Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 301: What is keratomalacia?

A. Occurs due to Vitamin A deficiency (Correct Answer)
B. A relatively benign condition
C. The first feature of Vitamin A deficiency
D. Also seen in retinitis pigmentosa

Explanation: **Explanation:** **Keratomalacia** is the most severe ocular manifestation of **Vitamin A deficiency (Xerophthalmia)**. It is characterized by the rapid liquefactive necrosis of the corneal stroma, leading to corneal melting, perforation, and eventual blindness. * **Why Option A is correct:** Vitamin A is essential for maintaining the health of epithelial surfaces. Its deficiency leads to squamous metaplasia of the conjunctiva and cornea. In advanced stages (WHO Grade X3), the cornea loses its structural integrity and undergoes "melting" or malacia, hence the name Keratomalacia. * **Why Option B is incorrect:** Keratomalacia is a **medical emergency**, not a benign condition. It is a sign of profound systemic Vitamin A depletion and is often associated with high mortality rates in children due to concurrent malnutrition or infections like measles. * **Why Option C is incorrect:** The first clinical feature of Vitamin A deficiency is **Night Blindness (Nyctalopia)**, followed by Conjunctival Xerosis and Bitot’s spots. Keratomalacia is a late-stage manifestation. * **Why Option D is incorrect:** Retinitis Pigmentosa is a genetic dystrophy of the photoreceptors (rods and cones). While it also causes night blindness, it is unrelated to the nutritional deficiency that causes Keratomalacia. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** * X1A: Conjunctival xerosis * X1B: Bitot’s spots (triangular, foamy patches) * X2: Corneal xerosis * **X3A/X3B: Keratomalacia** (<1/3 or >1/3 of corneal surface) * **Treatment:** Immediate administration of Vitamin A (200,000 IU orally on days 0, 1, and 14). * **Key Sign:** Keratomalacia is typically **painless** and bilateral, but often asymmetrical.

Question 302: Orange-skin cornea results due to:

A. Chalcosis
B. Siderosis
C. Ammonia burn
D. Mustard gas (Correct Answer)

Explanation: **Explanation:** **Mustard Gas (Correct Answer):** Mustard gas (sulfur mustard) is a potent alkylating agent used in chemical warfare. Ocular exposure leads to a delayed-onset keratitis that can manifest years after the initial insult. The characteristic **"Orange-skin cornea"** (also known as *peau d'orange* appearance) occurs due to chronic subepithelial changes, lipid deposition, and scarring that creates a granular, pitted, and orange-tinted texture on the corneal surface. This is often associated with "delayed mustard gas keratitis," characterized by vascularization and recurrent ulceration. **Incorrect Options:** * **A. Chalcosis:** This refers to the intraocular deposition of copper. In the cornea, it typically presents as a **Kayser-Fleischer (KF) ring** (golden-brown/greenish deposit in Descemet’s membrane) or a "sunflower cataract" in the lens. * **B. Siderosis:** This is caused by an iron-containing intraocular foreign body. It leads to rust-colored staining of the lens (anterior subcapsular) and iris, but not an orange-skin corneal texture. * **C. Ammonia burn:** This is a severe alkali burn. It causes rapid liquefactive necrosis, leading to corneal opacification ("ground glass" appearance), limbal ischemia, and potential perforation, rather than a chronic orange-skin texture. **Clinical Pearls for NEET-PG:** * **Mustard Gas:** Look for the triad of "delayed keratitis," "limbal ischemia," and "orange-skin cornea." * **Vossius Ring:** A circular ring of pigment on the anterior lens capsule following blunt trauma. * **Fleck Keratopathy:** Often confused with mustard gas changes but is a distinct congenital dystrophy. * **Hudson-Stahli line:** An iron deposit line seen at the junction of the upper 2/3 and lower 1/3 of the cornea in elderly patients (normal aging).

Question 303: Keratic precipitates are most commonly seen in which condition?

