Diseases of the Cornea Practice Questions

Q: In photophthalmia, which part of the eye is primarily affected?

Cornea. ***Cornea*** - **Photophthalmia** (also known as **snow blindness** or **arc eye**) is caused by overexposure to **ultraviolet (UV) light**, which primarily damages the **corneal epithelium**. - This damage leads to **superficial punctate keratitis**, characterized by pain, foreign body sensation, photophobia, and blurred vision. - Symptoms typically appear **6-12 hours after exposure** and resolve within **24-48 hours** with supportive care. *Retina* - The **retina** can be damaged by certain types of light (e.g., solar retinopathy from looking at the sun), but **UV light** in photophthalmia is largely absorbed by the anterior structures of the eye, particularly the cornea. - Retinal damage would typically present with **central visual loss** or **scotomas**, differing from the acute pain and photophobia of photophthalmia. *Optic nerve* - The **optic nerve** transmits visual information from the retina to the brain and is generally not directly affected by **UV light exposure** causing photophthalmia. - Optic nerve issues would manifest as severe **vision loss**, **pupillary abnormalities**, or **pain with eye movement**, which are not typical for photophthalmia. *Lens* - While chronic **UV exposure** can contribute to **cataract formation** in the lens over time, this is a long-term effect, not the acute primary damage seen in photophthalmia. - The acute presentation of photophthalmia with severe pain, photophobia, and foreign body sensation is characteristic of **corneal epithelial damage**, not lens involvement.

Q: Keratitis in contact lens wearers is caused by all except?

Pneumococcus. ***Pneumococcus*** - While *Streptococcus pneumoniae* (Pneumococcus) can cause bacterial keratitis, it is **classically associated with corneal ulcers following trauma** rather than contact lens wear. - In contact lens-related keratitis, Pneumococcus is **significantly less common** compared to *Pseudomonas*, which dominates as the primary bacterial pathogen in this setting. - Pneumococcal keratitis typically presents with a **well-demarcated, dense purulent ulcer with hypopyon**, often following corneal injury. *Pseudomonas* - **_Pseudomonas aeruginosa_** is **the most common cause of bacterial keratitis in contact lens wearers**, accounting for the majority of severe cases. - It thrives in moist environments such as contaminated contact lens cases and solutions, producing **exotoxins and proteases that cause rapid corneal destruction and tissue melt**. - Presents with a **rapidly progressive, dense stromal infiltrate** with a characteristic **ground-glass appearance** and potential for perforation. *Aspergillus* - **_Aspergillus_ species** are an important cause of **fungal keratitis**, particularly associated with contact lens wear, poor lens hygiene, and contaminated lens solutions. - Fungal keratitis presents with **feathery-edged infiltrates, satellite lesions**, and ring-shaped infiltrates, often requiring antifungal therapy. - More common in tropical climates and agricultural settings. *Chlamydia* - **_Chlamydia trachomatis_** is primarily a cause of **trachoma** (chronic follicular conjunctivitis leading to scarring) and **adult inclusion conjunctivitis**. - While it can cause **superficial punctate keratitis and pannus formation** in trachoma, it is **NOT a typical cause of acute suppurative keratitis in contact lens wearers**. - The acute bacterial and fungal keratitis seen in contact lens wearers is a different clinical entity from chlamydial conjunctivitis/keratopathy.

Q: Which of the following statements about Fuchs' corneal dystrophy is incorrect?

Unilateral condition. ***Unilateral condition - INCORRECT STATEMENT*** - **Fuchs' corneal dystrophy** is typically a **bilateral condition**, although it can be asymmetric in its presentation. - The disease often affects both eyes, progressing from early morning blurriness to constant visual impairment. - This is the INCORRECT statement - Fuchs' is NOT unilateral. *Posterior dystrophy - Correct statement* - **Fuchs' corneal dystrophy** is classified as a posterior corneal dystrophy, meaning it primarily affects the **corneal endothelium** and Descemet's membrane. - This posterior involvement leads to the characteristic guttata and corneal edema. *Endothelial dystrophy - Correct statement* - It is fundamentally an **endothelial dystrophy**, resulting from primary dysfunction and loss of corneal endothelial cells. - The compromised endothelial pump function leads to **stromal edema** and reduced visual acuity. *Occurs in old age - Correct statement* - Fuchs' corneal dystrophy typically presents in **middle to old age**, with symptoms often becoming noticeable in individuals over 50. - While congenital forms of corneal dystrophy exist, Fuchs' is not usually one of them.

Q: Which agent is known to cause corneal ulcers that may resemble fungal infections?

