Diseases of the Cornea Practice Questions

Q: A patient using a contact lens develops a corneal infection. Laboratory diagnosis of acanthamoeba keratitis was established. Which of the following is the best drug for treatment?

Polyhexamethylene biguanide. **Explanation:** **Acanthamoeba keratitis** is a vision-threatening infection typically associated with contact lens wearers (often due to poor hygiene or use of tap water). The organism exists in two forms: the active **trophozoite** and the highly resistant **double-walled cyst**. **1. Why Polyhexamethylene Biguanide (PHMB) is the Correct Answer:** PHMB (0.02%) is considered the first-line treatment because it is a **biguanide** with potent cysticidal activity. It acts by disrupting the cytoplasmic membrane of the organism. Unlike many other agents, biguanides (PHMB and Chlorhexidine) can effectively penetrate and kill the dormant cyst stage, which is crucial for preventing recurrence. **2. Analysis of Incorrect Options:** * **Propamidine (Brolene):** This is a diamidine. While it was historically the treatment of choice, it is less effective than PHMB when used as monotherapy and is associated with significant corneal toxicity. It is now often used as an adjuvant rather than the primary drug. * **Neosporin:** This is a combination of Neomycin, Polymyxin B, and Bacitracin. While Neomycin has some anti-acanthamoebic activity, it is insufficient to treat the infection alone and is primarily used to prevent secondary bacterial infections. * **Ketoconazole:** This is an antifungal. While systemic or topical antifungals (like Voriconazole) are sometimes used as adjuncts in refractory cases, they are not the primary treatment for Acanthamoeba. **3. High-Yield Clinical Pearls for NEET-PG:** * **Classic Presentation:** Severe ocular pain that is **"out of proportion"** to the clinical signs. * **Pathognomonic Sign:** **Radial Keratoneuritis** (infiltration along corneal nerves). * **Late Sign:** Ring-shaped corneal infiltrate. * **Gold Standard Culture:** Non-nutrient agar (NNA) seeded with *E. coli*. * **Stains:** Calcofluor white (fluorescent) or Periodic acid-Schiff (PAS).

Q: Which of the following are types of corneal dystrophies?

Macular, Granular, Lattice, Fuchs. **Explanation:** Corneal dystrophies are a group of genetic, bilateral, symmetric, and slowly progressive corneal opacifications that are not associated with inflammation or systemic disease. They are classified based on the layer of the cornea they affect. **Why Option D is Correct:** The correct answer includes four classic types of corneal dystrophies: * **Macular, Granular, and Lattice Dystrophies:** These are the primary **stromal dystrophies**. * **Fuchs’ Endothelial Corneal Dystrophy (FECD):** This is the most common **posterior (endothelial) dystrophy**, characterized by "guttae" and stromal edema. **Why Other Options are Incorrect:** Options A, B, and C are incorrect because they include **Mooren’s Ulcer**. Mooren’s ulcer is an idiopathic, peripheral ulcerative keratitis (PUK) that is inflammatory and often painful. It is **not** a dystrophy; it is an autoimmune-mediated destruction of the corneal stroma. **NEET-PG High-Yield Clinical Pearls:** To differentiate stromal dystrophies, remember the mnemonic **"Marilyn Monroe Got Herself Some Lettuce In City"**: 1. **M**acular – **M**ucopolysaccharide – **A**lcian Blue (Most severe, Autosomal Recessive). 2. **G**ranular – **H**yaline – **S**affron/Masson Trichrome (Breadcrumb appearance). 3. **L**attice – **A**myloid – **C**ongo Red (Refractile lines, Apple-green birefringence). * **Inheritance:** Most dystrophies are Autosomal Dominant, **except Macular**, which is Autosomal Recessive. * **Fuchs’ Dystrophy:** Look for "beaten metal appearance" on specular microscopy and the hallmark symptom of early morning blurring of vision.

Q: Keratomalacia is due to which deficiency?

