Ophthalmic Pharmacology Practice Questions

Q: Which non-selective beta blocker is commonly used in the management of glaucoma?

Timolol. **Explanation:** **Timolol** is the gold standard and most commonly used non-selective beta-blocker in the management of Open-Angle Glaucoma. It works by blocking $\beta_2$ receptors on the **ciliary epithelium**, thereby reducing the production of aqueous humor. Since it does not affect pupil size or accommodation, it is preferred over miotics. **Analysis of Options:** * **Timolol (Correct):** A potent non-selective $\beta_1$ and $\beta_2$ blocker. It is highly effective in lowering intraocular pressure (IOP) but must be used with caution in patients with asthma or COPD due to potential systemic absorption causing bronchospasm. * **Metoprolol:** This is a cardioselective ($\beta_1$) blocker primarily used in systemic hypertension and cardiology; it is not used topically for glaucoma. * **Betaxolol:** This is a **cardioselective ($\beta_1$)** beta-blocker. While used in glaucoma, it is less effective at lowering IOP than Timolol. However, it is the safest topical beta-blocker for patients with mild respiratory issues because it lacks $\beta_2$ antagonist activity. * **Propranolol:** Although a non-selective beta-blocker, it possesses significant local anesthetic (membrane-stabilizing) activity, which can cause corneal anesthesia and damage if applied topically. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Decreased aqueous secretion (not increased outflow). * **Side Effects:** Bradycardia, heart block, and bronchospasm (due to systemic absorption via the nasolacrimal duct). * **Tip:** To minimize systemic absorption, patients should be advised to perform **punctal occlusion** for 2 minutes after instillation. * **Contraindications:** Bronchial asthma, COPD, 2nd/3rd-degree heart block, and overt heart failure.

Q: Which of the following antiglaucoma drugs can lead to drowsiness?

Brimonidine. **Explanation:** **Brimonidine** is a highly selective **Alpha-2 (α2) adrenergic agonist**. Unlike its predecessor, Apraclonidine, Brimonidine is more lipophilic, allowing it to cross the **blood-brain barrier (BBB)**. Once in the central nervous system, it stimulates α2 receptors in the brainstem, leading to a reduction in sympathetic outflow. This central action commonly results in **drowsiness, fatigue, and lethargy**. Due to this CNS penetration, Brimonidine is strictly **contraindicated in children under 2 years of age**, as it can cause life-threatening apnea, bradycardia, and profound sedation (somnolence). **Analysis of Incorrect Options:** * **Apraclonidine:** While also an α2 agonist, it is more polar and does not cross the BBB effectively. Its primary side effects are local (allergic blepharoconjunctivitis). * **Dipivefrin:** A prodrug of epinephrine (non-selective α and β agonist). It is more likely to cause systemic sympathetic effects like tachycardia or arrhythmias rather than drowsiness. * **Timolol:** A non-selective β-blocker. Its systemic side effects are primarily cardiovascular (bradycardia) and respiratory (bronchospasm), not typically drowsiness. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Brimonidine reduces IOP by both decreasing aqueous humor production and increasing uveoscleral outflow. * **Neuroprotection:** It is often cited as having potential neuroprotective properties for the optic nerve. * **Follicular Conjunctivitis:** This is the most common local side effect of Brimonidine. * **Contraindication:** Avoid in patients taking Monoamine Oxidase Inhibitors (MAOIs) due to the risk of hypertensive crisis.

Q: Which drug should be avoided in a case of spring catarrh?

Antibiotics. **Explanation:** **Spring Catarrh (Vernal Keratoconjunctivitis - VKC)** is a bilateral, recurrent, seasonal allergic inflammation of the conjunctiva, primarily driven by a Type I hypersensitivity reaction to allergens like pollen. **Why Antibiotics are avoided:** The underlying pathology of VKC is **allergic**, not bacterial. Antibiotics have no therapeutic role in treating an allergy. Furthermore, their unnecessary use is contraindicated because: 1. They can cause **medicamentosa** (drug-induced conjunctivitis), worsening the patient's discomfort. 2. They contribute to **antimicrobial resistance**. 3. They may cause hypersensitivity reactions in an already sensitized ocular surface. **Analysis of Incorrect Options:** * **Methylcellulose (Lubricants):** These are beneficial as they provide a barrier against allergens and wash away inflammatory mediators from the ocular surface. * **Steroids:** These are the "gold standard" for managing acute exacerbations of VKC due to their potent anti-inflammatory action. However, they must be used under supervision to avoid glaucoma and cataracts. * **Antihistamines:** These are a mainstay of treatment (often combined with mast cell stabilizers) to provide symptomatic relief from itching. **High-Yield Clinical Pearls for NEET-PG:** * **Hallmark symptoms:** Intense itching, ropy discharge, and photophobia. * **Key signs:** Cobblestone papillae (Palpebral form), Horner-Trantas dots (Limbal form), and Shield ulcers (Corneal involvement). * **Treatment Ladder:** Mast cell stabilizers (Cromolyn) for prophylaxis → Topical Antihistamines → Topical Steroids (for pulses) → Cyclosporine/Tacrolimus (for steroid-sparing).

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: Which agent is used to prevent synechiae after DCR surgery?