A. Corneal ulcers
B. Uveitis (Correct Answer)
C. Nuclear cataracts
D. Keratoconus

Explanation: **Explanation:** **Keratic Precipitates (KPs)** are inflammatory cell deposits on the **corneal endothelium**. They are a hallmark clinical sign of **anterior uveitis** (iridocyclitis). 1. **Why Uveitis is Correct:** In uveitis, the blood-aqueous barrier is breached, allowing inflammatory cells (leukocytes) and protein to enter the anterior chamber. These cells circulate via convection currents in the aqueous humor and eventually settle and adhere to the sticky, inflamed corneal endothelium, forming KPs. 2. **Why Other Options are Incorrect:** * **Corneal Ulcers:** These involve the corneal epithelium and stroma. While they may cause a secondary "sterile" aqueous flare, KPs are not their primary diagnostic feature. * **Nuclear Cataracts:** This is a degenerative/age-related change of the crystalline lens fibers and does not involve inflammatory deposits on the cornea. * **Keratoconus:** This is a non-inflammatory ectatic dystrophy characterized by corneal thinning and cone-shaped protrusion. Key signs include Munson’s sign, Fleischer’s ring, and Vogt’s striae, but not KPs. **High-Yield Clinical Pearls for NEET-PG:** * **Arlt’s Triangle:** KPs typically settle in a triangular distribution on the inferior part of the cornea due to gravity and convection currents. * **Mutton-fat KPs:** Large, greasy-looking precipitates (composed of macrophages) characteristic of **Granulomatous Uveitis** (e.g., Sarcoidosis, TB). * **Small/Fine KPs:** Composed of neutrophils and lymphocytes, seen in **Non-granulomatous Uveitis**. * **Stellate KPs:** Distributed over the entire endothelium; classic for **Fuchs’ Heterochromic Iridocyclitis** and Viral Uveitis.

Question 304: A patient presents with a fixed dilated pupil, iris atrophy, and secondary glaucoma following penetrating keratoplasty. What condition is this suggestive of?

A. Benedict's syndrome
B. Posner-Schlossman syndrome
C. Kaufmann's syndrome
D. Uretes Zavalia syndrome (Correct Answer)

Explanation: **Explanation:** **Urrets-Zavalia Syndrome (UZS)** is a rare but classic complication characterized by a **permanently fixed, dilated pupil** associated with iris atrophy and secondary glaucoma. It most commonly occurs following **penetrating keratoplasty (PKP)** for keratoconus, though it has also been reported after Deep Anterior Lamellar Keratoplasty (DALK) and other intraocular procedures. The underlying pathophysiology is believed to be **iris ischemia**. This occurs due to a sudden rise in intraocular pressure (IOP) post-operatively (often from viscoelastic retention or pupillary block), which compresses the iris root and its vasculature against the peripheral cornea or the surgical wound, leading to sphincter muscle necrosis. **Analysis of Incorrect Options:** * **Benedict’s Syndrome:** This is a midbrain stroke syndrome (Weber’s variant) involving the 3rd nerve fascicles and the red nucleus, presenting with ipsilateral CN III palsy and contralateral tremors/ataxia. It is not an ocular surgical complication. * **Posner-Schlossman Syndrome (Glaucomatocyclitic Crisis):** Characterized by recurrent episodes of very high IOP with mild anterior uveitis and fine keratic precipitates. The pupil is typically normal or slightly sluggish, not permanently fixed/atrophic. * **Kaufmann’s Syndrome:** This is not a recognized eponym in this clinical context. (Note: Herbert Kaufman is a famous cornea specialist, but no such syndrome exists for post-PKP mydriasis). **High-Yield Clinical Pearls for NEET-PG:** * **Classic Association:** Penetrating Keratoplasty for **Keratoconus**. * **Risk Factor:** Use of strong mydriatics (like Atropine) post-operatively in the presence of high IOP. * **Clinical Features:** Fixed mydriasis, iris thinning/atrophy, and **ectropion uveae**. * **Prevention:** Ensure complete removal of viscoelastics and monitor IOP closely in the immediate post-operative period.

Question 305: Where are stem cells located in the cornea?

A. Limbus (Correct Answer)
B. Stroma
C. Epithelium
D. Descemet's membrane

Explanation: **Explanation:** The correct answer is **Limbus**. **1. Why Limbus is Correct:** The corneal epithelium is a non-keratinized stratified squamous epithelium that undergoes constant turnover. The source of these new cells is the **Limbal Stem Cells (LSCs)**, located in the **Palisades of Vogt** within the limbus (the junction between the cornea and the sclera). These stem cells act as a barrier to prevent the overgrowth of conjunctival tissue onto the clear cornea and provide a continuous supply of transient amplifying cells that migrate centripetally to replenish the corneal surface. **2. Why Other Options are Incorrect:** * **Stroma:** This is the thickest layer of the cornea, composed primarily of collagen fibers and keratocytes. It provides structural integrity but does not house epithelial stem cells. * **Epithelium:** While the epithelium contains the daughter cells (transient amplifying cells), the actual *progenitor* stem cells are not located in the central cornea; they reside peripherally at the limbus. * **Descemet's Membrane:** This is the basement membrane of the endothelium. It is an acellular layer and does not possess regenerative stem cell properties. **3. Clinical Pearls for NEET-PG:** * **Limbal Stem Cell Deficiency (LSCD):** Results in "conjunctivalization" of the cornea (neovascularization and opaque surface), commonly seen after chemical burns or in Stevens-Johnson Syndrome. * **Palisades of Vogt:** These are radial fibrovascular ridges in the limbus that serve as the anatomical niche for stem cells. * **Thoft’s XYZ Hypothesis:** Explains corneal epithelial maintenance: **X** (proliferation of basal cells), **Y** (centripetal migration of limbal cells), and **Z** (desquamation of surface cells).