Vitamin A deficiency. **Explanation:** **Keratomalacia** is the most severe ocular manifestation of **Vitamin A deficiency**. Vitamin A (Retinol) is essential for maintaining the integrity of epithelial surfaces. In its absence, the conjunctival and corneal epithelium undergo **squamous metaplasia**, losing their goblet cells and ability to secrete mucus. This leads to extreme dryness (xerosis). If untreated, the cornea undergoes **liquefactive necrosis**, leading to softening, stromal melting, and potential perforation. This rapid destruction is what defines keratomalacia. **Analysis of Options:** * **Vitamin A deficiency (Correct):** It is the primary cause of Xerophthalmia, a spectrum of eye signs ranging from night blindness (Nyctalopia) to Bitot’s spots, corneal xerosis, and finally, keratomalacia. * **Keratoconus:** This is a non-inflammatory, progressive thinning and cone-like ectasia of the cornea, typically associated with collagen disorders or eye rubbing, not nutritional deficiencies. * **Vitamin E deficiency:** While Vitamin E is an antioxidant, its deficiency primarily manifests as neuromuscular issues (ataxia) and hemolytic anemia, not corneal melting. * **Retinitis pigmentosa:** This is a genetic dystrophy of the retinal photoreceptors (rods and cones) leading to tunnel vision and night blindness, but it does not affect the structural integrity of the cornea. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** X1A (Conjunctival xerosis), X1B (**Bitot’s spots**—foamy patches on bulbar conjunctiva), X2 (Corneal xerosis), X3A (Keratomalacia 1/3rd cornea). * **Treatment:** Immediate administration of Vitamin A (200,000 IU orally on days 0, 1, and 14). * **Earliest Symptom:** Night blindness (Nyctalopia). * **Earliest Sign:** Conjunctival xerosis.

Q: Fleischer ring is due to which type of deposition?

Iron deposition. **Explanation:** **1. Why Iron Deposition is Correct:** The **Fleischer ring** is a classic clinical sign of **Keratoconus**. It consists of a partial or complete yellowish-to-brown ring located at the base of the cone in the corneal epithelium. It is caused by the deposition of **hemosiderin (iron)** within the basal epithelial cells. The iron accumulates due to the pooling of tears in the gutter created by the thinning and protrusion of the cornea. **2. Why Other Options are Incorrect:** * **Copper deposition:** This is associated with the **Kayser-Fleischer (KF) ring**, seen in **Wilson’s disease**. Unlike the Fleischer ring, the KF ring occurs in the **Descemet’s membrane** at the limbus. * **Aluminum and Molybdenum:** These metals are not typically associated with specific, named corneal ring depositions in clinical ophthalmology. **3. High-Yield Clinical Pearls for NEET-PG:** * **Fleischer Ring vs. Kayser-Fleischer Ring:** Do not confuse them. Fleischer = Keratoconus (Iron); Kayser-Fleischer = Wilson’s Disease (Copper). * **Other Iron Lines in the Cornea:** * **Hudson-Stahli line:** Found at the junction of the upper 2/3 and lower 1/3 of the cornea (age-related). * **Stocker’s line:** Found at the head of a Pterygium. * **Ferry’s line:** Found at the edge of a filtering bleb (Glaucoma surgery). * **Keratoconus Signs:** Look for Munson’s sign (V-shaped indentation of lower lid on downgaze), Vogt’s striae (vertical stress lines), and Rizutti’s sign.

Q: Cornea melts without inflammation in which condition?

Keratomalacia. **Explanation:** The hallmark of **Keratomalacia** is the rapid, liquefactive necrosis of the corneal stroma in a **"quiet eye"** (absence of significant inflammation). This condition is the end-stage ocular manifestation of severe **Vitamin A deficiency**. Vitamin A is essential for maintaining the health of epithelial surfaces; its deficiency leads to squamous metaplasia and loss of goblet cells. Without adequate mucus and epithelial integrity, the cornea undergoes "melting" due to the activation of collagenases and proteases, often leading to perforation if not treated urgently. **Analysis of Incorrect Options:** * **Gout:** While it can cause scleritis or episcleritis, it does not typically cause non-inflammatory corneal melting. * **Sarcoidosis:** This is a granulomatous multi-system disorder. Ocular involvement usually presents as granulomatous uveitis or lacrimal gland enlargement, rather than stromal melting. * **Rheumatoid Arthritis (RA):** RA is a common cause of **Peripheral Ulcerative Keratitis (PUK)** or "melting." However, in RA, the process is typically **inflammatory** (vasculitis-mediated) and associated with significant pain and perilimbic injection, unlike the "quiet" melt of keratomalacia. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** X1A (Conjunctival xerosis), X1B (Bitot’s spots), X2 (Corneal xerosis), **X3A/X3B (Keratomalacia)**. * **Bitot’s Spots:** Triangular, foamy patches on the bulbar conjunctiva (usually temporal) caused by *Corynebacterium xerosis*. * **Nyctalopia (Night blindness):** The earliest clinical symptom of Vitamin A deficiency. * **Treatment:** Immediate high-dose Vitamin A supplementation (200,000 IU orally on days 0, 1, and 14).

