Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 381: What is the dye and filter used to diagnose corneal ulcers?

A. Lissamine green dye - visualized under green filter
B. Lissamine blue dye - visualized under cobalt blue filter
C. Fluorescein dye - visualized under green filter
D. Fluorescein dye - visualized under cobalt blue filter (Correct Answer)

Explanation: ***Fluorescein dye - visualized under cobalt blue filter*** - **Fluorescein dye** is applied to the eye, and it stains areas of **epithelial defects**, such as those found in corneal ulcers, appearing bright green. - The **cobalt blue filter** enhances the visibility and fluorescence of the stained areas, making corneal ulcers clearly discernible. *Lissamine green dye - visualized under green filter* - **Lissamine green** is used to identify **devitalized cells** and **mucous filaments** on the ocular surface, rather than primary corneal epithelial defects. - It is visualized under **white light or red-free filter**, not a green filter, and is less suitable for diagnosing corneal ulcers directly. *Lissamine blue dye - visualized under cobalt blue filter* - This option refers to a non-existent dye combination for routine corneal ulcer diagnosis. **Lissamine blue** is not a standard ophthalmic dye for this purpose. - While a cobalt blue filter is used with fluorescein, it is not paired with a "Lissamine blue dye." *Fluorescein dye - visualized under green filter* - **Fluorescein dye** is indeed the correct dye for diagnosing corneal ulcers by staining epithelial defects. - However, it is visualized under a **cobalt blue filter**, not a green filter, to maximize fluorescence and contrast.

Question 382: What is a characteristic finding in fungal corneal ulcers?

A. Satellite lesions (Correct Answer)
B. Dendritic ulcer
C. Ring abscess
D. White hypopyon

Explanation: ***Satellite lesions*** - **Fungal corneal ulcers** often present with characteristic **satellite lesions**, which are smaller, adjacent infiltrates surrounding the main ulcer. - These lesions indicate the spread of fungal hyphae into the surrounding corneal stroma. - This is the **most characteristic feature** that helps distinguish fungal from bacterial keratitis. *Dendritic ulcer* - A **dendritic ulcer** is pathognomonic for **herpes simplex keratitis**, not fungal infections. - It presents as a branching, tree-like epithelial defect, which is distinct from the appearance of fungal ulcers. *Ring abscess* - A **ring abscess** is more commonly associated with **Acanthamoeba keratitis** or severe bacterial infections. - While it can occur in very advanced fungal infections, it is not a characteristic initial finding. *White hypopyon* - While fungal keratitis can present with a **white, fluffy hypopyon**, this is not specific enough to be the most characteristic finding. - Hypopyon indicates severe inflammation and can be seen in bacterial, fungal, and other severe corneal infections. - The presence of **satellite lesions** remains the key distinguishing feature for fungal etiology.

Question 383: Kayser-Fleischer rings (KF rings) are seen in:

A. Pterygium
B. Hemochromatosis
C. Wilson's disease (Correct Answer)
D. Menke's kinked hair syndrome

Explanation: ***Wilson's disease*** - **Kayser-Fleischer (KF) rings** are pathognomonic for **Wilson's disease**, resulting from **copper deposition** in the Descemet's membrane of the cornea. - This genetic disorder leads to excessive **copper accumulation** in the liver, brain, and other tissues due to impaired copper excretion. *Pterygium* - A **pterygium** is a benign growth of the **conjunctiva** that extends onto the cornea, typically appearing as a fleshy, triangular lesion. - It is not associated with systemic copper metabolism disorders or the presence of KF rings. *Hemochromatosis* - **Hemochromatosis** is a disorder of **iron overload**, leading to iron deposition in various organs, including the liver, heart, and pancreas. - It does not involve copper metabolism or the formation of corneal rings. *Menke's kinked hair syndrome* - **Menke's syndrome** is a genetic disorder characterized by **copper deficiency**, leading to impaired copper transport and utilization. - It presents with severe neurological deterioration, connective tissue abnormalities, and characteristic **kinky hair**, but not KF rings.

Question 384: Which organism can penetrate corneal endothelium?

