Diseases of the Cornea Practice Questions

Q: Which of the following is NOT a cause of crystal keratopathy?

Diabetes. ***Diabetes*** - While diabetes can cause various ocular complications, such as **diabetic retinopathy**, **neovascular glaucoma**, and **cataracts**, it is **not associated** with crystal keratopathy. - Corneal changes in diabetes might include epithelial defects or reduced corneal sensitivity, but **not the deposition of crystalline substances in the cornea**. - **This is the correct answer** as diabetes does NOT cause crystal keratopathy. *Cystinosis* - **Cystinosis** is a metabolic disorder characterized by the accumulation of **cystine crystals** throughout the body, including the **cornea**. - These crystals can lead to significant **photophobia**, **corneal erosions**, and visual impairment, making it a **classic cause of crystal keratopathy**. - Corneal involvement typically appears in childhood with diffuse crystalline deposits. *Schnyder's Dystrophy* - **Schnyder's corneal dystrophy** is an inherited corneal dystrophy characterized by the deposition of **cholesterol and lipid crystals** in the central and peripheral cornea. - This leads to **dense corneal opacification** and can significantly impair vision over time, representing a **classic cause of crystal keratopathy**. - The cornea shows characteristic subepithelial and stromal crystal deposits. *Bietti's Crystalline Dystrophy* - **Bietti's crystalline dystrophy** is a rare, inherited chorioretinal dystrophy characterized by **crystalline deposits primarily in the retina and choroid**. - While the name suggests crystalline involvement, these crystals are predominantly **intraretinal and do NOT typically cause corneal crystal deposits**. - Therefore, Bietti's is **NOT a typical cause of crystal keratopathy** (corneal disease), though minimal peripheral corneal crystals have been rarely reported in advanced cases. - The confusion arises from the word "crystalline" in its name, but the pathology is retinal, not corneal.

Q: All of the following are true about Keratoconus, except:

Thick cornea. ***Thick cornea*** - Keratoconus is characterized by **progressive corneal thinning** and weakening, not thickening. - This corneal thinning leads to a conical protrusion, causing significant visual distortion and irregular astigmatism. *Increased curvature of cornea and Astigmatism* - Keratoconus features **increased corneal curvature** with progressive steepening into a cone-shaped configuration. - This results in **irregular astigmatism**, a hallmark feature causing distorted vision at all distances. *Astigmatism* - **Irregular astigmatism** is a cardinal feature of keratoconus due to the asymmetric corneal shape. - Causes blurred and distorted vision that is difficult to correct with spectacles alone. *Fleischer's ring* - **Fleischer's ring** is an iron deposit ring at the base of the cone in keratoconus, visible on slit-lamp examination. - It represents hemosiderin deposition in the basal epithelial cells and is a characteristic clinical sign of keratoconus.

Q: Unilateral frontal blisters with upper lid edema and conjunctivitis is seen in?

Herpes Zoster Ophthalmicus. ***Herpes Zoster Ophthalmicus*** - This condition is characterized by a **unilateral vesicular rash** (blisters) in the **trigeminal dermatome (V1)**, which includes the forehead and upper eyelid, along with significant **lid edema** and **conjunctivitis**. - **Hutchinson's sign** (lesions on the tip, side, or root of the nose) indicates a high risk of ocular involvement due to the nasociliary nerve innervation. *Acanthamoeba Keratitis* - This is an **amoebic infection** of the cornea typically associated with **contact lens wear** and often presents with severe pain and a **ring infiltrate** in the cornea. - It does not typically present with unilateral frontal blisters or significant lid edema. *Herpes Simplex* - Herpes simplex typically causes **recurrent corneal ulcers** (dendritic or geographic) and sometimes blepharitis, but not the widespread **unilateral frontal blisters** seen in the trigeminal distribution. - While it can cause conjunctivitis and lid edema, the pattern of skin lesions is the key differentiator. *Neuroparalytic Keratitis* - This condition results from **trigeminal nerve damage**, leading to corneal anesthesia and subsequent **trophic corneal ulceration**. - It presents primarily with **corneal findings** (epithelial defects, ulcers) due to impaired sensation and tear film stability, not initial vesicular skin lesions or prominent lid edema.

Q: Kayser-Fleischer ring is found in which layer of cornea?

