Ophthalmic Pharmacology Practice Questions

Q: Which of the following antivirals cannot be used topically in the eye?

Famciclovir. **Explanation:** The correct answer is **Famciclovir**. **1. Why Famciclovir is the correct answer:** Famciclovir is a **prodrug** of penciclovir. It is designed specifically for high oral bioavailability and requires systemic absorption to be converted into its active form by first-pass metabolism in the liver and intestinal wall. Consequently, it is **only available in oral formulations** and cannot be used topically in the eye. In ophthalmic practice, it is primarily used orally for the treatment of Herpes Zoster Ophthalmicus (HZO) and recurrent Herpes Simplex Keratitis. **2. Analysis of Incorrect Options:** * **Acyclovir:** Available as a **3% ophthalmic ointment**. It is a gold standard topical treatment for Herpes Simplex Keratitis (dendritic ulcers) due to its selective toxicity and good corneal penetration. * **Ganciclovir:** Available as a **0.15% ophthalmic gel**. It is highly effective for epithelial keratitis and is often preferred over acyclovir ointment because it is less toxic to the corneal epithelium. * **Idoxuridine:** This was the **first antiviral** developed for topical use (0.1% drops/0.5% ointment). However, it is rarely used today due to significant ocular toxicity and the availability of superior alternatives like Ganciclovir. **3. Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** For Herpes Simplex Epithelial Keratitis, topical **Ganciclovir (0.15% gel)** or **Acyclovir (3% ointment)** are preferred. * **Trifluridine:** Another topical antiviral (1% drops); it is more potent than Idoxuridine but can cause "toxic follicular conjunctivitis." * **Contraindication:** Topical steroids are strictly contraindicated in active dendritic (epithelial) ulcers as they can lead to **"Geographic ulcers."** * **Systemic use:** Oral Famciclovir or Valacyclovir are preferred over oral Acyclovir for Herpes Zoster due to better dosing schedules (TID vs. 5 times/day).

Q: All the following drugs are known to cause anterior uveitis except?

Gatifloxacin. **Explanation:** Drug-induced uveitis is a critical topic in ophthalmic pharmacology. The correct answer is **Gatifloxacin**, as it is not typically associated with anterior uveitis. **1. Why Gatifloxacin is the Correct Answer:** Gatifloxacin is a fourth-generation fluoroquinolone used topically to treat bacterial conjunctivitis and keratitis. While it can cause local irritation or punctate keratitis, it is **not** a recognized cause of anterior uveitis. In contrast, systemic fluoroquinolones (like Moxifloxacin) have been linked to **Bilateral Acute Iris Transillumination (BAIT)**, but Gatifloxacin is generally excluded from the list of classic uveitis-inducing agents. **2. Analysis of Incorrect Options:** * **Rifabutin (Option A):** A potent anti-mycobacterial drug used in HIV patients for MAC prophylaxis. It is a well-known cause of severe, often bilateral, acute anterior uveitis with hypopyon. * **Cidofovir (Option B):** An antiviral used for CMV retinitis. It frequently causes anterior uveitis and hypotony (low IOP) due to its toxic effect on the ciliary body epithelium. * **Metipranolol (Option C):** A non-selective beta-blocker used for glaucoma. It has been specifically linked to granulomatous or non-granulomatous anterior uveitis, a side effect rarely seen with other beta-blockers like Timolol. **Clinical Pearls for NEET-PG:** * **Mnemonic for Uveitis-inducing drugs:** "**S**ubstances **C**ause **R**eal **I**nflammation" (**S**ulfonamides, **C**idofovir, **R**ifabutin, **I**ndinavir/Ibis). * **Bisphosphonates (Zoledronate):** Another high-yield cause of drug-induced uveitis and scleritis. * **Brimonidine:** Can cause a delayed-type hypersensitivity reaction manifesting as granulomatous uveitis. * **Hypopyon Uveitis:** Classically associated with **Rifabutin** and **Behçet’s disease**.

Q: Which of the following cycloplegic agents is considered the strongest?

Atropine. **Explanation:** **1. Why Atropine is Correct:** Atropine is the **strongest and longest-acting** cycloplegic and mydriatic agent available. It is a non-selective muscarinic antagonist that produces profound paralysis of the ciliary muscle (cycloplegia) and the sphincter pupillae (mydriasis). Its maximal cycloplegic effect is reached in 1–3 hours, but the recovery can take up to **7–12 days**. Due to its high potency, it is the gold standard for cycloplegic refraction in children under 5 years of age (especially those with accommodative esotropia), as their ciliary muscle tone is too strong for weaker agents. **2. Why the Other Options are Incorrect:** * **Homatropine (B):** It is about 1/10th as potent as Atropine. It has a shorter duration of action (1–3 days) and is primarily used in treating anterior uveitis to prevent synechiae rather than for refraction. * **Cyclopentolate (C):** While it has a rapid onset (30–60 mins), its potency is less than Atropine. It is the drug of choice for cycloplegic refraction in children aged 5–15 years. * **Tropicamide (D):** It is the **weakest** and shortest-acting agent (duration 4–6 hours). It is the drug of choice for routine fundus examination (mydriasis) but is a poor cycloplegic. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (Refraction):** * <5 years: Atropine (Ointment is preferred over drops to prevent systemic toxicity via nasolacrimal duct). * 5–15 years: Cyclopentolate. * Adults: Homatropine or Tropicamide. * **Antidote:** Physostigmine is used for Atropine poisoning. * **Contraindication:** All cycloplegics are contraindicated in patients with a predisposition to **Angle-Closure Glaucoma**.