A. Staphylococcus Aureus
B. Haemophilus influenzae (Correct Answer)
C. Aspergillus fumigatus
D. Neisseria gonorrhoeae

Explanation: ***Haemophilus influenzae*** - *Haemophilus influenzae* is unique in its ability to penetrate the **intact corneal endothelium** through its specific virulence factors and enzymatic mechanisms. - Along with *Neisseria meningitidis*, it can breach the **Descemet's membrane and endothelial barrier** without requiring prior epithelial damage. - This property makes it particularly dangerous as it can cause **endophthalmitis** by directly accessing the anterior chamber. *Neisseria gonorrhoeae* - While highly virulent, *N. gonorrhoeae* penetrates the **corneal epithelium** (outer layer) through its proteases, not the endothelium (inner layer). - It causes severe **hyperacute conjunctivitis** and can lead to **corneal perforation**, but via epithelial destruction and stromal infiltration. *Staphylococcus aureus* - A common cause of **bacterial keratitis** following epithelial defects or trauma. - Causes stromal infiltration and abscess formation but **cannot penetrate intact endothelium**. *Aspergillus fumigatus* - This fungus causes **fungal keratitis** typically after trauma with vegetative matter. - Invades through **epithelial breaches** and stromal infiltration, not through intact endothelial penetration.

Question 385: All of the following are true about Keratoconus, except:

A. Astigmatism
B. Increased curvature of cornea and Astigmatism
C. Thick cornea (Correct Answer)
D. Fleischer's ring

Explanation: ***Thick cornea*** - Keratoconus is characterized by **progressive corneal thinning** and weakening, not thickening. - This corneal thinning leads to a conical protrusion, causing significant visual distortion and irregular astigmatism. *Increased curvature of cornea and Astigmatism* - Keratoconus features **increased corneal curvature** with progressive steepening into a cone-shaped configuration. - This results in **irregular astigmatism**, a hallmark feature causing distorted vision at all distances. *Astigmatism* - **Irregular astigmatism** is a cardinal feature of keratoconus due to the asymmetric corneal shape. - Causes blurred and distorted vision that is difficult to correct with spectacles alone. *Fleischer's ring* - **Fleischer's ring** is an iron deposit ring at the base of the cone in keratoconus, visible on slit-lamp examination. - It represents hemosiderin deposition in the basal epithelial cells and is a characteristic clinical sign of keratoconus.

Question 386: Descemet membrane breach is seen in ?

A. Angle closure glaucoma
B. Acute Iridocyclitis
C. Subconjunctival hemorrhage
D. Congenital glaucoma (Buphthalmos) (Correct Answer)

Explanation: ***Congenital glaucoma (Buphthalmos)*** - In **congenital glaucoma**, increased intraocular pressure (IOP) in infancy stretches the developing eye, leading to enlargement (buphthalmos) and **Descemet membrane breaches** or ruptures. - These ruptures appear as fine, parallel, or branching lines on the posterior corneal surface, known as **Haab's striae**, which are characteristic signs of this condition. *Angle closure glaucoma* - This condition involves a sudden rise in IOP due to physical obstruction of the **aqueous humor outflow** and does not typically cause Descemet membrane breaks. - Clinical signs include **corneal edema** due to endothelial dysfunction, but not membrane breaches. *Acute Iridocyclitis* - **Acute iridocyclitis** is an inflammatory condition of the iris and ciliary body, primarily causing cells and flare in the anterior chamber. - It does not directly lead to **Descemet membrane breaches** or structural damage like stretching of the cornea. *Subconjunctival hemorrhage* - This condition is characterized by **bleeding under the conjunctiva** and is typically due to ruptured conjunctival blood vessels. - It is a superficial condition that does not involve the cornea or the Descemet membrane.

Question 387: Kayser-Fleischer ring is found in which layer of cornea?

A. Endothelium
B. Descemet's membrane (Correct Answer)
C. Bowman's layer
D. Corneal stroma

Explanation: ***Descemet's membrane*** - Kayser-Fleischer rings are caused by **copper deposition** at the periphery of the cornea, specifically within **Descemet's membrane**. - This membrane is located between the **corneal stroma** and the **endothelium**. *Bowman's layer* - Bowman's layer is a thin, acellular layer of the cornea that lies beneath the **corneal epithelium**. - While it plays a role in corneal integrity, it is not the site of **copper deposition** in Wilson's disease. *Corneal stroma* - The corneal stroma is the thickest layer of the cornea, composed primarily of **collagen fibrils**. - Although it contains most of the corneal mass, **copper deposition** in Kayser-Fleischer rings does not specifically occur within the main stromal layer. *Endothelium* - The corneal endothelium is the innermost layer of the cornea, responsible for maintaining **corneal deturgescence**. - While it is adjacent to Descemet's membrane, the copper rings are deposited in the membrane itself, not directly in the endothelial cell layer.

Question 388: Which of the following is NOT a cause of crystal keratopathy?

