Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 361: Following are the causes of sudden loss of vision except?

A. Endophthalmitis
B. Angle closure glaucoma
C. Corneal ulceration (Correct Answer)
D. Central serous retinopathy

Explanation: ***Corneal ulceration*** - While a corneal ulcer can cause significant pain, redness, and some vision loss, it typically leads to a **gradual decrease in vision** over days, rather than a sudden, profound loss. - The vision loss associated with corneal ulceration is usually due to **stromal edema** and scarring, which develop progressively. *Endophthalmitis* - This is a severe inflammation of the intraocular fluids (vitreous and aqueous humor), often due to infection, which can lead to a **rapid and severe loss of vision**. - It often presents with **pain, red eye, and hypopyon**, alongside sudden vision changes. *Angle closure glaucoma* - An acute attack of angle closure glaucoma results in a **sudden increase in intraocular pressure**, causing rapid onset of **pain, headache, blurred vision, and halos around lights**. - This high pressure quickly damages the optic nerve, leading to **sudden vision loss** if not treated promptly. *Central serous retinopathy* - This condition involves fluid accumulation under the retina, causing a **sudden onset of blurred or distorted vision** (metamorphopsia) in the central visual field. - Patients often experience a **scotoma** (blind spot) and perceive objects as smaller (micropsia) or further away.

Question 362: A patient presents with eye pain, redness, and blurred vision after sleeping in contact lenses. Fluorescein staining reveals a corneal ulcer. What is the most appropriate management?

A. Topical antibiotics (Correct Answer)
B. Oral antibiotics
C. Topical corticosteroids
D. Saline irrigation

Explanation: ***Topical antibiotics*** - A **corneal ulcer**, especially in a contact lens wearer, is highly suspicious for **bacterial infection**, necessitating immediate and aggressive topical antibiotic therapy. - **Broad-spectrum antibiotics** (e.g., fluoroquinolones) are often started empirically and adjusted based on culture results. *Oral antibiotics* - **Systemic antibiotics** are generally not indicated for uncomplicated bacterial corneal ulcers, as they don't achieve sufficient concentrations in the cornea to be effective. - They may be considered for severe cases with limbal involvement or scleral extension, or if there is a concern for concurrent systemic infection. *Topical corticosteroids* - **Corticosteroids** are contraindicated in the initial management of suspected infectious corneal ulcers because they can suppress the immune response and worsen the infection. - They may be cautiously used later in treatment to reduce inflammation after the infection is well-controlled. *Saline irrigation* - While helpful for removing foreign bodies or debris, **saline irrigation alone** is insufficient to treat a bacterial corneal ulcer. - It does not eradicate the infection and delaying definitive antibiotic treatment can lead to severe complications.

Question 363: Why is fluorescein staining used in the diagnosis of corneal ulcers?

A. It assesses intraocular pressure.
B. Reveals epithelial damage under blue light (Correct Answer)
C. It detects viral particles in the cornea.
D. Highlights bacterial colonies on the corneal surface.

Explanation: ***Reveals epithelial damage under blue light*** - **Fluorescein** is a dye that stains areas of **epithelial disruption** on the cornea. - When viewed under a **cobalt blue light**, the stained areas fluoresce bright green, clearly indicating the presence and extent of a **corneal ulcer** or abrasion. *It assesses intraocular pressure.* - **Intraocular pressure** is measured using tonometry, not fluorescein staining. - Fluorescein can be minimally used with applanation tonometry but its primary role is not pressure assessment. *It detects viral particles in the cornea.* - Viral particles are too small to be directly detected by fluorescein staining. - Diagnosis of viral keratitis typically involves clinical appearance, sometimes confirmed by PCR or viral culture. *Highlights bacterial colonies on the corneal surface.* - While fluorescein outlines the area of infection, it does **not directly stain bacterial colonies**. - Bacterial colonies themselves are often visible with a slit lamp but fluorescein primarily stains the underlying epithelial defect.

Question 364: Which test is commonly used to diagnose keratoconus in patients with progressive myopia and irregular astigmatism?