Q: Which of the following antiglaucoma drugs can cause stenosis of the nasolacrimal duct?

Timolol. **Explanation:** **Correct Answer: A. Timolol** The correct answer is **Timolol**. Chronic use of certain topical antiglaucoma medications can lead to cicatricial changes in the conjunctiva and the lacrimal drainage system. **Timolol (a non-selective beta-blocker)** and **Echothiophate (a miotic)** are the most commonly implicated agents associated with **nasolacrimal duct (NLD) stenosis** and canalicular obstruction. The underlying mechanism involves drug-induced subepithelial fibrosis and chronic inflammation of the mucosal lining of the lacrimal passages, eventually leading to permanent narrowing or occlusion (secondary acquired lacrimal duct obstruction). **Analysis of Incorrect Options:** * **B. Apraclonidine:** This is an alpha-2 agonist primarily associated with follicular conjunctivitis and eyelid retraction. While it can cause local allergic reactions, it is not a classic cause of NLD stenosis. * **C. Latanoprost:** This prostaglandin analogue is known for causing "Prostaglandin Associated Periorbitopathy" (PAP), which includes deepening of the upper eyelid sulcus, hypertrichosis (increased eyelash growth), and iris hyperpigmentation, but not NLD stenosis. * **D. Adrenaline:** While Adrenaline (and Dipivefrin) can cause the formation of **adrenochrome deposits** (black pigment spots) in the conjunctiva and can rarely cause canalicular blockage due to these deposits, Timolol is the more definitive and classically tested cause of generalized NLD stenosis in this context. **High-Yield Clinical Pearls for NEET-PG:** * **Pilocarpine** and **Phospholine Iodide (Echothiophate)** are also major culprits for punctal and canalicular stenosis. * **Idoxuridine** (antiviral) is another high-yield drug known for causing lacrimal scarring. * To minimize systemic absorption and local side effects of Timolol, patients should be advised to perform **punctal occlusion** for 2 minutes after instillation.

Q: Which of the following is NOT used as a local injection for ophthalmic use?

Prednisolone. **Explanation:** The correct answer is **Prednisolone (Option B)**. In ophthalmic practice, corticosteroids are administered via various routes depending on the target tissue. **Prednisolone** is highly effective as a topical drop (Prednisolone acetate 1%) for anterior segment inflammation because of its excellent biphasic solubility, which allows it to penetrate the cornea. However, it is **not formulated for local injection** (subconjunctival, sub-Tenon, or intravitreal) because it lacks the necessary pharmacological properties (such as depot formulation or specific pH stability) required for safe and effective intraocular or periocular injection. **Analysis of Incorrect Options:** * **Triamcinolone (Option A):** Commonly used as a **depot injection** (e.g., Triamcinolone acetonide). It is injected into the sub-Tenon space for uveitis or intravitreally to treat macular edema. It is also used to visualize the vitreous during vitrectomy. * **Betamethasone (Option C):** Often used as a **subconjunctival injection** post-operatively to control inflammation. It has a rapid onset and is frequently combined with dexamethasone in clinical practice. * **Dexamethasone (Option D):** Available in both short-acting (sodium phosphate) and long-acting (intravitreal implants like **Ozurdex**) forms. It is a potent steroid used for posterior segment pathologies. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Anterior Uveitis:** Topical Prednisolone acetate (1%). * **Steroid-Induced Glaucoma:** Most common with topical steroids; least common with systemic steroids. * **Intravitreal Implants:** Dexamethasone (Ozurdex) and Fluocinolone (Iluvien) are the primary steroids used as sustained-release implants. * **Side Effects:** All local steroid injections carry the risk of secondary glaucoma and posterior subcapsular cataracts (PSC).

Q: During intraocular lens implantation, corneal endothelial damage can be prevented by the use of which of the following agents?

