Diseases of the Cornea Practice Questions

Q: Topical steroids can be used in which of the following keratitis conditions:

Disciform keratitis. ***Disciform keratitis*** - This condition is typically an **immune-mediated stromal inflammation** of the cornea, often following a **herpes simplex virus (HSV) infection**. - **Topical corticosteroids** (with concurrent antiviral therapy) are crucial for reducing the inflammation and edema associated with disciform keratitis, preserving corneal clarity. - This represents **HSV stromal keratitis** where the pathology is immunological rather than active viral replication. *Herpetic dendritic keratitis* - This is **active viral replication** of herpes simplex virus in the corneal epithelium, characterized by a **dendritic ulcer**. - **Topical steroids are strictly contraindicated** as they can worsen viral replication, leading to geographic ulcers and potentially corneal perforation. - Treatment requires antivirals only (acyclovir, ganciclovir). *Bacterial keratitis* - This is **acute bacterial infection** of the cornea, typically presenting as a corneal ulcer with purulent infiltrate. - **Topical steroids are contraindicated during active infection** as they suppress the immune response and can worsen bacterial proliferation. - Treatment focuses on intensive topical antibiotics; steroids may only be considered after infection control with close monitoring. *Fungal keratitis* - This is **fungal infection** of the cornea, often following trauma with vegetative matter, presenting with feathery infiltrates and satellite lesions. - **Topical steroids are absolutely contraindicated** as they dramatically worsen fungal infections and can lead to corneal perforation. - Treatment requires prolonged antifungal therapy (natamycin, voriconazole).

Q: Corneal tattooing is done by ?

India ink. ***India ink*** - **India ink (sterile carbon particles)** is the **most traditional and widely used** material for corneal tattooing - It provides **excellent dark pigmentation** to camouflage **leucomatous corneal scars** and improve cosmetic appearance - Modern technique uses **sterile preparations** to prevent complications - Also known as **carbon tattooing**, it effectively masks unsightly white corneal opacities *Titanium oxide* - **Titanium oxide** is a white pigment with good biocompatibility - While it can be used for white pigmentation, it is **not the standard or most commonly used** agent for corneal tattooing - Limited application compared to India ink *Silver nitrate* - **Silver nitrate** is used for **chemical cauterization** and as an antiseptic - It is **not used for corneal tattooing** as it causes tissue damage and discoloration - Historical use was for treating corneal ulcers, not for cosmetic tattooing *Gold nanoparticles* - **Gold salts (chloroauric acid)** have been used historically for corneal tattooing - Provides a **golden-brown pigmentation** - Less commonly used today compared to India ink due to **cost and availability**

Q: Topical antiviral drugs are not indicated in:

Metaherpetic ulcer. ***Metaherpetic ulcer*** - Metaherpetic ulcers are **neurotrophic ulcers** that develop as a result of chronic epithelial damage and impaired healing after a herpes simplex virus (HSV) infection, but they are not an active viral replication process. - Topical antivirals are ineffective because there is **no replicating virus** to target; management focuses on promoting corneal healing and preventing secondary infections. *Dendritic ulcer* - A dendritic ulcer is a classic sign of **active HSV keratitis** with replicating virus in the epithelial cells. - Topical antiviral drugs (e.g., acyclovir, ganciclovir) are the **first-line treatment** to inhibit viral replication and promote epithelial healing. *Stromal necrotizing keratitis* - This condition involves **inflammation and necrosis** in the corneal stroma, often due to an immune reaction to HSV antigens rather than direct viral invasion. - While topical antivirals may be used to suppress any residual replicating virus, **topical corticosteroids are often necessary** to control the inflammation, and close monitoring is crucial due to the risk of steroid-induced complications. *All of the options* - This option is incorrect because topical antiviral drugs *are* indicated for **dendritic ulcers** and sometimes as adjunctive therapy for **stromal necrotizing keratitis** where active viral replication might be contributing.

Q: For transplantation, cornea is preserved in:

Modified MK medium. ***Modified MK medium*** - The **Modified MK medium (McCarey-Kaufman medium)** is a widely accepted and effective **cold storage medium** for corneal preservation. - It contains nutrients (glutathione, adenosine), osmotic agents (dextran), and antibiotics to maintain corneal viability and transparency for up to **4-7 days** at 4°C. *Wet medium* - The term "wet medium" is **non-specific** and does not refer to a standard corneal preservation solution. - While cornea is stored in a liquid medium, this option lacks the specificity of established preservation techniques. *Glycerine medium* - **Glycerine** can be used for **tissue preservation** but is not the standard medium for routine corneal storage for transplantation. - Modern corneal preservation relies on specialized cold storage media that maintain endothelial cell viability, not glycerine-based preservation. *All of the options* - This option is incorrect because "Wet medium" is not a standard preservation term, and "Glycerine medium" is not the primary method for routine corneal storage for transplantation. - Only specific, scientifically validated preservation solutions like Modified MK medium are routinely used to ensure donor corneal viability.