A. Fluorescein staining
B. Tonometry
C. Corneal topography (Correct Answer)
D. Optical coherence tomography

Explanation: ***Corneal topography*** - **Corneal topography** is the gold standard for diagnosing and monitoring keratoconus as it provides detailed maps of the anterior and posterior corneal surfaces, allowing for the detection of subtle and overt corneal thinning and steepening. - It visualizes the characteristic **cone-shaped protrusion** and irregular astigmatism, which are hallmarks of the disease. *Fluorescein staining* - **Fluorescein staining** is primarily used to detect epithelial defects, ulcers, or abrasions on the cornea, not for assessing its shape or curvature. - While a severe case of keratoconus might show a **Fleischer's ring** (iron deposition) visible with cobalt blue light and fluorescein, it's not the primary diagnostic tool for the corneal shape itself. *Tonometry* - **Tonometry** measures intraocular pressure (IOP) and is used to screen for or monitor glaucoma. - It does not provide information about the **corneal shape, thickness**, or the presence of keratoconus. *Optical coherence tomography* - **Optical coherence tomography (OCT)** is an imaging technique used for high-resolution cross-sectional imaging of the retina and optic nerve, and increasingly for anterior segment structures including corneal thickness. - While anterior segment OCT can provide valuable information about **corneal thickness and posterior corneal surface**, it is not as comprehensively diagnostic for the overall corneal curvature and irregularity of keratoconus as corneal topography.

Question 365: Which part of the eye is primarily affected in keratitis?

A. Cornea (Correct Answer)
B. Lens
C. Retina
D. Vitreous

Explanation: ***Cornea*** - **Keratitis** is an inflammation of the **cornea**, the transparent outer layer of the eye. - This condition can cause pain, redness, blurred vision, and sensitivity to light. *Lens* - The **lens** is primarily affected in conditions like **cataracts**, where it becomes cloudy. - Inflammation of the lens itself is rare and not referred to as keratitis. *Retina* - The **retina** is involved in conditions such as **retinitis** or **macular degeneration**, which affect light perception. - **Keratitis** does not directly involve the retina. *Vitreous* - The **vitreous humor** is the gel-like substance filling the eye, and its inflammation is called **vitritis**. - This is distinct from keratitis, which is specific to the cornea.

Question 366: Which layer of the cornea is affected in keratoconus?

A. Stroma (Correct Answer)
B. Epithelium
C. Endothelium
D. Bowman's layer

Explanation: ***Stroma*** - **Keratoconus** is primarily a **stromal disease** characterized by progressive thinning and weakening of the corneal stroma, the thickest layer comprising 90% of corneal thickness. - The fundamental pathology involves **stromal collagen disorganization**, reduced keratocyte density, and biomechanical instability leading to the characteristic conical protrusion. - Stromal thinning with loss of collagen lamellae is the **primary and earliest significant change** that drives the ectatic process. - Clinical signs like Vogt's striae (stress lines in stroma) and Fleischer ring (iron deposition at cone base) reflect stromal pathology. *Bowman's layer* - Bowman's layer shows **breaks and ruptures** in keratoconus, but these are **secondary changes** resulting from the progressive stromal ectasia and biomechanical stress. - These breaks occur in **moderate to advanced disease**, not as the initiating pathological event. - Acute hydrops (rupture of Descemet's membrane with stromal edema) can occur when ectasia is severe. *Epithelium* - The **epithelium** remains largely intact but shows **compensatory thinning** over the apex of the cone and thickening in the periphery. - Epithelial iron deposition (Fleischer ring) and recurrent erosions may occur but are not the primary pathology. *Endothelium* - The **endothelium** is typically **well-preserved** in keratoconus until very advanced stages. - Endothelial dysfunction is characteristic of other corneal diseases like Fuchs' endothelial dystrophy, not keratoconus.

Question 367: Which of the following is used in the diagnosis of corneal dystrophies?

A. Specular microscopy (Correct Answer)
B. Fluorescein angiography
C. Optical coherence tomography
D. Fundus photography

Explanation: ***Specular microscopy*** - This technique is the **gold standard for diagnosing corneal endothelial dystrophies** as it allows for **direct visualization and quantitative analysis of endothelial cells** and their morphology. - Many corneal dystrophies, particularly **Fuchs endothelial dystrophy**, are characterized by specific changes in endothelial cell density, pleomorphism, and polymegathism that are best evaluated with specular microscopy. - Provides **cellular-level detail** that is critical for early detection and monitoring of endothelial dystrophies. *Fluorescein angiography* - This diagnostic tool is primarily used for evaluating **retinal and choroidal vasculature**, especially in conditions like **diabetic retinopathy** or **age-related macular degeneration**. - It involves injecting fluorescein dye and observing its flow through posterior segment vessels, which is **not relevant for corneal diagnosis**. *Optical coherence tomography* - While **anterior segment OCT (AS-OCT) is indeed used for imaging corneal dystrophies** and provides excellent cross-sectional visualization of corneal layers, stromal opacities, and epithelial changes, it does **not provide the cellular-level endothelial detail** offered by specular microscopy. - AS-OCT is useful for stromal dystrophies (granular, lattice, macular) and measuring corneal thickness, but **specular microscopy remains superior for endothelial assessment**, which is crucial for the most commonly tested corneal dystrophies. *Fundus photography* - This technique captures **images of the posterior pole of the eye**, including the retina, optic disc, and macula. - It is utilized for documenting and monitoring conditions affecting the **retina and optic nerve**, not the anterior corneal structures.