Q: Kayser-Fleischer rings are characteristic of which condition?

Wilson disease. **Explanation:** **Wilson Disease (Hepatolenticular Degeneration)** is the correct answer. The Kayser-Fleischer (KF) ring is a hallmark clinical sign of this autosomal recessive disorder characterized by abnormal copper metabolism. Due to a deficiency in the copper-transporting protein **ceruloplasmin**, copper deposits in various tissues. In the eye, copper accumulates specifically in the **Descemet’s membrane** of the peripheral cornea. * **Clinical Appearance:** It appears as a golden-brown or greenish-brown ring at the limbus. It is best visualized using a **Slit-lamp examination**, though it may be visible to the naked eye in advanced cases. * **Significance:** It is present in 95% of patients with neurological symptoms and about 50-60% of those with hepatic presentations. Notably, the ring disappears with effective chelation therapy (e.g., Penicillamine). **Analysis of Incorrect Options:** * **A. Hemosiderosis:** Iron deposition in the cornea typically forms a **Hudson-Stahli line** (iron line in the epithelium) or occurs following a metallic foreign body, but not a KF ring. * **C. Tyrosinemia:** Type II Tyrosinemia (Richner-Hanhart syndrome) presents with **pseudodendritic keratitis** and painful palmoplantar hyperkeratosis, not copper deposition. * **D. Hereditary cataract:** This refers to lens opacification from birth/childhood and does not involve corneal pigment rings. **High-Yield Pearls for NEET-PG:** 1. **Sunflower Cataract:** Another ocular feature of Wilson disease (copper deposition in the anterior lens capsule). 2. **Fleischer Ring:** Do not confuse with KF ring; Fleischer rings are iron deposits seen at the base of the cone in **Keratoconus**. 3. **Chalcosis:** The term for intraocular copper deposition (usually from a foreign body).

Q: A 30-year-old male from a rural background presents with a 10-day history of difficulty in vision. He reports vegetative material falling into his left eye 15 days prior. Examination reveals an ulcerative lesion in the cornea with feathery margins and creamy exudates, along with a few satellite lesions. What is the most likely etiologic agent?

Fusarium sp.. ### Explanation **Correct Option: B. Fusarium sp.** The clinical presentation is classic for **Fungal Keratitis (Keratomycosis)**. The key diagnostic clues in the history and examination are: 1. **History of trauma with vegetative material:** This is the most significant risk factor for fungal corneal ulcers, especially in rural settings. 2. **Feathery margins:** Fungal hyphae infiltrate the corneal stroma, creating a characteristic "branching" or feathery appearance. 3. **Satellite lesions:** These are small, isolated infiltrates surrounding the main ulcer, representing the spread of fungal elements. 4. **Creamy exudates/Hypopyon:** Fungal ulcers often present with a thick, "fixed" hypopyon. Among fungi, **Fusarium** and **Aspergillus** are the most common filamentous fungi causing keratitis in India. **Analysis of Incorrect Options:** * **A. Corynebacterium diphtheria:** This is a rare cause of membranous conjunctivitis. While it can penetrate an intact corneal epithelium, it does not present with feathery margins or a history of vegetative trauma. * **C. Acanthamoeba sp.:** Typically associated with **contact lens wear** or exposure to contaminated water. It is characterized by intense pain (out of proportion to clinical signs) and a **ring-shaped infiltrate**. * **D. Streptococcus pneumoniae:** A common cause of bacterial keratitis (Ulcus Serpens). It typically presents with a **serpiginous (creeping) ulcer** with a sharp overhanging border and an associated hypopyon, but lacks feathery margins and satellite lesions. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Corneal scraping followed by **KOH mount** (shows hyphae) and culture on **Sabouraud’s Dextrose Agar (SDA)**. * **Drug of Choice:** Topical **Natamycin (5%)** is the first-line treatment for filamentous fungi like *Fusarium*. * **Clinical Sign:** Fungal ulcers are often "dry" in appearance and may have an immune ring (Wessely ring).

Q: In which one of the following infections is a dendritic ulcer seen?