All of the above. **Explanation:** The correct answer is **D. All of the above**. These agents belong to a class of drugs known as **Ophthalmic Viscosurgical Devices (OVDs)** or viscoelastics. **Underlying Medical Concept:** The corneal endothelium is a non-regenerative monolayer of cells responsible for maintaining corneal transparency. During intraocular surgeries like cataract extraction and IOL implantation, the endothelium is at high risk of mechanical trauma from surgical instruments, ultrasound energy (phacoemulsification), and the IOL itself. OVDs are used to maintain the anterior chamber depth, provide a physical cushion to protect endothelial cells, and coat surgical instruments/IOLs to reduce friction. **Analysis of Options:** * **Methylcellulose (Hydroxypropyl Methylcellulose - HPMC):** A common dispersive OVD. It is synthetic, non-antigenic, and provides excellent coating properties for the cornea and instruments. * **Sodium Hyaluronate:** A cohesive OVD naturally found in the vitreous humor. It is highly effective at maintaining space and protecting the endothelium due to its high molecular weight and viscosity. * **Chondroitin Sulfate:** Often used in combination with sodium hyaluronate (e.g., Viscoat). It has excellent dispersive properties, adhering to the endothelium to provide a protective shield throughout the procedure. **High-Yield Clinical Pearls for NEET-PG:** * **Classification:** OVDs are classified into **Cohesive** (maintain space, e.g., Sodium Hyaluronate) and **Dispersive** (coat surfaces, e.g., HPMC, Chondroitin Sulfate). * **Complication:** The most common postoperative complication of OVD use is a transient **rise in Intraocular Pressure (IOP)** due to mechanical blockage of the trabecular meshwork if the agent is not thoroughly aspirated. * **Ideal OVD:** Should be transparent, non-toxic, non-pyrogenic, and easily removable from the eye.

Q: Iris cysts are prevented by which medication?

Phenylephrine. **Explanation:** The correct answer is **Phenylephrine**. **Mechanism and Rationale:** Iris cysts (specifically miotic-induced cysts) are a known side effect of long-term use of potent, long-acting cholinesterase inhibitors (miotics) like **Echothiophate**. These cysts form at the pupillary margin due to the proliferation of the iris pigment epithelium. The underlying medical concept is that **Phenylephrine (2.5%)**, a sympathomimetic alpha-1 agonist, acts as a competitive stabilizer. When used concurrently with miotics, it prevents the hypertrophy and cystic changes of the pigment epithelium without neutralizing the pressure-lowering effect of the miotic. **Analysis of Incorrect Options:** * **Atropine (A):** This is a potent parasympatholytic (mydriatic-cycloplegic). While it dilates the pupil, it is not used to prevent cysts caused by miotics; in fact, its clinical action is the polar opposite of the drugs that cause the cysts. * **Pilocarpine (B):** This is a direct-acting miotic. While it can occasionally cause iris cysts, they are much more common with long-acting indirect miotics. It does not prevent them. * **Echothiophate (D):** This is an irreversible cholinesterase inhibitor and is the **primary cause** of these iris cysts, not the preventive agent. **Clinical Pearls for NEET-PG:** * **Echothiophate** is the most common culprit for iris cysts in children being treated for accommodative esotropia. * **Phenylephrine 2.5%** is the specific concentration used to prevent these cysts. * **Other side effects of Echothiophate:** Retinal detachment, cataract formation (anterior subcapsular), and prolonged apnea if succinylcholine is administered during anesthesia (due to depleted plasma pseudocholinesterase).

Question 1

Which of the following antivirals cannot be used topically in the eye?

Accepted Answer

Famciclovir

Answer

Acyclovir

Answer

Ganciclovir

Answer

Idoxuridine

Question 2

All the following drugs are known to cause anterior uveitis except?

Accepted Answer

Gatifloxacin

Answer

Rifabutin

Answer

Cidofovir

Answer

Metipranolol

Question 3

Intraocular tension is decreased by all except?

Accepted Answer

Atropine

Answer

Pilocarpine

Answer

Apraclonidine

Answer

Tropicamide

Question 4

Brinzolamide is:

Accepted Answer

A non-competitive and reversible carbonic anhydrase inhibitor

Answer

A competitive and reversible carbonic anhydrase inhibitor

Answer

A competitive and irreversible carbonic anhydrase inhibitor

Answer

A non-competitive and irreversible carbonic anhydrase inhibitor

Question 5

Which of the following local anesthetic agents is the drug of choice for removal of corneal foreign bodies?

Accepted Answer

Tetracaine

Answer

Benzocaine

Answer

Lignocaine

Answer

Prilocaine

Question 6

Which of the following cycloplegic agents is considered the strongest?

Accepted Answer

Atropine

Answer

Homatropine

Answer

Cyclopentolate

Answer

Tropicamide

Question 7

Which of the following antiglaucoma drugs can cause stenosis of the nasolacrimal duct?

Accepted Answer

Timolol

Answer

Apraclonidine

Answer

Latanoprost

Answer

Adrenaline

Question 8

Which of the following is NOT used as a local injection for ophthalmic use?

Accepted Answer

Prednisolone

Answer

Triamcinolone

Answer

Betamethasone

Answer

Dexamethasone

Question 9

During intraocular lens implantation, corneal endothelial damage can be prevented by the use of which of the following agents?

Accepted Answer

All of the above

Answer

Methyl cellulose

Answer

Sodium hyaluronate

Answer

Chondroitin sulfate

Question 10

Iris cysts are prevented by which medication?

Accepted Answer

Phenylephrine

Answer

Atropine

Answer

Pilocarpine

Answer

Ecothiopate

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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