Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 261: Which of the following is not an association for Keratoconus?

A. Marfan syndrome
B. Leber congenital amaurosis
C. Vernal keratoconjunctivitis
D. Senile cataract (Correct Answer)

Explanation: **Explanation:** Keratoconus is a progressive, non-inflammatory thinning and ectasia of the cornea, leading to irregular astigmatism. It is frequently associated with systemic connective tissue disorders and conditions that involve chronic eye rubbing. **Why Senile Cataract is the correct answer:** Senile cataract is an age-related degenerative change of the crystalline lens. There is no pathophysiological link between the development of keratoconus (which typically manifests in puberty or early adulthood) and senile cataracts (which occur in the elderly). While a patient with keratoconus will eventually age and develop cataracts, it is not considered a clinical "association" or risk factor. **Analysis of Incorrect Options:** * **Marfan Syndrome:** This is a systemic connective tissue disorder (Fibrillin-1 mutation). The structural weakness in the collagen matrix of the cornea in these patients predisposes them to keratoconus. * **Leber Congenital Amaurosis (LCA):** Patients with LCA often have poor vision from birth and frequently perform the **"Oculodigital sign"** (poking/rubbing eyes to stimulate the retina). Chronic mechanical trauma from eye rubbing is a major risk factor for keratoconus. * **Vernal Keratoconjunctivitis (VKC):** This is a severe allergic condition. The intense itching leads to vigorous, chronic eye rubbing, which is the primary mechanism linking VKC to the development of keratoconus. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Associations:** "MR. T" (Down's, Marfan's, Retinitis pigmentosa, Atopic dermatitis, Turner syndrome). * **Early Sign:** Fleischer’s ring (iron deposition at the base of the cone). * **Late Sign:** Munson’s sign (indentation of the lower lid on downgaze). * **Acute Hydrops:** Caused by a rupture in **Descemet’s membrane**, leading to sudden corneal edema. * **Treatment of Choice (Early):** C3R (Corneal Collagen Cross-linking with Riboflavin) to stop progression.

Question 262: What is the recommended time frame for performing a corneal transplant after death?

A. Within 1 hour of death
B. Within 2 hours of death (Correct Answer)
C. Within 30 minutes of death
D. Within 5 hours of death

Explanation: **Explanation:** The viability of corneal tissue is highly dependent on the health of the **corneal endothelium**, which does not regenerate. To ensure a successful transplant (Keratoplasty), the donor eyes must be harvested as soon as possible to prevent autolysis and exposure-related damage. * **Why Option B is Correct:** In ideal clinical practice, the recommended time frame for enucleation (removal of the eye) or in-situ corneal excision is **within 2 hours of death**. This minimizes the risk of endothelial cell loss and ensures the graft remains clear after surgery. While harvesting can technically be performed up to 6 hours post-mortem (especially if the body is refrigerated), the "ideal" or "recommended" standard taught for competitive exams like NEET-PG is 2 hours. * **Why Options A & C are Incorrect:** While harvesting within 30 minutes or 1 hour would provide excellent tissue, it is logistically impractical in most clinical settings. These time frames are not the standard recommendation. * **Why Option D is Incorrect:** By 5 hours, significant epithelial sloughing and endothelial degradation may have begun, especially if the cadaver was kept at room temperature. While 6 hours is often cited as the *upper limit*, it is not the *recommended* ideal window. **High-Yield Clinical Pearls for NEET-PG:** * **Storage Media:** Short-term (48 hours) in **MK Medium**; Intermediate (up to 2 weeks) in **Optisol-GS** (most common); Long-term (months) via **Cryopreservation**. * **Age Limit:** Donor age is ideally between 2 to 70 years. * **Contraindications for Donation:** Death of unknown cause, HIV, Hepatitis B/C, Rabies, Syphilis, Leukemia, and Creutzfeldt-Jakob disease. * **Endothelial Count:** A donor cornea is generally considered suitable for transplant if the endothelial cell count is **>2000 cells/mm²**.

Question 263: Disciform herpetic keratitis involves which layer of the cornea?

