Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 371: A 40-year-old woman presents with recurrent corneal erosions and has a history of trauma to the eye. Which layer of the cornea is most likely involved?

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

Explanation: ***Epithelium*** - **Recurrent corneal erosions** often result from a defect in the adhesion of the **corneal epithelium** to the underlying Bowman's layer and basement membrane. - A history of **trauma** can disrupt these adhesion complexes, making the epithelium prone to repeated detachments. *Stroma* - The **corneal stroma** is the thickest layer and provides structural integrity; conditions affecting it typically lead to scarring, opacification, or thinning, rather than recurrent erosions. - While stromal injury can occur with trauma, recurrent erosions specifically point to issues with the superficial adhesive layers, not the bulk of the stroma itself. *Endothelium* - The **corneal endothelium** is the innermost layer responsible for maintaining corneal deturgescence (fluid balance) through its pump function. - Endothelial dysfunction typically causes **corneal edema** and cloudiness, not recurrent erosions. *Descemet's membrane* - **Descemet's membrane** is the basement membrane of the endothelium and is highly resistant to trauma. - Damage to Descemet's membrane is usually associated with significant *blunt trauma* or specific genetic disorders, and its rupture can lead to acute hydrops or swelling, not recurrent erosions.

Question 372: Placido disc is used for diagnosing which of the following conditions?

A. Keratoconus (Correct Answer)
B. Uveitis
C. Retinoblastoma
D. Retinal detachment

Explanation: ***Keratoconus*** - A **Placido disc**, or **keratoscope**, uses concentric rings projected onto the cornea to assess its shape and detect irregularities. - In **keratoconus**, the cornea thins and protrudes into a cone-like shape, distorting the reflected rings of the Placido disc. *Uveitis* - **Uveitis** is an inflammation of the uvea, the middle layer of the eye, which is diagnosed through examination of intraocular structures and symptoms like pain, redness, and light sensitivity. - The **Placido disc** is not used for diagnosing intraocular inflammation but rather for assessing corneal surface abnormalities. *Retinoblastoma* - **Retinoblastoma** is a malignant tumor of the retina, typically diagnosed with ophthalmoscopy (to visualize the retina), imaging studies (like ultrasound or MRI), and genetic testing. - The **Placido disc** examines the corneal surface and has no role in detecting retinal tumors. *Retinal detachment* - **Retinal detachment** involves the separation of the retina from its underlying support structures, diagnosed through ophthalmoscopy to visualize the detached retina. - The **Placido disc** evaluates the cornea, not the retina, and therefore cannot diagnose retinal detachment.

Question 373: In which condition is there a deficiency in the mucin layer of the tear film?

A. Keratoconjunctivitis sicca (dry eye syndrome) (Correct Answer)
B. Aqueous tear deficiency due to lacrimal gland dysfunction
C. Obstruction in tear drainage pathways
D. Corneal damage due to viral infection

Explanation: ***Keratoconjunctivitis sicca (dry eye syndrome)*** - Dry eye syndrome has **multiple subtypes**, including **mucin-deficient dry eye** caused by goblet cell dysfunction or loss. - Conditions causing goblet cell damage (Stevens-Johnson syndrome, ocular pemphigoid, vitamin A deficiency, chronic conjunctivitis) lead to **mucin layer deficiency** as a component of dry eye. - The **mucin layer**, produced by conjunctival goblet cells, is essential for tear film adhesion to the corneal epithelium; its deficiency prevents proper wetting even with adequate aqueous. - While aqueous-deficient dry eye is more common, **mucin-deficient dry eye** is a recognized subtype specifically addressing the question. *Aqueous tear deficiency due to lacrimal gland dysfunction* - This specifically describes **aqueous layer deficiency**, not mucin deficiency. - The lacrimal gland produces the aqueous component; this option addresses a different layer of the tear film. - Mucin production by goblet cells would be unaffected in isolated lacrimal gland dysfunction. *Obstruction in tear drainage pathways* - This causes **epiphora** (excessive tearing/overflow), not deficiency of any tear film component. - The problem is impaired drainage through the nasolacrimal system, leading to tear accumulation rather than reduced tear film quality. *Corneal damage due to viral infection* - Viral keratitis causes **epithelial damage and inflammation**, not primary mucin layer deficiency. - While secondary effects on tear film may occur, the underlying pathology is infectious/inflammatory, not goblet cell dysfunction.

