Diseases of the Cornea — MCQs
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Scissor reflex is seen in ?
The immune ring is a feature associated with which condition?
Interstitial keratitis is associated with all of the following except:
Which agent is known to cause corneal ulcers that may resemble fungal infections?
Corneal sensations are decreased in all of the following conditions except:
Non-sterile hypopyon is seen in ?
In specular microscopy endothelial density is measured by?
Schwalbe's ring is seen in which layer of the cornea?
Krukenberg spindles -
Reis-Buckler dystrophy affects which layer of the cornea?
Diseases of the Cornea Indian Medical PG Practice Questions and MCQs
Question 391: Scissor reflex is seen in ?
- A. Open angle glaucoma
- B. Phlyctenular conjunctivitis
- C. Keratoconus (Correct Answer)
- D. Interstitial keratitis
Explanation: ***Keratoconus*** - The **scissor reflex**, or **scissoring reflex**, is a characteristic finding during **retinoscopy** in patients with **keratoconus**. - It is caused by the irregular and variable refractive power across the cornea, leading to a distorted red reflex that appears to split into two bands moving in opposite directions. *Open angle glaucoma* - **Open-angle glaucoma** is characterized by progressive damage to the **optic nerve** and visual field loss, typically with a normal open anterior chamber angle. - It does not involve abnormalities in corneal shape or light refraction that would produce a scissor reflex during retinoscopy. *Phlyctenular conjunctivitis* - **Phlyctenular conjunctivitis** is an inflammatory condition characterized by small nodular lesions (phlyctenules) on the conjunctiva or cornea, often associated with a hypersensitivity reaction to microbial antigens. - This condition primarily affects the surface of the eye and does not cause the corneal ectasia or irregular astigmatism seen in keratoconus. *Interstitial keratitis* - **Interstitial keratitis** is an inflammation of the corneal stroma without significant involvement of the epithelium or endothelium, often associated with systemic infections like syphilis or Lyme disease. - While it can cause corneal opacification and vision loss, it typically does not lead to the conical shape or irregular astigmatism characteristic of keratoconus, which produces the scissor reflex.
Question 392: The immune ring is a feature associated with which condition?
- A. Interstitial keratitis
- B. Bacterial corneal ulcer
- C. Herpes simplex keratitis
- D. Fungal corneal ulcer (Correct Answer)
Explanation: ***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 393: Interstitial keratitis is associated with all of the following except:
- A. Syphilis
- B. Acanthamoeba (Correct Answer)
- C. Chlamydia Trachomatis
- D. Herpes Zoster Virus (HZV)
Explanation: ***Acanthamoeba*** - **Acanthamoeba keratitis** is a **suppurative keratitis** characterized by a painful, ring-shaped infiltrate with epithelial ulceration, typically associated with contact lens use and contaminated water exposure. - It causes **ulcerative stromal inflammation**, not the **non-ulcerative deep stromal inflammation** that characterizes classic interstitial keratitis. - **This is NOT a cause of interstitial keratitis.** *Syphilis* - **Congenital syphilis** is the **CLASSIC cause** of bilateral **interstitial keratitis**, often presenting in late childhood with "salmon patch" appearance, photophobia, lacrimation, and eventual ghost vessels. - The inflammation is **non-ulcerative and chronic**, affecting the **deep corneal stroma** with preservation of epithelium. - This is the most important association with interstitial keratitis to remember. *Chlamydia Trachomatis* - **Chlamydia trachomatis** causes **trachoma**, a chronic keratoconjunctivitis leading to **superficial keratitis with pannus formation** (superficial vascularization from the limbus). - The corneal involvement in trachoma is **superficial**, not the deep stromal inflammation seen in classic interstitial keratitis. - While listed in some references, **Chlamydia is NOT a standard cause of interstitial keratitis** in major ophthalmology textbooks. - **Note:** This option is potentially debatable, but Acanthamoeba is the more definitively incorrect answer. *Herpes Zoster Virus (HZV)* - **Herpes zoster ophthalmicus** can lead to **interstitial keratitis** and **disciform keratitis** (immune-mediated stromal inflammation with disc-shaped corneal edema). - Similarly, **HSV (Herpes Simplex Virus)** causes stromal keratitis, a form of interstitial keratitis. - The corneal involvement includes **deep stromal inflammation, scarring**, and potential neurotrophic changes leading to vision impairment.
Question 394: Which agent is known to cause corneal ulcers that may resemble fungal infections?
- A. Nocardia asteroides (Correct Answer)
- B. Mycobacterium
- C. Klebsiella pneumoniae
- D. Chlamydia trachomatis
Explanation: ***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**.
Question 395: Corneal sensations are decreased in all of the following conditions except:
- A. Neuroparalytic keratitis
- B. Leprosy
- C. Herpetic keratitis
- D. Recurrent corneal erosion syndrome (Correct Answer)
Explanation: ***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.
Question 396: Non-sterile hypopyon is seen in ?