A. Schnyder's Dystrophy
B. Bietti's Dystrophy
C. Diabetes (Correct Answer)
D. Cystinosis

Explanation: ***Diabetes*** - While diabetes can cause various ocular complications, such as **diabetic retinopathy**, **neovascular glaucoma**, and **cataracts**, it is **not associated** with crystal keratopathy. - Corneal changes in diabetes might include epithelial defects or reduced corneal sensitivity, but **not the deposition of crystalline substances in the cornea**. - **This is the correct answer** as diabetes does NOT cause crystal keratopathy. *Cystinosis* - **Cystinosis** is a metabolic disorder characterized by the accumulation of **cystine crystals** throughout the body, including the **cornea**. - These crystals can lead to significant **photophobia**, **corneal erosions**, and visual impairment, making it a **classic cause of crystal keratopathy**. - Corneal involvement typically appears in childhood with diffuse crystalline deposits. *Schnyder's Dystrophy* - **Schnyder's corneal dystrophy** is an inherited corneal dystrophy characterized by the deposition of **cholesterol and lipid crystals** in the central and peripheral cornea. - This leads to **dense corneal opacification** and can significantly impair vision over time, representing a **classic cause of crystal keratopathy**. - The cornea shows characteristic subepithelial and stromal crystal deposits. *Bietti's Crystalline Dystrophy* - **Bietti's crystalline dystrophy** is a rare, inherited chorioretinal dystrophy characterized by **crystalline deposits primarily in the retina and choroid**. - While the name suggests crystalline involvement, these crystals are predominantly **intraretinal and do NOT typically cause corneal crystal deposits**. - Therefore, Bietti's is **NOT a typical cause of crystal keratopathy** (corneal disease), though minimal peripheral corneal crystals have been rarely reported in advanced cases. - The confusion arises from the word "crystalline" in its name, but the pathology is retinal, not corneal.

Question 389: All are true regarding cornea except:

A. The cornea is richly vascular. (Correct Answer)
B. Endothelium help in maintaining dehydrated state
C. Oxygen is mostly derived by epithelium directly from the air through tear film
D. Corneal thickness is greater at periphery than center

Explanation: ***The cornea is richly vascular.*** - The cornea is an **avascular** tissue, meaning it lacks blood vessels, which is crucial for its transparency. - This avascularity helps prevent light scatter and maintains clear vision. - The cornea receives nutrition from the **aqueous humor**, **tear film**, and **limbal blood vessels** through diffusion. *Endothelium help in maintaining dehydrated state* - The **corneal endothelium** actively pumps fluid out of the corneal stroma via **Na-K-ATPase pumps**, preventing swelling and maintaining its relative state of dehydration. - This **deturgescence** is essential for the cornea's transparency and optimal refractive power. *Oxygen is mostly derived by epithelium directly from the air through tear film* - The corneal **epithelium** primarily obtains oxygen directly from the atmosphere via the **tear film** when the eyes are open. - During sleep, oxygen is primarily supplied by the **palpebral conjunctival vessels**. *Corneal thickness is greater at periphery than center* - The cornea is **thinner at the center** (around 520-540 µm) and gradually **thicker towards the periphery** (around 600-640 µm). - This structural difference contributes to its optical properties and mechanical stability.

Question 390: Which of the following statements about Fuchs' corneal dystrophy is incorrect?

A. Endothelial dystrophy
B. Occurs in old age
C. Unilateral condition (Correct Answer)
D. Posterior dystrophy

Explanation: ***Unilateral condition - INCORRECT STATEMENT*** - **Fuchs' corneal dystrophy** is typically a **bilateral condition**, although it can be asymmetric in its presentation. - The disease often affects both eyes, progressing from early morning blurriness to constant visual impairment. - This is the INCORRECT statement - Fuchs' is NOT unilateral. *Posterior dystrophy - Correct statement* - **Fuchs' corneal dystrophy** is classified as a posterior corneal dystrophy, meaning it primarily affects the **corneal endothelium** and Descemet's membrane. - This posterior involvement leads to the characteristic guttata and corneal edema. *Endothelial dystrophy - Correct statement* - It is fundamentally an **endothelial dystrophy**, resulting from primary dysfunction and loss of corneal endothelial cells. - The compromised endothelial pump function leads to **stromal edema** and reduced visual acuity. *Occurs in old age - Correct statement* - Fuchs' corneal dystrophy typically presents in **middle to old age**, with symptoms often becoming noticeable in individuals over 50. - While congenital forms of corneal dystrophy exist, Fuchs' is not usually one of them.

Practice by Chapter

Corneal Anatomy and Physiology

Practice Questions

Bacterial Keratitis

Practice Questions

Viral Keratitis

Practice Questions

Fungal Keratitis

Practice Questions

Protozoan Keratitis

Practice Questions

Corneal Degenerations

Practice Questions

Corneal Dystrophies

Practice Questions

Keratoconus and Ectatic Disorders

Practice Questions

Corneal Transplantation

Practice Questions

Corneal Topography and Imaging

Practice Questions

Dry Eye Disease

Practice Questions

Corneal Trauma

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free