Mitomycin. **Explanation:** **Mitomycin C (MMC)** is the correct answer. In the context of Dacryocystorhinostomy (DCR), the primary cause of surgical failure is the formation of fibrous tissue and **synechiae** (adhesions) at the osteotomy site or between the nasal septum and the middle turbinate. MMC is a potent antimetabolite derived from *Streptomyces caespitosus* that inhibits fibroblast proliferation and collagen synthesis by cross-linking DNA. Intraoperative application of low-dose MMC (typically 0.2–0.5 mg/ml) to the osteotomy site significantly reduces scarring, maintains the patency of the stoma, and prevents synechiae formation. **Analysis of Incorrect Options:** * **Tacrolimus:** A calcineurin inhibitor used primarily for refractory vernal keratoconjunctivitis (VKC) or preventing corneal graft rejection. It does not have a primary role in preventing post-DCR fibrosis. * **Cyclosporine:** Another calcineurin inhibitor used for dry eye (Sjögren’s) and VKC. Like Tacrolimus, it modulates T-cell activity but is not used to prevent mechanical synechiae in lacrimal surgery. * **Doxycycline:** An antibiotic with anti-matrix metalloproteinase (MMP) properties. While used in ocular rosacea and persistent epithelial defects, it is not used to prevent adhesions in DCR. **High-Yield Clinical Pearls for NEET-PG:** * **Other uses of MMC in Ophthalmology:** Glaucoma filtering surgery (Trabeculectomy) to prevent bleb failure, Pterygium excision (to prevent recurrence), and Haze prevention after PRK (refractive surgery). * **DCR Success:** The most common site of failure in DCR is the **rhinostomy (stoma) site** due to granulation tissue. * **Alternative:** 5-Fluorouracil (5-FU) is another antimetabolite, but MMC is more potent and more commonly used in DCR.

Q: Ethambutol toxicity primarily affects which aspect of vision?

Green vision. **Explanation:** Ethambutol is a key bacteriostatic drug used in the treatment of Tuberculosis. Its most significant side effect is **dose-dependent optic neuropathy**, which typically presents as a retrobulbar neuritis. **Why Green Vision is Correct:** The earliest clinical sign of ethambutol-induced optic toxicity is a defect in **color vision**, specifically **Red-Green dyschromatopsia**. Among the two, **Green color blindness (deuteranopia)** is often the earliest detectable change. This occurs due to the toxic effect of the drug on the papillomacular bundle of the optic nerve, leading to central or centrocecal scotomas and reduced visual acuity. **Analysis of Incorrect Options:** * **Red Vision (A):** While red-green color blindness occurs, green perception is typically affected first or more prominently in early screening. * **Yellow Vision (C):** Known as xanthopsia, this is classically associated with **Digitalis (Digoxin) toxicity**, not ethambutol. * **Blue Vision (D):** Known as cyanopsia, this is a common side effect of **Sildenafil (Viagra)** due to its inhibition of PDE-6 in the retina. **Clinical Pearls for NEET-PG:** * **Dose:** Toxicity is rare at 15 mg/kg but increases significantly at doses >25 mg/kg. * **Monitoring:** Patients on Ethambutol must undergo baseline and monthly ophthalmic examinations, including **Snellen’s chart** for acuity and **Ishihara plates** for color vision. * **Reversibility:** The toxicity is generally reversible if the drug is discontinued immediately upon the onset of symptoms. * **Mechanism:** It is thought to act as a chelating agent that disrupts copper metabolism within the mitochondria of optic nerve axons.

Question 1

Which non-selective beta blocker is commonly used in the management of glaucoma?

Accepted Answer

Timolol

Answer

Metoprolol

Answer

Betaxolol

Answer

Propranolol

Question 2

All of the following are criteria for high risk of developing chloroquine retinopathy except:

Accepted Answer

> 480g total dose

Answer

Duration of use > 5 years

Answer

Dose of > 250mg/d or > 3mg/kg

Answer

Presence of renal failure

Question 3

Which of the following antiglaucoma drugs can lead to drowsiness?

Accepted Answer

Brimonidine

Answer

Apraclonidine

Answer

Dipevefrine

Answer

Timolol

Question 4

Spring catarrh is treated with which of the following drugs?

Accepted Answer

Olopatadine drops

Answer

Normal saline eye drops

Answer

Ciprofloxacin

Answer

Carboxymethylcellulose (CMC) eye drops

Question 5

Which drug should be avoided in a case of spring catarrh?

Accepted Answer

Antibiotics

Answer

Methylcellulose eyedrops

Answer

Steroids

Answer

Antihistamine

Question 6

Which of the following drugs should not be given in a patient with acute angle-closure glaucoma?

Accepted Answer

Clozapine

Answer

Pilocarpine

Answer

Fluphenazine

Answer

Paroxetine

Question 7

Which of the following medications increases aqueous humor outflow?

Accepted Answer

Latanoprost

Answer

Timolol

Answer

Atropine

Answer

Dorzolamide

Question 8

Which agent is used to prevent synechiae after DCR surgery?

Accepted Answer

Mitomycin

Answer

Tacrolimus

Answer

Cyclosporine

Answer

Doxycycline

Question 9

Which mydriatic is used for refraction in infants?

Accepted Answer

Atropine ointment

Answer

Atropine drops

Answer

Homatropine

Answer

Eucatropine

Question 10

Ethambutol toxicity primarily affects which aspect of vision?

Accepted Answer

Green vision

Answer

Red vision

Answer

Yellow vision

Answer

Blue vision

Ophthalmic Pharmacology — MCQs

Ophthalmic Pharmacology — MCQs

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