of the following is true regarding the ophthalmic use of topical retinoic acid?

Ocular-surface squamous neoplasm. **Explanation** The correct answer is **C. Ocular-surface squamous neoplasm (OSSN)**. **Why it is correct:** Retinoids (Vitamin A derivatives) play a critical role in regulating the growth and differentiation of epithelial cells. In the context of **Ocular-surface squamous neoplasm (OSSN)**, topical retinoic acid (specifically All-trans retinoic acid or ATRA) acts by inducing cell cycle arrest and promoting the redifferentiation of neoplastic squamous cells back into normal epithelium. It is often used as an adjunctive or alternative therapy to surgical excision, or in combination with other topical chemotherapeutic agents like Mitomycin-C, 5-Fluorouracil, or Interferon alpha-2b. **Why other options are incorrect:** * **A & B (Conjunctival melanoma / Naevus):** These are melanocytic tumors (derived from melanocytes). Retinoic acid targets epithelial differentiation and is not an effective treatment for pigmented or melanocytic lesions. * **D (Pterygium):** While pterygium involves epithelial proliferation, the primary treatment is surgical excision (with autograft). Retinoic acid is not a standard or indicated treatment for pterygium. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Retinoids bind to nuclear receptors (RAR and RXR) to modulate gene expression. * **Other Ophthalmic Uses:** Topical Vitamin A is also used in **Bitot’s spots** and **Dry Eye Syndrome** (specifically to treat squamous metaplasia of the conjunctiva). * **OSSN Spectrum:** Includes conjunctival intraepithelial neoplasia (CIN) and invasive squamous cell carcinoma. * **Gold Standard for OSSN:** While topical therapy is gaining popularity, the traditional gold standard remains surgical excision with "no-touch" technique and wide margins (4mm).

Q: What is the drug of choice for CMV retinitis in patients with AIDS?

Ganciclovir. **Explanation:** **CMV Retinitis** is the most common opportunistic ocular infection in patients with AIDS, typically occurring when the CD4+ T-lymphocyte count falls below 50 cells/µL. It is characterized by a "pizza-pie" or "cheese and ketchup" fundus appearance due to extensive retinal necrosis and hemorrhage. **Why Ganciclovir is the Correct Answer:** **Ganciclovir** is a nucleoside analogue that inhibits viral DNA polymerase. It is the established **drug of choice** for CMV retinitis. It can be administered intravenously, orally (Valganciclovir), or via intravitreal injections/implants. Valganciclovir (the prodrug) is now frequently used for both induction and maintenance therapy due to its high oral bioavailability. **Analysis of Incorrect Options:** * **A. Acyclovir:** While an antiviral, it is highly effective against Herpes Simplex (HSV) and Varicella-Zoster (VZV) but has **minimal activity** against CMV. * **C. Pentamidine:** This is an antiprotozoal agent used primarily to treat *Pneumocystis jirovecii* pneumonia (PCP) in AIDS patients, not viral infections. * **D. Cotrimoxazole:** This is the drug of choice for the prophylaxis and treatment of *Pneumocystis jirovecii* and *Toxoplasma gondii*, but it has no antiviral properties. **High-Yield Clinical Pearls for NEET-PG:** * **Alternative Drugs:** If Ganciclovir resistance occurs or if there is limiting bone marrow toxicity, **Foscarnet** or **Cidofovir** are used. * **Side Effects:** A classic side effect of Ganciclovir is **bone marrow suppression** (neutropenia/thrombocytopenia), whereas Foscarnet is known for **nephrotoxicity**. * **Fundus Appearance:** Look for "brushfire" borders or "pizza-pie" retinopathy in clinical vignettes. * **Immune Recovery Uveitis (IRU):** Be aware that starting HAART can lead to an inflammatory response in the eye as the immune system recovers.

Question 1

What is the topically used non-selective alpha-agonist in glaucoma?

Accepted Answer

Dipivefrine

Answer

Bimatoprost

Answer

Dorzolamide

Answer

Brimonidine

Question 2

Steroids are contraindicated in which of the following conditions?

Accepted Answer

Dendritic ulcer

Answer

Phlyctenular conjunctivitis

Answer

Granular conjunctivitis

Answer

Mooren's ulcer

Question 3

Bull's eye lesion in the macula is seen with which of the following medications?

Accepted Answer

Chloroquine

Answer

Primaquine

Answer

Quinine

Answer

Sulfamethoxazole

Question 4

Latanoprost is a relatively newer agent. Which of the following statements is true regarding this agent?

Accepted Answer

It is a PGF2a derivative used in glaucoma.

Answer

It is a selective a1 blocker used in benign hypertrophy of the prostate.

Answer

It is a 5a reductase inhibitor used to reduce the size of an enlarged prostate gland.

Answer

It is a PGE2 analogue used intravaginally for cervical priming.

Question 5

Topical Pilocarpine 1% administration failed to produce pupillary constriction in a patient with a large dilated pupil. What is the most probable reason for this failure?

Accepted Answer

Pharmacological blockade

Answer

Adie's tonic pupil

Answer

Uncal herniation

Answer

Diabetic IIIrd cranial nerve palsy

Question 6

What is the most important action of beta-blockers in glaucoma?

Accepted Answer

Decrease in the production of aqueous humor

Answer

Membrane stabilizing effect

Answer

Retinal neuron protecting effect

Answer

Pupillary constriction

Question 7

Which is the fastest acting cycloplegic drug?

Accepted Answer

Tropicamide

Answer

Atropine

Answer

Cyclopentolate

Answer

Homatropine

Question 8

Which of the following is true regarding the ophthalmic use of topical retinoic acid?

Accepted Answer

Ocular-surface squamous neoplasm

Answer

Conjunctival melanoma

Answer

Naevus or congenital moles

Answer

Pterygium

Question 9

What is the drug of choice for CMV retinitis in patients with AIDS?

Accepted Answer

Ganciclovir

Answer

Acyclovir

Answer

Pentamidine

Answer

Cotrimoxazole

Question 10

All of the following are true about antiglaucoma drugs except?

Accepted Answer

Usage of Timolol is unsafe in infants

Answer

PGF2 α analogues increase uveoscleral outflow

Answer

Apraclonidine can lead to lid retraction

Answer

Adrenaline can lead to conjunctival pigmentation

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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