A. Epithelium
B. Descemet's membrane
C. Endothelium (Correct Answer)
D. Basement membrane

Explanation: **Explanation:** **Disciform Keratitis** is a type of **Endotheliitis** caused by a delayed-type hypersensitivity reaction (Type IV) to the Herpes Simplex Virus (HSV) antigen. 1. **Why Endothelium is correct:** In disciform keratitis, the primary site of inflammation is the **corneal endothelium**. The inflammatory process leads to endothelial pump failure, resulting in localized, disc-shaped stromal edema. A hallmark clinical finding is the presence of **Keratic Precipitates (KPs)** directly underlying the area of edema, signifying endothelial involvement. 2. **Why other options are incorrect:** * **Epithelium:** Epithelial involvement is characteristic of *Dendritic* or *Geographic* ulcers (active viral replication), not disciform keratitis. * **Descemet’s Membrane:** While it may show folds (striate keratopathy) due to overlying edema, it is a basement membrane and not the primary site of the immunological trigger. * **Basement Membrane:** This layer is involved in epithelial adhesion; damage here leads to recurrent epithelial erosions, not the deep stromal edema seen in disciform disease. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Central/paracentral disc-shaped stromal edema, KPs, and often increased Intraocular Pressure (IOP). * **Wessely Ring:** An immune ring of stromal precipitation may sometimes be seen surrounding the edema. * **Sensation:** Corneal sensations are typically **diminished or absent** (a classic HSV feature). * **Management:** Unlike epithelial herpes (where steroids are contraindicated), Disciform Keratitis is treated with **topical steroids** to dampen the immune response, always covered by **prophylactic topical antivirals** (e.g., Ganciclovir/Acyclovir) to prevent viral reactivation.

Question 264: Which of the following is NOT true about herpetic keratitis?

A. Stromal Keratitis
B. Dendritic Ulcer
C. Corneal guttata (Correct Answer)
D. Disciform Keratitis

Explanation: **Explanation:** Herpetic keratitis is caused by the **Herpes Simplex Virus (HSV)** and is a leading cause of corneal blindness. It typically presents in various clinical forms depending on whether the infection is an active viral replication (epithelial) or an immune-mediated response (stromal/endothelial). **Why "Corneal Guttata" is the correct answer:** Corneal guttata refers to drop-like collagenous deposits on the Descemet membrane, representing focal dysfunction of the corneal endothelial cells. This is the hallmark clinical sign of **Fuchs’ Endothelial Corneal Dystrophy (FECD)**, a genetic degenerative condition. It is not caused by viral infections like HSV. **Analysis of incorrect options:** * **Dendritic Ulcer:** This is the most characteristic presentation of **Epithelial Keratitis**. It features a linear, branching ulcer with "terminal bulbs" that stain brightly with fluorescein. * **Stromal Keratitis:** This occurs due to an immune-mediated response to viral antigens. It can present as *Interstitial Keratitis* (infiltrates and vascularization) or *Necrotizing Stromal Keratitis* (direct viral invasion leading to necrosis/perforation). * **Disciform Keratitis:** This is a form of **Endotheliitis**. It presents as a central, disc-shaped area of stromal edema without significant infiltration, caused by a delayed hypersensitivity reaction to the virus. **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** Dendritic ulcers stain with **Fluorescein** (base of the ulcer) and **Rose Bengal** (devitalized cells at the margins). * **Sensation:** A key diagnostic feature of herpetic keratitis is **decreased corneal sensations** (hypoesthesia). * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir is the drug of choice for epithelial disease. **Steroids** are strictly contraindicated in dendritic ulcers but are the mainstay of treatment for Disciform Keratitis (always used under antibiotic/antiviral cover).

Question 265: Which of the following fungal infections most commonly causes corneal ulcers?