Question 306: Treatment for dendritic ulcer includes all except:

A. Penetrating keratoplasty
B. Acyclovir
C. Steroids (Correct Answer)
D. Debridement of the edges of the ulcer

Explanation: **Explanation:** Dendritic ulcers are the hallmark of **Herpes Simplex Keratitis (HSK)**, specifically the epithelial stage. The primary pathology is active viral replication within the corneal epithelial cells. **Why Steroids are Contraindicated (Correct Answer):** Topical steroids are strictly **contraindicated** in the presence of an active dendritic ulcer. Steroids suppress the local immune response and promote viral replication. This can lead to the expansion of the ulcer into a "geographic ulcer" and may facilitate stromal invasion or corneal perforation. **Analysis of Other Options:** * **Acyclovir (3% Ointment):** This is the standard antiviral treatment. It works by inhibiting viral DNA polymerase, thereby stopping replication. * **Debridement:** Mechanical debridement of the ulcer edges (which contain the highest load of live virus) helps reduce the viral load and allows for faster healing and better penetration of antiviral drugs. * **Penetrating Keratoplasty (PK):** While not the first-line treatment for an *active* ulcer, "therapeutic PK" may be indicated in cases of impending or actual corneal perforation resulting from complications of the ulcer. **NEET-PG High-Yield Pearls:** * **Morphology:** Dendritic ulcers have a linear, branching pattern with characteristic **terminal bulbs** (knobs) that stain with Fluorescein. The bed stains with Fluorescein, while the margins (containing virus) stain with **Rose Bengal**. * **Sensation:** Corneal sensations are typically **reduced or absent** (hypoesthesia) in HSK. * **Steroid Exception:** Steroids are only used in HSK for **Disciform Keratitis** (stromal involvement), which is an immune-mediated reaction, but *only* under the cover of topical antivirals.

Question 307: Interstitial keratitis is commonly seen in:

A. Fungal keratitis
B. Congenital syphilis (Correct Answer)
C. Phlyctenular keratitis
D. Trachoma

Explanation: **Explanation:** **Interstitial Keratitis (IK)** is a chronic non-ulcerative inflammation of the corneal stroma without involvement of the epithelium or endothelium. It is an immune-mediated response to a systemic infection rather than a direct invasion by the pathogen. **Why Congenital Syphilis is Correct:** Congenital syphilis is the most common cause of bilateral interstitial keratitis. It typically manifests between ages 5 and 15. It is a key component of **Hutchinson’s Triad**, which includes: 1. Interstitial Keratitis 2. Hutchinson’s teeth (notched incisors) 3. Sensorineural deafness (8th nerve palsy) In the acute stage, the cornea shows "ground-glass" edema and deep vascularization (the **"Salmon patch"** appearance). In the chronic stage, these vessels regress, leaving behind **"Ghost vessels."** **Why Other Options are Incorrect:** * **Fungal Keratitis:** Characterized by suppurative *ulceration*, feathery margins, and satellite lesions. It involves the epithelium and is not an "interstitial" process. * **Phlyctenular Keratitis:** An allergic nodular inflammation (Type IV hypersensitivity) usually triggered by Tubercular protein. It occurs at the limbus and can lead to a "fascicular ulcer," but it is not a stromal interstitial disease. * **Trachoma:** Primarily affects the conjunctiva and upper tarsal plate, leading to Arlt’s line, Herbert’s pits, and superficial pannus, rather than deep stromal inflammation. **NEET-PG High-Yield Pearls:** * **Unilateral IK:** Most commonly caused by Herpes Simplex Virus (HSV). * **Cogan’s Syndrome:** A rare cause of IK associated with vestibulo-auditory symptoms and systemic vasculitis. * **Wessely Ring:** An immune ring seen in the cornea, often associated with IK or foreign bodies.

Question 308: A patient presents to the OPD with a recent onset of photophobia within 24 hours and a sloughing corneal ulcer. There is a greenish ulcer base. Which of the following can be the causative organism?