Nocardia asteroides. ***Nocardia asteroides*** - This organism can cause **Nocardia keratitis**, which often presents with a **feathery or crystalline appearance** in the cornea, mimicking a fungal infection. - It tends to occur in patients with **contact lens use** or ocular trauma and requires specific antimicrobial treatment different from fungal therapy. *Mycobacterium* - **Atypical mycobacteria** can cause chronic, indolent corneal ulcers, particularly after trauma or surgery. - While they can be challenging to diagnose, their appearance typically differs from the **feathery morphology** associated with fungal or Nocardia infections. *Klebsiella pneumoniae* - **Klebsiella pneumoniae** is a common cause of **bacterial keratitis**, especially in contact lens wearers. - Infections usually manifest as a rapidly progressing infiltrate with significant inflammation and often produce abundant **mucopurulent discharge**, not typically mistaken for fungal infections. *Chlamydia trachomatis* - **Chlamydia trachomatis** is the causative agent of **trachoma**, leading to recurrent conjunctivitis and eventually corneal scarring and blindness in endemic areas. - It does not cause acute corneal ulcers that resemble fungal infections; rather, it results in a chronic inflammatory process with **follicular conjunctivitis** and **pannus formation**.

Q: What condition is associated with copper deposition in the cornea?

Wilson's disease. ***Wilson's disease*** - Wilson's disease is a genetic disorder of **copper metabolism** leading to excess copper accumulation in various tissues, including the cornea [1]. - This copper deposition in the posterior Descemet's membrane of the cornea forms a distinctive golden-brown or greenish-brown ring known as the **Kayser-Fleischer ring**. *Keratoconus* - This condition is characterized by progressive thinning and steepening of the cornea, causing it to bulge into a **cone-like shape**. - It primarily affects vision due to irregular astigmatism and does not involve copper deposition. *Keratoglobus* - Keratoglobus is a rare corneal ectatic disorder where the entire cornea is thinned and bulges forward, giving it a **globe-like appearance**. - It is congenital and typically runs in families, and it is not associated with copper deposition. *Siderosis* - Siderosis refers to the deposition of **iron** in various tissues, often due to chronic hemorrhage or metallic foreign bodies. - In the eye, it can occur after intraocular iron foreign bodies, leading to retinal degeneration and other ocular complications, but it does not involve copper.

Q: What is the most common infection in contact lens users?

Pseudomonas. ***Pseudomonas*** - **Pseudomonas aeruginosa** is the leading cause of **bacterial keratitis** in contact lens wearers, accounting for 60-70% of culture-positive cases - This bacterium can **adhere to lenses**, form **biofilms**, and thrive in moist lens storage cases - Can cause rapid and severe corneal damage with **corneal ulceration**, potentially leading to **vision loss** *Staphylococcus* - **Staphylococcus aureus** and **Staphylococcus epidermidis** are common commensals of the skin and can cause eye infections, including keratitis and blepharitis - However, in the context of contact lens-related keratitis, **Pseudomonas aeruginosa** remains the primary pathogen for severe corneal infections *Streptococcus* - While various **Streptococcus species** (especially S. pneumoniae) can cause bacterial keratitis, they are less commonly associated with contact lens-related keratitis compared to Pseudomonas - **Streptococcal keratitis** typically occurs in non-contact lens wearers or after trauma *Neisseria* - **Neisseria gonorrhoeae** can cause hyperacute bacterial conjunctivitis with severe purulent discharge, but is not the most common cause of contact lens-related keratitis - **Neisseria meningitidis** can rarely cause conjunctivitis, but these infections usually indicate specific exposure or systemic disease

Q: Krukenberg spindles -

Involve posterior surface of cornea. **Involve posterior surface of cornea** - **Krukenberg spindles** are vertical, spindle-shaped deposits of **pigment (melanin)** on the posterior surface of the cornea. - They are a characteristic finding in **pigment dispersion syndrome** and **pigmentary glaucoma**, where iris pigment is released and circulated in the aqueous humor, eventually depositing on the corneal endothelium. *Involve anterior surface of cornea* - Deposits on the anterior corneal surface are less common and typically indicate external factors or specific corneal dystrophies, not Krukenberg spindles. - **Krukenberg spindles** are specifically formed by pigment circulating within the anterior chamber, which deposits on the posterior corneal surface due to aqueous humor flow. *Involve anterior lens surface* - Pigment deposits can occur on the anterior lens capsule, but these are typically diffuse or in a "bull's eye" pattern and are not referred to as **Krukenberg spindles**. - **Krukenberg spindles** are defined by their specific "spindle" shape and location on the cornea. *Involve posterior surface of lens* - Deposits on the posterior lens surface are usually associated with specific conditions like **uveitis** (posterior synechiae) or related to retinal issues, not pigment dispersion syndrome or **Krukenberg spindles**. - The formation of **Krukenberg spindles** is directly linked to the flow of aqueous humor and gravity affecting pigment particles in the anterior chamber.

Q: In specular microscopy endothelial density is measured by?