A. Trichophyton
B. Aspergillus (Correct Answer)
C. Mucor
D. Sporothrix

Explanation: **Explanation:** **Aspergillus** is the most common cause of fungal keratitis (corneal ulcers) worldwide, particularly in tropical and subtropical regions like India. Fungal ulcers typically occur following **vegetative trauma** (e.g., injury with a branch, leaf, or agricultural product). Aspergillus species are ubiquitous filamentous fungi that easily invade the corneal stroma, often leading to a characteristic "dry," grayish-white infiltrate with feathery margins. **Analysis of Incorrect Options:** * **Trichophyton:** This is a dermatophyte primarily responsible for superficial skin, hair, and nail infections (Tinea). It rarely involves the cornea. * **Mucor:** While Mucor can cause devastating **Rhino-oculo-cerebral mucormycosis** (especially in uncontrolled diabetics), it typically presents as an invasive orbital cellulitis rather than a primary corneal ulcer. * **Sporothrix:** This causes Sporotrichosis ("Rose gardener’s disease"), which usually presents as chronic granulomatous nodules along lymphatic channels. Ocular involvement is rare and usually affects the conjunctiva or lacrimal apparatus. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause in India:** *Aspergillus* is the overall leader, though *Fusarium* is also highly prevalent in southern regions. * **Most common cause in temperate climates/USA:** *Candida* (yeast). * **Clinical Signs:** Look for **feathery margins**, **satellite lesions**, and a **fixed hypopyon** (which does not shift with head position due to its thick, fibrinous nature). * **Diagnosis:** Gold standard is corneal scraping for **KOH mount** (shows hyphae) and culture on **Sabouraud’s Dextrose Agar (SDA)**. * **Treatment:** Topical **Natamycin (5%)** is the drug of choice for filamentous fungi like Aspergillus.

Question 266: Which of the following type of corneal degeneration is associated with formation of drop-like excrescences of hyaline material which project into the anterior chamber around the corneal periphery?

A. Vogt's limbal girdle
B. Hassall-Henle bodies (Correct Answer)
C. Lipoid keratopathy
D. Hyaline degeneration

Explanation: ### Explanation **Correct Answer: B. Hassall-Henle bodies** **Hassall-Henle bodies** are a physiological age-related change characterized by the formation of small, drop-like excrescences of hyaline material. These represent focal thickenings of the **Descemet’s membrane** that project into the anterior chamber. Crucially, they are located in the **corneal periphery**. While they are histologically identical to "Guttata," the term Hassall-Henle bodies is reserved for these peripheral changes seen in normal aging, whereas central guttata are characteristic of Fuchs' endothelial dystrophy. **Analysis of Incorrect Options:** * **A. Vogt's limbal girdle:** This is a common, benign, age-related degeneration appearing as narrow, crescentic white lines in the interpalpebral area of the peripheral cornea (nasal and temporal). It involves subepithelial elastotic degeneration, not Descemet’s membrane. * **C. Lipoid keratopathy:** This involves the deposition of lipids (cholesterol, lecithin) in the corneal stroma. It can be primary or secondary (following vascularization due to trauma or keratitis) and presents as opaque, yellowish-white deposits. * **D. Hyaline degeneration:** This is a broad term often associated with Salzmann’s nodular degeneration or Spheroidal degeneration. It involves the replacement of Bowman’s membrane and superficial stroma with hyaline material, but it does not project from the Descemet’s membrane into the anterior chamber. **High-Yield Clinical Pearls for NEET-PG:** * **Hassall-Henle bodies = Peripheral** (Normal aging). * **Corneal Guttata = Central** (Pathological; hallmark of Fuchs' Endothelial Corneal Dystrophy). * Both appear as "beaten silver" or "orange peel" appearances on specular microscopy. * **Arcus Senilis** is the most common peripheral corneal degeneration, involving lipid deposition starting at the superior and inferior poles.

Question 267: A 62-year-old woman with keratoconjunctivitis sicca is most likely to demonstrate corneal staining in which location?

