Diseases of the Cornea Practice Questions

Q: A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:

Keratoconus. ***Keratoconus*** - **Keratoconus** is a progressive disorder where the cornea thins and protrudes into a cone shape, leading to irregular astigmatism and frequent changes in glasses prescription. - This condition commonly presents in young adults and is characterized by **rapid, repeated changes** in both spherical and cylindrical components due to progressive corneal distortion. - The irregular corneal shape makes it difficult to achieve stable, satisfactory vision correction with glasses alone. *Cataract* - A **cataract** is a clouding of the eye's natural lens, which causes blurred vision, glare, and difficulty seeing at night. - While it can cause a "myopic shift" leading to prescription changes, it is more common in older individuals (>50 years) and the changes are typically slower and less frequent than in keratoconus. *Glaucoma* - **Glaucoma** is a group of eye conditions that damage the optic nerve, often due to high intraocular pressure, leading to peripheral vision loss and eventually blindness. - It does not cause changes in refractive error or require frequent updates to glasses prescriptions. - Visual changes are related to field defects, not refractive changes. *Pathological myopia* - **Pathological myopia** is a severe form of nearsightedness where the eye elongates excessively, leading to progressive increases in myopic refractive error. - While it can cause prescription changes in young adults, the progression is typically more **gradual and predictable** (mainly increasing spherical myopia) compared to the **rapid, irregular changes** seen in keratoconus. - Keratoconus is distinguished by frequent changes in astigmatism due to irregular corneal shape, whereas pathological myopia mainly affects spherical power.

Q: For transplantation, cornea can be removed from dead body up to:

24 hours. ***24 hours*** - Corneas can be harvested from a deceased donor within **24 hours** of death, provided the body is kept in a cool environment. - This time frame allows for adequate perfusion of the corneal tissue and maintains **cellular viability** for successful transplantation. *6 hours* - While some organs have a very limited window for retrieval, **corneas** generally have a longer viability compared to highly metabolic organs. - A 6-hour window is often too short and would significantly limit the availability of corneal tissue for transplantation. *18 hours* - An 18-hour window is a reasonable period but is often extended to 24 hours under proper storage conditions. - Extending to **24 hours** maximizes the opportunity for procurement and does not significantly compromise tissue quality for corneal transplantation. *12 hours* - A 12-hour window, although longer than 6 hours, is still a conservative estimate for corneal retrieval. - With advancements in preservation techniques, the **viability period** for corneas is now widely accepted to be up to 24 hours post-mortem.

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.

Question 1

A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:

Accepted Answer

Keratoconus

Answer

Cataract

Answer

Glaucoma

Answer

Pathological myopia

Question 2

For transplantation, cornea can be removed from dead body up to:

Accepted Answer

24 hours

Answer

6 hours

Answer

18 hours

Answer

12 hours

Question 3

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 4

Corneal tattooing is done by ?

Accepted Answer

India ink

Answer

Silver nitrate

Answer

Gold nanoparticles

Answer

Titanium oxide

Question 5

Topical antiviral drugs are not indicated in:

Accepted Answer

Metaherpetic ulcer

Answer

Dendritic ulcer

Answer

Stromal necrotizing keratitis

Answer

All of the options

Question 6

For transplantation, cornea is preserved in:

Accepted Answer

Modified MK medium

Answer

Wet medium

Answer

Glycerine medium

Answer

All of the options

Question 7

Avascular structure of the eye is -

Accepted Answer

Cornea

Answer

Retina

Answer

Ciliary body

Answer

Conjunctiva

Question 8

Salmon patch is seen in -

Accepted Answer

Interstitial keratitis

Answer

Disciform keratitis

Answer

Phlyctenular keratitis

Answer

Acne rosacea

Question 9

Preferred suture for corneal graft is:

Accepted Answer

10-0 nylon

Answer

9-0 prolene

Answer

8-0 silk

Answer

7-0 vicryl

Question 10

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

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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