Question 374: Which of the following is not a feature of fungal corneal ulcer?

A. Symptoms are more pronounced than signs (Correct Answer)
B. Ulcer with sloughing margins
C. Fixed hypopyon
D. Fungal hyphae are seen on KOH mount

Explanation: ***Symptoms are more pronounced than signs*** - This statement is characteristic of ***viral keratitis***, where the patient's discomfort and symptoms can be disproportionately severe compared to the objective clinical findings. - In ***fungal corneal ulcers***, the signs (like the ulcer's appearance, feathery margins) are typically more prominent and extensive relative to the patient's milder symptomatic complaints. *Fixed hypopyon* - A ***fixed hypopyon***, which is a collection of pus in the anterior chamber that does not shift with head movements, is a classic feature of ***fungal corneal ulcers***. - This is due to the robust inflammatory response and the tendency of fungi to produce a more viscous exudate that settles and adheres. *Ulcer with sloughing margins* - ***Sloughing margins*** are indicative of tissue necrosis and liquefaction, which can be seen in aggressive fungal infections of the cornea. - This appearance suggests extensive tissue destruction and can contribute to the deeper penetration of the infection. *Fungal hyphae are seen on KOH mount* - The presence of ***fungal hyphae*** on a ***potassium hydroxide (KOH) mount*** of corneal scrapings is a definitive diagnostic feature of a fungal corneal ulcer. - KOH dissolves cellular debris, making the fungal elements (hyphae or spores) more visible under a microscope.

Question 375: Which of the following is not a phase involved in corneal epithelial repair?

A. Cell migration
B. Cell adhesion
C. Cell fusion (Correct Answer)
D. Cell proliferation

Explanation: ***Cell fusion*** - Cell fusion, the **merging of cell membranes** from two or more cells to form a single cell, is not recognized as a mechanism involved in typical corneal epithelial repair. - Corneal epithelial healing primarily relies on the coordinated actions of **migration**, **proliferation**, and **differentiation** of existing cells. *Cell migration* - **Epithelial cells** at the wound edge flatten and migrate to cover the denuded area, forming a monolayer. - This initial phase is crucial for rapidly **closing the defect** and preventing infection. *Cell adhesion* - New cells need to **adhere to the underlying basement membrane** and to each other to maintain structural integrity. - **Integrins** and other adhesion molecules play a critical role in re-establishing proper connections. *Cell proliferation* - Once the defect is covered by migrating cells, **basal cells** begin to proliferate to restore the original cell layers and thickness of the epithelium. - This phase rebuilds the **stratified squamous epithelium**.

Question 376: Iron deposition line at edge of pterygium on corneal epithelium is known as?

A. Stocker's line (Correct Answer)
B. KF Ring
C. Fleischer ring
D. Ferry's line

Explanation: ***Stocker's line*** - **Stocker's line** is a **corneal iron deposition line** that occurs at the leading edge of a **pterygium**. - It is formed due to the accumulation of **iron pigment** within the **corneal epithelium** as a result of tear film stagnation induced by the elevated pterygium. *KF Ring* - **Kayser-Fleischer (KF) ring** is a **copper deposition** in Descemet's membrane of the **cornea**, indicative of **Wilson's disease**. - It presents as a **golden-brown or green-brown ring** and is not associated with pterygium. *Fleischer ring* - **Fleischer ring** is a **circumferential iron deposition** in the **corneal epithelium** at the base of the **cone in keratoconus**. - This ring occurs due to tear film pooling at the base of the ectatic cornea, leading to iron accumulation, and is distinct from pterygium-associated iron lines. *Ferry's line* - **Ferry's line** is an **iron deposition line** seen in the **corneal epithelium** around the **filtering bleb after glaucoma surgery**. - It is also caused by tear film alterations and iron accumulation, but its location and etiology differ from Stocker's line.

Question 377: Which of the following is the causative organism of Acanthamoeba keratitis?