Fixed frame analysis. ***Fixed frame analysis*** - This is the **standard method** used in specular microscopy to measure corneal endothelial cell density. - It involves analyzing a specific, fixed area of the **endothelial mosaic** and counting the number of cells within that defined frame. - The cell count from this fixed area is then **extrapolated** to calculate the overall endothelial cell density (cells/mm²). - This technique provides **quantitative assessment** of endothelial health, which is crucial for evaluating corneal function and pre-operative assessment for intraocular surgeries. *Optical doubling* - This is not a standard method for measuring endothelial density in specular microscopy. - Optical doubling relates to **refractive phenomena** or optical measurement techniques used in other contexts, not for endothelial cell counting. *Optical focusing* - While **essential for image acquisition**, optical focusing is merely a preliminary step to obtain a clear, sharp image of the endothelium. - It does not measure or count cells; it only ensures proper visualization before analysis. - The actual measurement requires subsequent **cell counting methods** like fixed frame analysis. *None of the options* - Incorrect because **fixed frame analysis** is indeed the recognized and widely used method for measuring endothelial density in specular microscopy.

Q: The immune ring is a feature associated with which condition?

Fungal corneal ulcer. ***Fungal corneal ulcer*** - The **immune ring** (also known as a **Wessely ring**) is a characteristic sign seen in **fungal corneal ulcers**, particularly those caused by filamentous fungi. - It represents a **circumferential infiltrate** of immune cells and antigen-antibody complexes. *Interstitial keratitis* - Characterized by **stromal inflammation** without primary involvement of the epithelium or endothelium, often leading to ghost vessels after treatment. - It is typically associated with conditions like **syphilis** or other systemic infections, not an immune ring. *Bacterial corneal ulcer* - Often presents with a **rapidly progressing** corneal infiltrate, significant pain, and sometimes **hypopyon**. - While an immune response occurs, it does not typically form a distinct, well-defined **immune ring** like in fungal infections. *Herpes simplex keratitis* - Classically manifests as a **dendritic ulcer** or geographic ulcer, which can progress to stromal keratitis. - The immune ring is **not a feature** of herpes simplex keratitis; distinctive patterns like dendrites or disciform keratitis are seen.

Q: Corneal tattooing is done by ?

India ink. ***India ink*** - **India ink (carbon black)** is the traditional and most commonly used pigment for corneal tattooing due to its stable black color and inert properties. - It is applied to the **corneal stroma** to mask corneal opacities or for cosmetic purposes in cases of unsightly leucomatous corneal scars. - India ink has been the **gold standard** for corneal tattooing since the 19th century. *Gold chloride* - While **gold preparations** (including platinum-gold) have been used historically for corneal tattooing, they are much less common than India ink. - Gold chloride specifically is not the standard or preferred agent for this procedure. - India ink remains the pigment of choice due to better cosmetic results and established safety profile. *Titanium chloride* - **Titanium chloride** is a corrosive chemical and is not used in corneal tattooing; its application would cause severe damage to the delicate corneal tissue. - It is primarily used in industrial applications and chemical synthesis, not in ophthalmic procedures. *Aluminium chloride* - **Aluminium chloride** is an astringent and antiseptic, often used in dermatological products, but it is not a tattooing pigment for the cornea. - Its chemical properties would be highly irritating to the eye and potentially damaging to corneal cells.

Question 1

In photophthalmia, which part of the eye is primarily affected?

Accepted Answer

Cornea

Answer

Lens

Answer

Retina

Answer

Optic nerve

Question 2

Keratitis in contact lens wearers is caused by all except?

Accepted Answer

Pneumococcus

Answer

Chlamydia

Answer

Aspergillus

Answer

Pseudomonas

Question 3

Which of the following statements about Fuchs' corneal dystrophy is incorrect?

Accepted Answer

Unilateral condition

Answer

Endothelial dystrophy

Answer

Occurs in old age

Answer

Posterior dystrophy

Question 4

Which agent is known to cause corneal ulcers that may resemble fungal infections?

Accepted Answer

Nocardia asteroides

Answer

Mycobacterium

Answer

Klebsiella pneumoniae

Answer

Chlamydia trachomatis

Question 5

What condition is associated with copper deposition in the cornea?

Accepted Answer

Wilson's disease

Answer

Keratoglobus

Answer

Keratoconus

Answer

Siderosis

Question 6

What is the most common infection in contact lens users?

Accepted Answer

Pseudomonas

Answer

Streptococcus

Answer

Staphylococcus

Answer

Neisseria

Question 7

Krukenberg spindles -

Accepted Answer

Involve posterior surface of cornea

Answer

Involve anterior surface of cornea

Answer

Involve anterior lens surface

Answer

Involve posterior surface of lens

Question 8

In specular microscopy endothelial density is measured by?

Accepted Answer

Fixed frame analysis

Answer

None of the options

Answer

Optical doubling

Answer

Optical focusing

Question 9

The immune ring is a feature associated with which condition?

Accepted Answer

Fungal corneal ulcer

Answer

Interstitial keratitis

Answer

Bacterial corneal ulcer

Answer

Herpes simplex keratitis

Question 10

Corneal tattooing is done by ?

Accepted Answer

India ink

Answer

Titanium chloride

Answer

Aluminium chloride

Answer

Gold chloride

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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