Herpes simplex. **Explanation:** The hallmark of **Herpes Simplex Keratitis (HSK)** is the **dendritic ulcer**. This occurs due to the active replication of the Herpes Simplex Virus (HSV-1) in the corneal epithelium, leading to cell lysis. **Why Herpes Simplex is correct:** The ulcer is characterized by a linear, branching (arborescent) pattern with **terminal bulbs** (knobs) at the ends of the branches. These bulbs contain live virus. A key clinical feature is **decreased corneal sensations** due to viral damage to the trigeminal nerve endings. Staining with Rose Bengal or Lissamine Green highlights the devitalized cells at the ulcer margins, while Fluorescein stains the basement membrane in the center. **Why other options are incorrect:** * **Measles:** Typically causes a **superficial punctate keratitis** (SPK) rather than a dendritic pattern. * **Pseudomonas:** Causes a rapidly progressing **suppurative bacterial ulcer** characterized by a "soupy" appearance and greenish-blue discharge. * **Gonococcal infection:** Causes a hyperacute purulent conjunctivitis that can lead to corneal perforation; it is unique because *N. gonorrhoeae* can **penetrate an intact corneal epithelium**. **High-Yield Clinical Pearls for NEET-PG:** * **Geographic Ulcer:** Formed when a dendritic ulcer enlarges (often due to inappropriate use of topical steroids). * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir. *Note: Steroids are contraindicated in epithelial (dendritic) keratitis but used in stromal (disciform) keratitis.* * **Differential Diagnosis:** "Pseudo-dendrites" (no terminal bulbs) are seen in **Acanthamoeba keratitis**, Herpes Zoster Ophthalmicus, and Tyrosinemia Type II.

Question 1

A patient using a contact lens develops a corneal infection. Laboratory diagnosis of acanthamoeba keratitis was established. Which of the following is the best drug for treatment?

Accepted Answer

Polyhexamethylene biguanide

Answer

Propamidine

Answer

Neosporin

Answer

Ketoconazole

Question 2

Herpes zoster ophthalmicus is defined as:

Accepted Answer

Reactivation of herpes zoster virus in the trigeminal nerve.

Answer

Reactivation of herpes simplex virus in the optic nerve.

Answer

Reactivation of herpes simplex virus in the oculomotor nerve.

Answer

Herpes infection in an immunocompromised patient.

Question 3

Which of the following are types of corneal dystrophies?

Accepted Answer

Macular, Granular, Lattice, Fuchs

Answer

Granular, Lattice, Mooren, Fuchs

Answer

Macular, Granular, Lattice, Mooren

Answer

Macular, Lattice, Mooren, Fuchs

Question 4

Keratomalacia is due to which deficiency?

Accepted Answer

Vitamin A deficiency

Answer

Keratoconus

Answer

Vitamin E deficiency

Answer

Retinitis pigmentosa

Question 5

Fleischer ring is due to which type of deposition?

Accepted Answer

Iron deposition

Answer

Copper deposition

Answer

Aluminum deposition

Answer

Molybdenum deposition

Question 6

Cornea melts without inflammation in which condition?

Accepted Answer

Keratomalacia

Answer

Gout

Answer

Sarcoidosis

Answer

Rheumatoid arthritis

Question 7

A satellite lesion in a corneal ulcer with a feathery margin and fixed hypopyon is a feature of which of the following?

Accepted Answer

Fungal keratitis

Answer

Trachoma

Answer

Angular conjunctivitis

Answer

Herpes simplex keratitis

Question 8

Kayser-Fleischer rings are characteristic of which condition?

Accepted Answer

Wilson disease

Answer

Hemosiderosis

Answer

Tyrosinemia

Answer

Hereditary cataract

Question 9

A 30-year-old male from a rural background presents with a 10-day history of difficulty in vision. He reports vegetative material falling into his left eye 15 days prior. Examination reveals an ulcerative lesion in the cornea with feathery margins and creamy exudates, along with a few satellite lesions. What is the most likely etiologic agent?

Accepted Answer

Fusarium sp.

Answer

Corynebacterium diphtheria

Answer

Acanthomoeba sp.

Answer

Streptococcus pneumoniae

Question 10

In which one of the following infections is a dendritic ulcer seen?

Accepted Answer

Herpes simplex

Answer

Measles

Answer

Pseudomonas

Answer

Gonococcal infection

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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