Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 411: Which virus is most commonly associated with disciform keratitis?

A. Rubella Virus
B. Herpes Simplex Virus (HSV) (Correct Answer)
C. Human Immunodeficiency Virus (HIV)
D. Hepatitis B Virus (HBV)

Explanation: ***Herpes Simplex Virus (HSV)*** - **HSV** is the most common cause of **infectious disciform keratitis**, often following a primary ocular HSV infection or reactivation. - Disciform keratitis caused by HSV is a form of **immune-mediated stromal keratitis**, characterized by corneal edema, inflammation, and potential vision loss. *Rubella Virus* - While Rubella can cause ocular manifestations, such as **congenital cataracts** and **glaucoma** in infants, it is not typically associated with disciform keratitis in adults or children. - **Congenital rubella syndrome** is the primary context for ophthalmic issues related to this virus. *Human Immunodeficiency Virus (HIV)* - HIV can lead to various ocular complications, such as **CMV retinitis**, **Kaposi's sarcoma** of the conjunctiva, and **HIV retinopathy**. - However, HIV itself is **not directly linked** to disciform keratitis. *Hepatitis B Virus (HBV)* - HBV infection primarily affects the **liver** and is not commonly associated with direct ocular infections like keratitis. - Ocular manifestations are rare and often nonspecific, mainly related to systemic immune responses rather than direct viral replication in the eye.

Question 412: What is the most common protozoan associated with keratitis?

A. Plasmodium
B. Acanthamoeba (Correct Answer)
C. Toxoplasma
D. Entamoeba histolytica

Explanation: ***Acanthamoeba*** - **Acanthamoeba keratitis** is a serious and painful infection of the eye's cornea, most commonly associated with **contact lens wearers** who do not properly disinfect their lenses. - The organism is a **free-living protozoan** found in soil and water. *Plasmodium* - **Plasmodium** species are the causative agents of **malaria**, a disease that primarily affects **red blood cells** and the liver. - While it can manifest with ocular symptoms like **retinopathy**, it does not typically cause **keratitis**. *Toxoplasma* - **Toxoplasma gondii** causes **toxoplasmosis**, an infection that can lead to **chorioretinitis** (inflammation of the retina and choroid), especially in immunocompromised individuals or congenitally infected infants. - It does not directly cause **keratitis** as its primary ocular manifestation. *Entamoeba histolytica* - **Entamoeba histolytica** is the protozoan responsible for **amebiasis**, particularly **amoebic dysentery** and **liver abscesses**. - Ocular involvement with *Entamoeba histolytica* is extremely rare and typically involves **metastatic lesions** to the orbit or eyelids, not directly primary keratitis.

Question 413: All of the following drugs can result in amorphous whorl-like corneal opacities except:

A. Chloroquine
B. Chlorpromazine (Correct Answer)
C. Amiodarone
D. Indomethacin

Explanation: ***Chlorpromazine*** - Chlorpromazine can cause **corneal and lenticular opacities**, but these are typically **granular, punctate, or stellate in pattern**, NOT amorphous whorl-like opacities. - The deposits are usually **fine, golden-brown pigment granules** in the corneal epithelium and anterior lens capsule, distinctly different from the lipid-based verticillata pattern. - Also associated with **pigmentary retinopathy** in chronic use. *Amiodarone* - **Classic cause of corneal verticillata** (vortex keratopathy) - amorphous, whorl-like opacities radiating from below the corneal center. - Due to **phospholipid accumulation** in corneal epithelial lysosomes. - Present in >90% of patients on long-term therapy; usually **asymptomatic and reversible** on discontinuation. *Chloroquine* - Causes **corneal verticillata** similar to amiodarone, appearing as bilateral whorl-like opacities in the basal epithelium. - Due to **drug-induced lipidosis** with accumulation in corneal epithelial cells. - More commonly known for **bull's eye maculopathy** (retinopathy), but corneal changes occur earlier and are **reversible** upon drug cessation. *Indomethacin* - This NSAID can cause **corneal verticillata** or whorl-like opacities, though less commonly reported than amiodarone or chloroquine. - The corneal deposits are typically **benign and reversible** after discontinuation. - Mechanism involves drug accumulation in corneal epithelium.

Question 414: Topical fluorescein stain is used in the eye to stain?