Q: Avascular structure of the eye is -

Cornea. ***Cornea*** - The **cornea** is transparent and relies on **aqueous humor** for nutrients and oxygen directly from the air and tears, making it avascular. - Its avascularity is crucial for maintaining **transparency**, which is essential for light transmission to the retina. *Retina* - The retina is a highly **metabolically active** tissue that requires a rich blood supply. - It receives blood primarily from the **choroid** and the central retinal artery. *Ciliary body* - The ciliary body is part of the **uvea** and is highly vascular, responsible for producing **aqueous humor**. - It contains the **ciliary muscle**, which controls the shape of the lens for accommodation. *Conjunctiva* - The conjunctiva is a **vascular mucous membrane** lining the inner surface of the eyelids and covering the anterior sclera. - Its blood vessels are visible and can become **engorged** during inflammation or irritation (e.g., conjunctivitis).

Q: Salmon patch is seen in -

Interstitial keratitis. **Interstitial keratitis** - **Salmon patch** is a classical vascularization pattern seen in **interstitial keratitis**, particularly in cases of treated or resolving syphilitic interstitial keratitis. - This reddish-orange discoloration results from the infiltration of the corneal stroma by **blood vessels**. *Disciform keratitis* - Characterized by a **disc-shaped stromal edema** with overlying epithelial defects or keratic precipitates. - It is typically caused by herpes simplex virus and does not present with a "salmon patch" but rather a **stromal haze**. *Phlyctenular keratitis* - Presents as **nodular lesions** (phlyctenules) on the conjunctiva or cornea, often associated with a **Type IV hypersensitivity reaction** to microbial antigens like *Staphylococcus* or *Mycobacterium tuberculosis*. - While it can cause corneal scarring and vascularization, it does not typically produce the diffuse, reddish "salmon patch" appearance. *Acne rosacea* - Can cause **ocular rosacea**, leading to symptoms such as chronic conjunctivitis, blepharitis, and in severe cases, keratitis. - Though it can cause corneal inflammation and vascularization, the characteristic "salmon patch" is not a hallmark feature of **rosacea keratitis**.

Q: Preferred suture for corneal graft is:

10-0 nylon. ***10-0 nylon*** - **10-0 nylon** is the preferred suture material for corneal grafts due to its **monofilament structure**, which reduces the risk of infection and inflammation. - Its **fine gauge** (10-0) minimizes tissue trauma and allows for precise wound approximation, crucial for maintaining corneal clarity and astigmatism control. *9-0 prolene* - While Prolene (polypropylene) is also a monofilament suture, **9-0 Prolene** is typically thicker than 10-0 nylon and may induce more astigmatism. - It is less commonly used for corneal grafts as nylon offers superior handling and knot security for this delicate tissue. *8-0 silk* - **8-0 silk** is a braided, multifilament suture, which can harbor bacteria and lead to increased inflammation and infection risk in the avascular cornea. - It is also thicker than 10-0 nylon, making it less suitable for the precise, fine suturing required in corneal transplantation. *7-0 vicryl* - **7-0 Vicryl** (polyglactin 910) is an absorbable suture, which is generally not suitable for corneal grafts where long-term wound support is required. - The absorption process can cause inflammation and unpredictable changes in suture tension, leading to astigmatism and graft instability.

Q: 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?

Topical antibiotics. ***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.

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

Reveals epithelial damage under blue light. ***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.

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

Corneal topography. ***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 1

Topical steroids can be used in which of the following keratitis conditions:

Accepted Answer

Disciform keratitis

Answer

Herpetic dendritic keratitis

Answer

Bacterial keratitis

Answer

Fungal keratitis

Question 2

Corneal tattooing is done by ?

Accepted Answer

India ink

Answer

Silver nitrate

Answer

Gold nanoparticles

Answer

Titanium oxide

Question 3

Topical antiviral drugs are not indicated in:

Accepted Answer

Metaherpetic ulcer

Answer

Dendritic ulcer

Answer

Stromal necrotizing keratitis

Answer

All of the options

Question 4

For transplantation, cornea is preserved in:

Accepted Answer

Modified MK medium

Answer

Wet medium

Answer

Glycerine medium

Answer

All of the options

Question 5

Avascular structure of the eye is -

Accepted Answer

Cornea

Answer

Retina

Answer

Ciliary body

Answer

Conjunctiva

Question 6

Salmon patch is seen in -

Accepted Answer

Interstitial keratitis

Answer

Disciform keratitis

Answer

Phlyctenular keratitis

Answer

Acne rosacea

Question 7

Preferred suture for corneal graft is:

Accepted Answer

10-0 nylon

Answer

9-0 prolene

Answer

8-0 silk

Answer

7-0 vicryl

Question 8

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?

Accepted Answer

Topical antibiotics

Answer

Oral antibiotics

Answer

Topical corticosteroids

Answer

Saline irrigation

Question 9

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

Accepted Answer

Reveals epithelial damage under blue light

Answer

It assesses intraocular pressure.

Answer

It detects viral particles in the cornea.

Answer

Highlights bacterial colonies on the corneal surface.

Question 10

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

Accepted Answer

Corneal topography

Answer

Fluorescein staining

Answer

Tonometry

Answer

Optical coherence tomography

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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