A. Superior third
B. Middle third (interpalpebral) (Correct Answer)
C. Inferior third
D. Diffuse over entire cornea

Explanation: ### Explanation **Correct Answer: B. Middle third (interpalpebral)** **Medical Concept:** Keratoconjunctivitis sicca (KCS), commonly known as dry eye syndrome, occurs due to a deficiency in tear production or excessive evaporation. In a normal physiological state, the **interpalpebral zone** (the area of the eyeball exposed between the upper and lower eyelids when the eyes are open) is the most vulnerable to environmental desiccation. Because this middle third of the cornea and conjunctiva lacks the constant protection of the eyelids and experiences the highest rate of tear film evaporation, it is the primary site for epithelial breakdown. On fluorescein or Rose Bengal staining, this manifests as punctate erosions localized to the interpalpebral area. **Analysis of Incorrect Options:** * **A. Superior third:** Staining in the superior cornea is typically associated with **Superior Limbic Keratoconjunctivitis (SLK)** or mechanical irritation from the upper tarsal conjunctiva (e.g., vernal keratoconjunctivitis or floppy eyelid syndrome). * **C. Inferior third:** Staining in the lower third is characteristic of **exposure keratopathy** (due to incomplete lid closure/lagophthalmos) or **staphylococcal blepharitis**, where toxins pool along the lower lid margin. * **D. Diffuse:** While severe, end-stage dry eye can involve the whole cornea, the *most likely* and classic presentation of KCS is localized to the interpalpebral region. Diffuse staining is more common in chemical injuries or severe viral keratitis. **NEET-PG High-Yield Pearls:** * **Schirmer’s Test I:** Measures total secretion (normal >15mm in 5 mins; <5mm is diagnostic for KCS). * **Rose Bengal/Lissamine Green:** Best stains for identifying devitalized epithelial cells in dry eye. * **Sjögren’s Syndrome:** The triad of dry eyes, dry mouth (xerostomia), and rheumatoid arthritis (or other connective tissue disease). * **Tear Film Break-up Time (TBUT):** Normal is 15–35 seconds; <10 seconds indicates tear film instability.

Question 268: Which of the following is NOT a cause of enlarged corneal nerves?

A. Neurofibromatosis
B. Riley-Day dysautonomia
C. Multiple endocrine neoplasia (MEN)
D. Band-shaped keratopathy (Correct Answer)

Explanation: **Explanation:** The presence of thickened or prominent corneal nerves is a specific clinical sign observed during slit-lamp examination. This occurs due to the proliferation of Schwann cells or the accumulation of abnormal materials within the nerve sheaths. **Why Band-shaped Keratopathy (BSK) is the correct answer:** Band-shaped keratopathy is a degenerative condition characterized by the deposition of **calcium salts (hydroxyapatite)** in the subepithelial layers, specifically the Bowman’s membrane. It is associated with chronic intraocular inflammation (e.g., Uveitis), hypercalcemia, or silicone oil in the anterior chamber. It does **not** involve the corneal nerves; rather, it presents as a horizontal "Swiss-cheese" pattern of calcification across the interpalpebral fissure. **Analysis of Incorrect Options (Causes of Enlarged Corneal Nerves):** * **Neurofibromatosis (Type 1):** A classic cause where nerve sheath tumors (neurofibromas) and thickened nerves occur throughout the body, including the cornea. * **Riley-Day Dysautonomia (Hereditary Sensory and Autonomic Neuropathy Type III):** Characterized by a lack of fungiform papillae on the tongue and prominent corneal nerves, often leading to neurotrophic keratitis. * **Multiple Endocrine Neoplasia (MEN Type 2B):** This is a high-yield association. Patients present with medullary carcinoma of the thyroid, pheochromocytoma, and mucosal neuromas. Thickened corneal nerves are a hallmark ocular finding. **NEET-PG Clinical Pearls:** To remember the causes of enlarged corneal nerves, use the mnemonic **"MEN CAN"**: * **M:** **M**EN Type 2B, **M**edullary carcinoma of thyroid * **E:** **E**dema (Corneal hydrops in Keratoconus) * **N:** **N**eurofibromatosis, **N**eoplasia * **C:** **C**ongenital Glaucoma * **A:** **A**canthamoeba keratitis (Radial keratoneuritis—highly painful) * **N:** **N**eoplasia / **N**oonan Syndrome / **N**euroleprosy (rarely)

Question 269: Acanthamoeba keratitis is associated with which of the following?