A. Acanthamoeba
B. Nocardia
C. Pseudomonas (Correct Answer)
D. Herpes

Explanation: **Explanation:** The clinical presentation of a rapidly progressing, sloughing corneal ulcer with a characteristic **greenish-yellow discharge** or base is a classic hallmark of **Pseudomonas aeruginosa** keratitis. **1. Why Pseudomonas is correct:** Pseudomonas is a Gram-negative aerobe known for its high virulence. It produces enzymes like **proteases and elastases** that cause rapid liquefactive necrosis of the corneal stroma (sloughing). The distinctive greenish hue is due to the production of pigments, primarily **pyocyanin**. It is the most common cause of corneal ulcers in contact lens wearers and can lead to corneal perforation within 24–48 hours if not treated aggressively. **2. Why other options are incorrect:** * **Acanthamoeba:** Typically presents with a **ring-shaped infiltrate** and pain out of proportion to clinical findings. It has a much more chronic, indolent course compared to the rapid onset described here. * **Nocardia:** Usually presents with a "wreath-like" or **patchy infiltrate** and is often associated with trauma involving soil or post-LASIK infections. It does not produce a greenish slough. * **Herpes (HSV):** Characterized by **dendritic ulcers** (with terminal bulbs) and decreased corneal sensations. It does not cause a purulent, sloughing greenish ulcer. **Clinical Pearls for NEET-PG:** * **Pseudomonas:** Rapidly spreading, greenish discharge, common in contact lens users. * **Staphylococcus aureus:** Localized, round/oval ulcer with clear margins. * **Streptococcus pneumoniae:** Often associated with chronic dacryocystitis; causes a "hypopyon ulcer" (Ulcus Serpens). * **Fungal Keratitis:** Feathery margins, satellite lesions, and a dry, leathery appearance.

Question 309: A patient presents with a painless ulcer in the eye. On examination, a long, branching ulcer with desquamated epithelium is seen on the cornea. What is the most likely diagnosis?

A. Bacterial corneal ulcer
B. Neurotrophic ulcer (Correct Answer)
C. Fungal ulcer
D. Dendritic ulcer

Explanation: ***Neurotrophic ulcer***- The defining feature of a **neurotrophic ulcer** is the **painless** nature of the epithelial defect, resulting from damage to the **trigeminal nerve** (CN V1) leading to loss of corneal sensation.- The ulcer morphology, described as a persistent epithelial defect (ulcer) with a desquamated, **geographic** or long-branching appearance, is characteristic of the poor healing seen in the setting of chronic denervation.*Fungal ulcer*- Fungal ulcers typically cause marked pain, photophobia, and conjunctival injection, which contrasts sharply with the painless presentation in this patient.- Morphologically, they are often characterized by elevated, gray-white ulcers with **feathery borders** and commonly exhibit satellite lesions or an underlying **immune ring**.*Dendritic ulcer*- A **dendritic ulcer** is pathognomonic for **Herpes Simplex Virus (HSV) keratitis** and is usually associated with significant pain and foreign body sensation.- While it is branching, it stains vividly, and its key features are **terminal bulbs** at the ends of the branches, differentiating it from the desquamated, geographic type of defect seen in neurotrophic disease.*Bacterial corneal ulcer*- Bacterial corneal ulcers are extremely painful, rapidly progressive, and associated with profound inflammation, ciliary injection, and often significant **anterior chamber reaction (hypopyon)**.- They usually present as dense, whitish-yellow **stromal infiltrates** with an overlying epithelial defect, not a painless, superficially desquamated pattern.

Question 310: Which condition is treated using an Intacs ring, as shown in the image?

A. Keratoconus (Correct Answer)
B. Glaucoma
C. Cataract
D. Corneal ulcer

Explanation: ***Keratoconus*** - The image displays **Intacs**, which are intracorneal ring segments specifically designed to treat **keratoconus** by flattening the steep cornea. - This procedure provides structural support to the weakened, cone-shaped cornea, thereby improving uncorrected and best-corrected visual acuity by reducing **myopia** and **astigmatism**. *Cataract* - Cataract treatment involves the surgical removal of the opacified natural lens, typically through **phacoemulsification**. - An **intraocular lens (IOL)** is implanted in place of the natural lens, not a ring within the corneal stroma as shown. *Corneal ulcer* - A corneal ulcer is an active infection of the cornea and is treated primarily with intensive **topical antimicrobial** therapy (antibiotics, antifungals, or antivirals). - Placing a foreign body like an Intacs ring is contraindicated in an active infection and would worsen the condition. *Glaucoma* - The goal of glaucoma treatment is to lower **intraocular pressure (IOP)** to prevent optic nerve damage. - This is managed with medications (eye drops), **laser procedures** (e.g., trabeculoplasty), or **filtration surgery** (e.g., trabeculectomy), none of which involve corneal ring implants.

Practice by Chapter

Corneal Anatomy and Physiology

Practice Questions

Bacterial Keratitis

Practice Questions

Viral Keratitis

Practice Questions

Fungal Keratitis

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Protozoan Keratitis

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Corneal Degenerations

Practice Questions

Corneal Dystrophies

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Keratoconus and Ectatic Disorders

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Corneal Transplantation

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Corneal Topography and Imaging

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Dry Eye Disease

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Corneal Trauma

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