- A. Fungal infection (Correct Answer)
- B. Pneumococcal infection
- C. Pseudomonas aeruginosa infection
- D. Gonococcal conjunctivitis
Explanation: ***Fungal infection*** - **Fungal keratitis** produces a **non-sterile hypopyon**, meaning the hypopyon contains actual fungal elements and organisms, not just inflammatory cells alone. - This is characteristically seen with **filamentous fungi** (Aspergillus, Fusarium) and yeast (Candida), which can directly invade the anterior chamber. - The hypopyon is typically **indolent, greyish-white, and does not shift with position** unlike bacterial hypopyon, and shows poor response to antibacterial therapy. - **Fungal culture and KOH mount** are diagnostic. *Pneumococcal infection* - **Bacterial keratitis** caused by *Streptococcus pneumoniae* produces a **sterile hypopyon** consisting purely of inflammatory cells (polymorphonuclear leukocytes) without organisms in the anterior chamber. - Presents with **acute onset, severe pain, and rapid progression** with a dense stromal infiltrate. - The hypopyon is **white, mobile, and shifts with head position**. *Pseudomonas aeruginosa infection* - **Pseudomonas keratitis** causes an aggressive infection with a **sterile hypopyon** due to intense inflammatory response. - Characterized by **rapidly progressive stromal necrosis** with a ground-glass appearance and greenish discharge. - Often associated with **contact lens wear** and can lead to corneal perforation within 24-48 hours. *Gonococcal conjunctivitis* - **Neisseria gonorrhoeae conjunctivitis** causes severe **hyperacute purulent conjunctivitis** with copious discharge. - Typically does **not cause hypopyon** unless there is secondary corneal ulceration leading to keratitis or endophthalmitis. - Primary manifestation is conjunctival inflammation, chemosis, and lid edema.
Question 397: In specular microscopy endothelial density is measured by?
- A. None of the options
- B. Optical doubling
- C. Fixed frame analysis (Correct Answer)
- D. Optical focusing
Explanation: ***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.
Question 398: Schwalbe's ring is seen in which layer of the cornea?
- A. Bowman's membrane
- B. Stroma
- C. Substantia propria
- D. Descemet's membrane (Correct Answer)
Explanation: ***Descemet's membrane*** - Schwalbe's ring is a circular opacity representing the termination of **Descemet's membrane** at the periphery of the cornea, just anterior to the **trabecular meshwork**. - Its presence is a normal anatomical variant, but prominence can be associated with certain conditions like **posterior embryotoxon**. *Bowman's membrane* - This layer is found immediately beneath the **corneal epithelium** and does not extend to form Schwalbe's ring. - It is an acellular layer composed of collagen fibrils randomly arranged, offering resistance to infection and injury. *Stroma* - The stroma is the thickest layer of the cornea, composed primarily of **collagen lamellae** arranged in a highly organized manner. - It lies posterior to Bowman's membrane and anterior to Descemet's membrane, but its termination does not form Schwalbe's ring. *Substantia propria* - This is another name for the **corneal stroma**, which, as elaborated above, does not form Schwalbe's ring. - It comprises about 90% of the corneal thickness and provides the cornea's structural integrity and transparency.
Question 399: Krukenberg spindles -
- A. Involve anterior surface of cornea
- B. Involve anterior lens surface
- C. Involve posterior surface of lens
- D. Involve posterior surface of cornea (Correct Answer)
Explanation: **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.
Question 400: Reis-Buckler dystrophy affects which layer of the cornea?
- A. Stroma
- B. Bowman's membrane (Correct Answer)
- C. Endothelium
- D. Epithelium
Explanation: ***Bowman's membrane*** - **Reis-Buckler dystrophy** is a type of corneal dystrophy specifically characterized by the progressive destruction and irregular regeneration of **Bowman's membrane** and the superficial stroma. - This leads to the formation of an abnormal fibrous layer that causes recurrent corneal erosions and significant visual impairment due to corneal opacification. *Epithelium* - While patients often experience recurrent **corneal erosions** involving the epithelium, the primary pathology in Reis-Buckler dystrophy affects the underlying Bowman's membrane. - The epithelial damage is secondary to the irregular surface created by the diseased Bowman's layer. *Stroma* - The **stroma** can be secondarily affected with superficial scarring and opacification in Reis-Buckler dystrophy, but the initial and primary site of pathology is Bowman's membrane. - Other dystrophies, such as macular or granular dystrophies, primarily involve the corneal stroma. *Endothelium* - The **endothelium** is not directly affected in Reis-Buckler dystrophy. - Endothelial dystrophies, such as Fuchs' endothelial dystrophy, involve the innermost layer of the cornea and lead to corneal edema.
Practice by Chapter
Corneal Anatomy and Physiology
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Bacterial Keratitis
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Viral Keratitis
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Fungal Keratitis
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Protozoan Keratitis
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Corneal Degenerations
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Corneal Dystrophies
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Keratoconus and Ectatic Disorders
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Corneal Transplantation
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Corneal Topography and Imaging
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Dry Eye Disease
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Corneal Trauma
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