Descemet's membrane. ***Descemet's membrane*** - Kayser-Fleischer rings are caused by **copper deposition** at the periphery of the cornea, specifically within **Descemet's membrane**. - This membrane is located between the **corneal stroma** and the **endothelium**. *Bowman's layer* - Bowman's layer is a thin, acellular layer of the cornea that lies beneath the **corneal epithelium**. - While it plays a role in corneal integrity, it is not the site of **copper deposition** in Wilson's disease. *Corneal stroma* - The corneal stroma is the thickest layer of the cornea, composed primarily of **collagen fibrils**. - Although it contains most of the corneal mass, **copper deposition** in Kayser-Fleischer rings does not specifically occur within the main stromal layer. *Endothelium* - The corneal endothelium is the innermost layer of the cornea, responsible for maintaining **corneal deturgescence**. - While it is adjacent to Descemet's membrane, the copper rings are deposited in the membrane itself, not directly in the endothelial cell layer.

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: Corneal sensations are decreased in all of the following conditions except:

Recurrent corneal erosion syndrome. ***Recurrent corneal erosion syndrome*** - This condition involves **defective adhesion** of the corneal epithelium to the underlying Bowman's layer and basement membrane, leading to sudden, severe pain upon waking. - While it causes **pain** and **epithelial defects**, it does not primarily involve nerve damage or decreased corneal sensation; rather, episodes are often very painful due to exposed nerve endings. *Herpetic keratitis* - Caused by the **herpes simplex virus (HSV)**, which can infect the trigeminal nerve and lead to **trophic changes** in the cornea. - This viral infection often results in **significant reduction** or loss of corneal sensation, making the eye more vulnerable to trauma and delayed healing. *Neuroparalytic keratitis* - This condition is also known as **neurotrophic keratitis** and results from damage to the **trigeminal nerve**, which supplies sensation to the cornea. - Loss of corneal sensation leads to impaired reflex tearing and blinking, making the cornea susceptible to epithelial breakdown and ulceration due to lack of protective mechanisms. *Leprosy* - In ocular leprosy, the **Mycobacterium leprae** directly invades the ciliary nerves, significantly impairing corneal sensation. - This reduced sensation in leprosy patients increases the risk of **corneal ulcers** and opacification due to undetected foreign bodies and trauma.

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: 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: 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.

Question 1

Which of the following is NOT a cause of crystal keratopathy?

Accepted Answer

Diabetes

Answer

Schnyder's Dystrophy

Answer

Bietti's Dystrophy

Answer

Cystinosis

Question 2

All of the following are true about Keratoconus, except:

Accepted Answer

Thick cornea

Answer

Astigmatism

Answer

Increased curvature of cornea and Astigmatism

Answer

Fleischer's ring

Question 3

A 30 year old man presents to the clinic with pain in the eye, watering, redness, and photophobia. Examination of his eyes shows circumcorneal congestion and keratic precipitates. Assertion: Keratic precipitates (KPs) are proteinaceous deposits that can occur in various patterns on the corneal endothelium. Reason: Mutton fat KPs are seen in granulomatous iridocyclitis and are composed of epithelioid cells and macrophages.

Accepted Answer

Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion

Answer

Both Assertion and Reason are true, and Reason is the correct explanation for Assertion

Answer

Assertion is true, but Reason is false

Answer

Assertion is false but reason is true

Question 4

Unilateral frontal blisters with upper lid edema and conjunctivitis is seen in?

Accepted Answer

Herpes Zoster Ophthalmicus

Answer

Herpes Simplex

Answer

Neuroparalytic Keratitis

Answer

Acanthamoeba Keratitis

Question 5

Kayser-Fleischer ring is found in which layer of cornea?

Accepted Answer

Descemet's membrane

Answer

Endothelium

Answer

Bowman's layer

Answer

Corneal stroma

Question 6

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 7

Corneal sensations are decreased in all of the following conditions except:

Accepted Answer

Recurrent corneal erosion syndrome

Answer

Neuroparalytic keratitis

Answer

Leprosy

Answer

Herpetic keratitis

Question 8

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 9

Keratitis in contact lens wearers is caused by all except?

Accepted Answer

Pneumococcus

Answer

Chlamydia

Answer

Aspergillus

Answer

Pseudomonas

Question 10

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

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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