Question 368: A 22-year-old male presents with intense pain, photophobia, and a ring-like corneal infiltrate in his left eye. He frequently swims in lakes. What is the most likely diagnosis?

A. Acanthamoeba keratitis (Correct Answer)
B. Herpes simplex keratitis
C. Bacterial keratitis
D. Fungal keratitis

Explanation: ***Acanthamoeba keratitis*** - Intense pain, photophobia, and a **ring-like corneal infiltrate** are classic signs of Acanthamoeba keratitis. - Exposure to **contaminated water**, such as swimming in lakes, is a common risk factor, especially for contact lens wearers. *Herpes simplex keratitis* - Typically presents with a **dendritic ulcer pattern** on the cornea, which is not described here. - While it can cause pain and photophobia, the characteristic ring infiltrate points away from HSV. *Bacterial keratitis* - Often presents with a **purulent discharge** and a **rapidly progressing stromal infiltrate**, which may or may not be ring-shaped. - While it can cause intense pain, the specific exposure to lake water and the clear description of a ring infiltrate make Acanthamoeba more likely. *Fungal keratitis* - Usually follows **ocular trauma with vegetative matter** or in immunocompromised individuals, often presenting with a feathery-edged infiltrate. - While contact lens wear is a risk factor, the description of a **ring infiltrate** and association with fresh water directly points to Acanthamoeba.

Question 369: A 35-year-old male presents with severe eye pain, photophobia, and blurred vision. Examination reveals a dendritic ulcer on the cornea. What is the initial treatment?

A. Topical antiviral medication (Correct Answer)
B. Topical antibiotic drops
C. Oral corticosteroids
D. Cycloplegic drops

Explanation: ***Topical antiviral medication*** - A **dendritic ulcer** is the classic pathognomonic sign of **herpes simplex keratitis**, which requires prompt antiviral treatment. - Topical antivirals like **ganciclovir gel** or **trifluridine ophthalmic solution** are first-line to inhibit viral replication and promote healing. *Topical antibiotic drops* - While topical antibiotics are used for **bacterial keratitis**, they are ineffective against viral infections like herpes simplex. - Inappropriate use of antibiotics can lead to **antibiotic resistance** and may delay effective treatment. *Oral corticosteroids* - **Corticosteroids** are generally contraindicated in active epithelial herpes simplex keratitis because they can worsen the infection and promote viral replication. - They might be used cautiously in later stages for **immune-mediated stromal keratitis** under specialist supervision. *Cycloplegic drops* - **Cycloplegics**, such as atropine or cyclopentolate, relieve ciliary spasm and pain associated with corneal inflammation. - While they serve as useful **adjunctive therapy** for symptom relief, they do not treat the underlying **viral infection** and are not the **initial/primary treatment** for herpes simplex keratitis.

Question 370: A 28-year-old female with a history of contact lens wear presents with a painful red eye and decreased vision. A slit-lamp examination reveals a central corneal ulcer with hypopyon. What is the most likely causative organism?

A. Staphylococcus aureus
B. Pseudomonas aeruginosa (Correct Answer)
C. Herpes simplex virus
D. Candida albicans

Explanation: ***Pseudomonas aeruginosa*** - This organism is a common cause of **severe bacterial keratitis** in contact lens wearers due to its ability to adhere to lenses and produce potent toxins. - Its rapid progression can lead to a **central corneal ulcer** with significant inflammation and often a **hypopyon**. *Staphylococcus aureus* - While *S. aureus* can cause bacterial keratitis and corneal ulcers, it is less commonly associated with the rapid, aggressive course often seen with contact lens-related infections, which characteristically involve a prominent **hypopyon**. - Its infections tend to be more indolent or localized in comparison to *Pseudomonas*. *Herpes simplex virus* - HSV keratitis presents with characteristic **dendritic ulcers** or geographic ulcers, which differ in morphology from typical bacterial ulcers. - While it can cause pain, redness, and decreased vision, it is not primarily associated with contact lens wear and usually does not cause a pronounced **hypopyon** without secondary bacterial infection. *Candida albicans* - Fungal keratitis, including that caused by *Candida*, usually occurs after **trauma** involving plant matter or in immunocompromised individuals, not typically in routine contact lens wear. - Fungal ulcers tend to have a **feathery border** and **satellite lesions**, distinct from the described central corneal ulcer.

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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