A. Allergic reaction to tuberculoprotein
B. Contact lens usage (Correct Answer)
C. Lesion of herpes zoster
D. Congenital syphilis

Explanation: **Explanation:** **Acanthamoeba keratitis** is a rare but vision-threatening parasitic infection caused by free-living amoebae found in soil and water. **Why Contact Lens Usage is Correct:** The strongest risk factor for Acanthamoeba keratitis (seen in over 80% of cases) is **contact lens usage**, particularly when associated with poor hygiene. This includes using tap water to rinse lenses, swimming/showering while wearing lenses, or using contaminated homemade saline solutions. The parasite adheres to the contact lens surface and subsequently invades the corneal epithelium, often facilitated by minor micro-trauma from lens wear. **Analysis of Incorrect Options:** * **A. Allergic reaction to tuberculoprotein:** This describes **Phlyctenular keratoconjunctivitis**, a type IV hypersensitivity reaction to endogenous bacterial antigens (most commonly *M. tuberculosis* or *Staphylococcus*). * **C. Lesion of herpes zoster:** This refers to **Herpes Zoster Ophthalmicus (HZO)**, caused by the reactivation of the Varicella-Zoster virus in the trigeminal ganglion. * **D. Congenital syphilis:** This is classically associated with **Interstitial Keratitis**, often presenting as part of Hutchinson’s triad (interstitial keratitis, sensorineural deafness, and notched incisors). **High-Yield Clinical Pearls for NEET-PG:** * **Classic Presentation:** Severe, excruciating pain that is **disproportionate** to the clinical signs. * **Pathognomonic Sign:** **Radial Keratoneuritis** (infiltration around corneal nerves). * **Late Stage:** A characteristic **Ring Infiltrate** may form. * **Diagnosis:** Confirmed by **non-nutrient agar with E. coli overlay** or Calcofluor white stain. * **Treatment:** Topical biguanides (PHMB) or diamidines (Propamidine/Brolene).

Question 270: Which topical antifungal is used in corneal fungal infections?

A. Silver sulfadiazine
B. Neomycin
C. Natamycin (Correct Answer)
D. Griseofulvin

Explanation: **Explanation:** **Natamycin** is the drug of choice for the topical treatment of filamentous fungal keratitis (e.g., *Aspergillus* and *Fusarium*). It belongs to the **polyene** class of antifungals. Its mechanism of action involves binding to fungal cell membrane ergosterol, leading to increased membrane permeability and cell death. It is the only FDA-approved topical ophthalmic antifungal and is particularly effective because it adheres well to the corneal surface, providing sustained therapeutic levels. **Analysis of Incorrect Options:** * **Silver sulfadiazine (A):** While it has some antifungal properties and is used in burn dressings, it is not a standard topical treatment for fungal keratitis in clinical practice. * **Neomycin (B):** This is an aminoglycoside **antibiotic** used to treat bacterial infections. It has no activity against fungi. * **Griseofulvin (D):** This is an **oral** antifungal primarily used for dermatophytosis (skin/hair/nail infections). It is not used topically and is ineffective against the common pathogens causing fungal keratitis. **High-Yield Clinical Pearls for NEET-PG:** * **Filamentous Fungi (Aspergillus/Fusarium):** Most common cause of fungal keratitis in India (often following trauma with vegetative matter). **Natamycin 5%** is the first-line treatment. * **Yeasts (Candida):** More common in pre-existing ocular surface disease. **Amphotericin B (0.15%)** is the preferred topical treatment. * **Clinical Sign:** Fungal ulcers typically present with "feathery borders," "satellite lesions," and an "immune ring" (Wessely ring). * **Contraindication:** Topical steroids are strictly contraindicated in fungal keratitis as they worsen the infection.

Practice by Chapter

Corneal Anatomy and Physiology

Practice Questions

Bacterial Keratitis

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Viral Keratitis

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Fungal Keratitis

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Protozoan Keratitis

Practice Questions

Corneal Degenerations

Practice Questions

Corneal Dystrophies

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Keratoconus and Ectatic Disorders

Practice Questions

Corneal Transplantation

Practice Questions

Corneal Topography and Imaging

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Dry Eye Disease

Practice Questions

Corneal Trauma

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