A. Cornea (Correct Answer)
B. Retina
C. Choroid
D. Iris

Explanation: **Cornea** - Fluorescein staining is primarily used to detect **corneal abrasions**, **ulcers**, or other defects in the corneal epithelium. - The dye stains areas where the **epithelial layer is disrupted**, making them visible under a cobalt blue light. *Retina* - The retina is a light-sensitive layer at the back of the eye and is not directly stained by topical fluorescein. - **Fluorescein angiography**, an invasive procedure where dye is injected intravenously, is used to visualize retinal blood vessels. *Choroid* - The choroid is a vascular layer between the retina and the sclera; it is not directly stained by topical fluorescein. - Its blood flow can be visualized using **indocyanine green angiography**, not topical fluorescein. *Iris* - The iris is the colored part of the eye that controls pupil size and is not stained by topical fluorescein. - While integral to eye function, it does not have the epithelial structure that topical fluorescein is designed to highlight for diagnostic purposes.

Question 415: In xerophthalmia classification, which condition is classified as stage X2?

A. Corneal xerosis (Correct Answer)
B. Bitot's spots
C. Corneal ulceration
D. Corneal scar

Explanation: ***Corneal xerosis*** - **Corneal xerosis** is classified as stage **X2** in the WHO classification of xerophthalmia, indicating pronounced dryness of the cornea. - This stage represents a more advanced form of **vitamin A deficiency** affecting the cornea itself. *Bitot's spots* - **Bitot's spots** are classified as stage **X1B**, which involves conjunctival changes rather than corneal. - They are typically foamy, white patches on the **bulbar conjunctiva**, indicating squamous metaplasia. *Corneal ulceration* - **Corneal ulceration**, also known as **corneal keratomalacia**, is classified as stage **X3A** or **X3B**, depending on its extent. - This stage signifies severe corneal damage and carries a high risk of blindness. *Corneal scar* - **Corneal scar** is classified as stage **XS**, indicating a permanent sequela of previous corneal xerophthalmia. - It represents irreversible damage to the cornea, often leading to significant visual impairment.

Question 416: Krukenberg's spindle seen in patients with pigmentary glaucoma refers to deposition of pigment on

A. Trabecular meshwork
B. Anterior surface of the lens
C. Back of cornea (Correct Answer)
D. Posterior surface of iris

Explanation: ***Back of cornea*** - **Krukenberg's spindle** is a classic sign of **pigment dispersion syndrome** and subsequent pigmentary glaucoma. - It results from the deposition of **pigment granules** on the **endothelium of the central posterior cornea**, forming a **vertical spindle-shaped pattern**. - This is a pathognomonic finding that helps distinguish pigmentary glaucoma from other forms of glaucoma. *Incorrect: Trabecular meshwork* - While **pigment deposition** on the trabecular meshwork is crucial in pigmentary glaucoma, leading to **increased outflow resistance** and elevated intraocular pressure, the term **Krukenberg's spindle** specifically refers to pigment on the corneal endothelium. - Pigment on the trabecular meshwork appears as **increased pigmentation of the angle** on gonioscopy, sometimes described as **Scheie's stripe** or **Sampaolesi's line**. *Incorrect: Anterior surface of the lens* - Pigment can deposit on the **anterior lens capsule** in pigment dispersion syndrome, appearing as fine dusting. - However, this deposition is **not referred to as Krukenberg's spindle**, which is specific to the posterior corneal surface. *Incorrect: Posterior surface of iris* - In pigment dispersion syndrome, **pigment is released FROM the posterior iris** due to mechanical rubbing against zonular fibers, creating **radial transillumination defects**. - However, Krukenberg's spindle refers to where pigment is **deposited** (corneal endothelium), not where it originates from.

Question 417: Which of the following features is characteristic of a fungal corneal ulcer?

A. The ulcer has feathery margins. (Correct Answer)
B. Symptoms are more prominent than signs.
C. The ulcer appears dry and grayish-white.
D. The ulcer is associated with diffuse corneal edema.

Explanation: ***The ulcer has feathery margins.*** - **Feathery margins** with satellite lesions are the **most characteristic feature** of fungal corneal ulcers, representing fungal hyphae spreading through the corneal stroma in a branching pattern - This infiltrative pattern with irregular, feathery borders is considered **pathognomonic** for fungal keratitis and is a key diagnostic feature - The feathery appearance helps distinguish fungal from bacterial ulcers clinically *The ulcer appears dry and grayish-white.* - While fungal ulcers can have a dry, grayish-white appearance, this is **less specific** and can be seen in other conditions - This feature is supportive but not as characteristic as the feathery margins - The texture relates to the minimal suppuration typical of fungal infections *The ulcer is associated with diffuse corneal edema.* - Diffuse corneal edema is more characteristic of **severe bacterial keratitis** or endothelial dysfunction - Fungal ulcers typically have more **localized infiltrates** with relatively less surrounding edema - When edema occurs, it's usually proportionate to the depth of infiltration *Symptoms are more prominent than signs.* - This describes **viral keratitis** (especially herpes simplex), where severe pain and photophobia occur with subtle signs - In **fungal ulcers**, the visible signs are usually **prominent** and correlate well with symptom severity - The lesion itself is typically quite evident on examination

