Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 351: Herbert's pits are seen in:

A. Chlamydial conjunctivitis (Correct Answer)
B. Gonococcal conjunctivitis
C. Vernal conjunctivitis
D. Atopic conjunctivitis

Explanation: ***Chlamydial conjunctivitis*** - **Herbert's pits** are pathognomonic for **trachoma**, a chronic form of chlamydial conjunctivitis caused by *Chlamydia trachomatis* serovars A-C. - They represent healed **follicles** on the superior tarsal conjunctiva, leading to characteristic stellate or linear scarring. *Gonococcal conjunctivitis* - This is an **acute, severe bacterial infection** that typically causes copious purulent discharge and significant edema. - It does not lead to the formation of Herbert's pits, which are sequelae of chronic follicular inflammation. *Vernal conjunctivitis* - A form of chronic allergic conjunctivitis, characterized by **"cobblestone papillae"** on the upper tarsal conjunctiva and **Horner-Trantas dots** at the limbus. - It is not associated with Herbert's pits; its pathophysiology involves mast cell degranulation and allergic inflammation. *Atopic conjunctivitis* - This is often seen in individuals with **atopic dermatitis, asthma, or allergic rhinitis**, presenting with itching, redness, tearing, and sometimes corneal complications. - It does not manifest with follicles or subsequent scarring like Herbert's pits, which are specific to trachoma.

Question 352: In uveitis, site of keratic precipitate is:

A. Lens anterior capsule
B. Corneal endothelium (Correct Answer)
C. Lens posterior capsule
D. Corneal stroma

Explanation: ***Corneal endothelium*** - **Keratic precipitates (KPs)** are inflammatory cellular deposits that adhere to the **posterior surface of the cornea**, specifically the endothelial layer, in uveitis. - They represent aggregates of inflammatory cells, such as macrophages and lymphocytes, that have migrated from the inflamed anterior chamber. *Lens anterior capsule* - The **anterior capsule of the lens** is a smooth, acellular membrane and does not typically accumulate inflammatory deposits like **keratic precipitates**. - While inflammatory cells can be observed in the **anterior chamber**, they do not specifically adhere to the lens capsule in this manner. *Lens posterior capsule* - Similar to the anterior capsule, the **posterior capsule of the lens** is not the site for deposition of **keratic precipitates**. - Inflammation affecting the lens would typically present as cataract formation or direct lens inflammation, not KPs. *Corneal stroma* - The **corneal stroma** is the thickest layer of the cornea and is primarily composed of collagen fibrils and keratocytes. - While inflammation can affect the stroma (e.g., in stromal keratitis), **keratic precipitates** specifically form on the **innermost layer**, the endothelium, facing the anterior chamber.

Question 353: A 20-year-old male complains of repeated changes in glasses prescription. This is most likely caused by:

A. Keratoconus (Correct Answer)
B. Cataract
C. Glaucoma
D. Pathological myopia

Explanation: ***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.

Question 354: Topical steroids can be used in which of the following keratitis conditions:

A. Disciform keratitis (Correct Answer)
B. Herpetic dendritic keratitis
C. Bacterial keratitis
D. Fungal keratitis

Explanation: ***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).

Question 355: Corneal tattooing is done by ?

A. Silver nitrate
B. Gold nanoparticles
C. Titanium oxide
D. India ink (Correct Answer)

Explanation: ***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**

Question 356: Topical antiviral drugs are not indicated in:

A. Metaherpetic ulcer (Correct Answer)
B. Dendritic ulcer
C. Stromal necrotizing keratitis
D. All of the options

Explanation: ***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.

Question 357: For transplantation, cornea is preserved in:

A. Modified MK medium (Correct Answer)
B. Wet medium
C. Glycerine medium
D. All of the options

Explanation: ***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.

Question 358: Avascular structure of the eye is -

A. Retina
B. Cornea (Correct Answer)
C. Ciliary body
D. Conjunctiva

Explanation: ***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).

Question 359: Salmon patch is seen in -

A. Disciform keratitis
B. Interstitial keratitis (Correct Answer)
C. Phlyctenular keratitis
D. Acne rosacea

Explanation: **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**.

Question 360: Preferred suture for corneal graft is:

A. 10-0 nylon (Correct Answer)
B. 9-0 prolene
C. 8-0 silk
D. 7-0 vicryl

Explanation: ***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.

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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