A. Plasmodium
B. Acanthamoeba (Correct Answer)
C. Toxoplasma
D. W. bancrofti

Explanation: ***Acanthamoeba*** - **Acanthamoeba keratitis** is a serious and painful infection of the eye's cornea caused by species of the **free-living amoeba Acanthamoeba**. - This infection is commonly associated with contact lens wear, particularly when proper hygiene and disinfection practices are not followed. *Plasmodium* - **Plasmodium** species are the causative agents of **malaria**, a mosquito-borne infectious disease affecting red blood cells and the liver. - It does not cause eye infections like keratitis and is transmitted through the bite of an infected Anopheles mosquito. *Toxoplasma* - **Toxoplasma gondii** is an intracellular parasitic protozoon that causes **toxoplasmosis**, which can manifest as chorioretinitis, encephalitis, or lymphadenopathy. - While it can affect the eye (**ocular toxoplasmosis**), it causes retinitis or chorioretinitis, not keratitis. *W. bancrofti* - **Wuchereria bancrofti** is a filarial nematode that causes **lymphatic filariasis**, an infection leading to elephantiasis and other lymphatic disorders. - It primarily affects the lymphatic system and subcutaneous tissues, not the cornea.

Question 378: Munson's sign is a feature of ?

A. Keratoconus (Correct Answer)
B. Corneal ulcer
C. Pterygium
D. Posterior staphyloma

Explanation: ***Keratoconus*** - **Munson's sign** is observed in advanced keratoconus, where the **conical protrusion of the cornea** indents the lower eyelid on downgaze. - This sign indicates significant **corneal thinning and steepening**. *Corneal ulcer* - A **corneal ulcer** is an open sore on the cornea, often caused by infection or trauma. - It presents with pain, redness, tearing, and photophobia, and does not cause **Munson's sign**. *Pterygium* - **Pterygium** is a triangular growth of conjunctival tissue that extends onto the cornea. - It is typically associated with UV exposure and does not cause corneal shape changes leading to **Munson's sign**. *Posterior staphyloma* - A **posterior staphyloma** is an outpouching of the posterior sclera, often seen in high myopia. - This condition affects the posterior segment of the eye and does not manifest with **Munson's sign**, which is an anterior corneal finding.

Question 379: All are true about Bullous keratopathy except which of the following?

A. Seen in Macular dystrophy (Correct Answer)
B. Lenses can be prescribed for such patients
C. Seen in Fuchs' dystrophy
D. Treatment is lamellar keratoplasty

Explanation: ***Seen in Macular dystrophy*** - **Bullous keratopathy** is a condition caused by endothelial dysfunction leading to corneal edema and bullae formation. - While macular corneal dystrophy is a condition characterized by corneal clouding due to mucopolysaccharide deposits in the stroma, it typically does not directly cause bullous keratopathy. *Treatment is lamellar keratoplasty* - **Lamellar keratoplasty** (e.g., DSAEK, DMEK) is a common surgical treatment for bullous keratopathy, where diseased posterior corneal layers are replaced. - The goal is to replace the dysfunctional endothelium and restore corneal clarity and function. *Lenses can be prescribed for such patients* - **Contact lenses**, particularly bandage contact lenses, can be prescribed to patients with bullous keratopathy to protect the cornea and alleviate pain. - They act as a physical barrier against ruptured bullae, promoting epithelial healing and comfort. *Seen in Fuchs' dystrophy* - **Fuchs' endothelial dystrophy** is a common cause of bullous keratopathy, where there's a progressive loss of corneal endothelial cells. - This endothelial dysfunction leads to an accumulation of fluid within the cornea, causing edema and the formation of epithelial bullae.

Question 380: Quantification of corneal sensation is done by?

A. Pachymeter
B. Keratometer
C. Aesthesiometer (Correct Answer)
D. Tonometer

Explanation: ***Aesthesiometer*** - An **aesthesiometer** is a specialized device used to measure the **corneal sensation** or sensitivity, typically by applying a controlled stimulus to the corneal surface. - It helps in diagnosing conditions affecting **corneal nerves**, such as **diabetic neuropathy** or post-surgical nerve damage. *Pachymeter* - A **pachymeter** is an ultrasonic device used to measure the **central corneal thickness (CCT)**. - This measurement is crucial for **intraocular pressure (IOP)** interpretation and evaluating conditions like **corneal edema** or **Fuchs' endothelial dystrophy**. *Keratometer* - A **keratometer** is an ophthalmic instrument used to measure the **curvature of the anterior surface of the cornea**. - It is primarily used to assess **corneal astigmatism** and to fit **contact lenses**. *Tonometer* - A **tonometer** is an instrument used to measure **intraocular pressure (IOP)**, which is essential for diagnosing and managing **glaucoma**. - It does not quantify corneal sensation but rather the **fluid pressure within the eye**.

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

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