Question 418: Acute corneal hydrops is seen in:

A. Keratoconus (Correct Answer)
B. Corneal dystrophy
C. Anterior staphyloma
D. Interstitial keratitis

Explanation: ***Keratoconus*** - **Acute corneal hydrops** is a classic complication of advanced **keratoconus**, occurring when a break in **Descemet's membrane** allows aqueous humor to enter the corneal stroma. - This leads to sudden onset of **corneal edema**, pain, and significant vision loss, often presenting with a milky white cornea due to stromal clouding. *Corneal dystrophy* - **Corneal dystrophies** are a group of genetic disorders that affect the clarity and structure of the cornea, typically causing progressive vision loss or recurrent epithelial erosions. - While some dystrophies can lead to corneal edema, **acute hydrops** specifically due to a Descemet's membrane rupture is not a characteristic feature. *Anterior staphyloma* - An **anterior staphyloma** is a bulging scar of the cornea and sclera, usually resulting from severe thinning or perforation, often associated with elevated intraocular pressure. - It is a structural deformation involving the entire globe's anterior segment, distinct from the sudden stromal edema of **corneal hydrops** caused by Descemet's rupture. *Interstitial keratitis* - **Interstitial keratitis** is characterized by non-ulcerative inflammation of the corneal stroma without primary involvement of the epithelium or endothelium, often associated with systemic infections like syphilis or Lyme disease. - It typically results in stromal opacification and vascularization ("salmon patch") but does not involve the acute rupture of Descemet's membrane seen in **hydrops**.

Question 419: Which is an emergency therapeutic indication of keratoplasty?

A. Keratoconus
B. Perforated corneal ulcer (Correct Answer)
C. Myopia
D. Hypermetropia

Explanation: ***Perforated corneal ulcer*** - A **perforated corneal ulcer** is an ocular emergency requiring urgent intervention to restore the integrity of the globe and prevent severe vision loss or endophthalmitis. Keratoplasty, in this context, acts as a tectonic graft to seal the perforation. - The emergent nature stems from the high risk of **intraocular infection** and **collapse of the anterior chamber**, which can lead to permanent damage and vision impairment. *Keratoconus* - While severe **keratoconus** can eventually lead to keratoplasty, it is typically an elective procedure performed to improve vision after other treatments like contact lenses are no longer effective. - It is a **slowly progressive condition** that does not usually pose an immediate threat to ocular integrity unless acute hydrops occurs, which itself may require different acute management. *Myopia* - **Myopia**, or nearsightedness, is a refractive error typically corrected with glasses, contact lenses, or elective refractive surgery (e.g., LASIK). - It is not a condition that warrants a **therapeutic or emergency keratoplasty**, as it does not involve structural compromise or disease of the cornea that would necessitate transplantation. *Hypermetropia* - **Hypermetropia**, or farsightedness, is also a refractive error, managed with corrective lenses or elective refractive surgery. - Similar to myopia, it does not involve a corneal disease process that would necessitate a **keratoplasty**, especially not on an emergency basis.

Question 420: The primary indication for collagen cross-linking is:

A. Pellucid marginal degeneration
B. Corneal ectasia after refractive surgery
C. Progressive corneal ectasia
D. Keratoconus (Correct Answer)

Explanation: ***Keratoconus*** - *Keratoconus* is a progressive disorder causing corneal thinning and a conical shape, leading to vision distortion. - *Collagen cross-linking (CXL)* is primarily indicated to halt the progression of keratoconus by strengthening corneal collagen fibers through riboflavin and UV-A light exposure. - This is the **most common and primary indication** for CXL, as it is FDA-approved and evidence-based for progressive keratoconus. *Pellucid marginal degeneration* - Pellucid marginal degeneration (PMD) involves a band of corneal thinning, usually in the inferior periphery, causing high astigmatism. - While CXL can be considered, PMD is less common and often managed with contact lenses or surgical techniques like crescentic resection. *Corneal ectasia after refractive surgery* - Corneal ectasia after refractive surgery is a complication where the cornea thins and bulges following procedures like LASIK. - CXL can be used to stabilize this condition, but it is a secondary indication, as keratoconus is the most common primary ectatic disease. *Progressive corneal ectasia* - Progressive corneal ectasia is a broad term describing any corneal thinning and bulging that worsens over time. - While keratoconus is a form of progressive corneal ectasia, the question asks for the primary indication, which points to the most common specific condition.

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

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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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