Diseases of the Cornea Practice Questions

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: 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: 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: Non-sterile hypopyon is seen in ?

Fungal infection. ***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.

Q: Interstitial keratitis is associated with all of the following except:

Acanthamoeba. ***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.

Q: Ameboid ulcers are primarily associated with which type of corneal ulcer?

Acanthamoeba corneal ulcer. ***Acanthamoeba corneal ulcer*** - **Acanthamoeba** infections are classically associated with **ameboid ulcers** due to the movement and destructive nature of this protozoan. - This type of ulcer often presents with severe pain, disproportionate to clinical findings, and can have a **ring infiltrates** appearance. *Fungal corneal ulcer* - Fungal ulcers typically present with a **feathery border** and satellite lesions, not ameboid shapes. - They are often associated with a history of **ocular trauma** involving plant material. *Herpetic corneal ulcer* - Herpetic ulcers are characterized by a **dendritic pattern** (tree-branch-like), which is distinct from an ameboid shape. - They are caused by the **herpes simplex virus** and can lead to recurrent episodes. *Bacterial corneal ulcer* - Bacterial ulcers typically present as a **round or oval infiltrate** with stromal edema and an overlying epithelial defect. - They can progress rapidly and are not described as having an **ameboid configuration**.

Q: Scissor reflex is seen in ?

Keratoconus. ***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.

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: 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: Reis-Buckler dystrophy affects which layer of the cornea?

Bowman's membrane. ***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.

Question 1

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 2

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 3

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 4

Non-sterile hypopyon is seen in ?

Accepted Answer

Fungal infection

Answer

Pneumococcal infection

Answer

Pseudomonas aeruginosa infection

Answer

Gonococcal conjunctivitis

Question 5

Interstitial keratitis is associated with all of the following except:

Accepted Answer

Acanthamoeba

Answer

Syphilis

Answer

Chlamydia Trachomatis

Answer

Herpes Zoster Virus (HZV)

Question 6

Ameboid ulcers are primarily associated with which type of corneal ulcer?

Accepted Answer

Acanthamoeba corneal ulcer

Answer

Fungal corneal ulcer

Answer

Bacterial corneal ulcer

Answer

Herpetic corneal ulcer

Question 7

Scissor reflex is seen in ?

Accepted Answer

Keratoconus

Answer

Open angle glaucoma

Answer

Phlyctenular conjunctivitis

Answer

Interstitial 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

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

Accepted Answer

Cornea

Answer

Lens

Answer

Retina

Answer

Optic nerve

Question 10

Reis-Buckler dystrophy affects which layer of the cornea?

Accepted Answer

Bowman's membrane

Answer

Stroma

Answer

Endothelium

Answer

Epithelium

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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