Diseases of the Cornea Practice Questions

Q: Acute corneal hydrops is seen in:

Keratoconus. ***Keratoconus*** - **Acute corneal hydrops** is a classic complication of advanced **keratoconus**, occurring when a break in **Descemet's membrane** allows aqueous humor to enter the corneal stroma. - This leads to sudden onset of **corneal edema**, pain, and significant vision loss, often presenting with a milky white cornea due to stromal clouding. *Corneal dystrophy* - **Corneal dystrophies** are a group of genetic disorders that affect the clarity and structure of the cornea, typically causing progressive vision loss or recurrent epithelial erosions. - While some dystrophies can lead to corneal edema, **acute hydrops** specifically due to a Descemet's membrane rupture is not a characteristic feature. *Anterior staphyloma* - An **anterior staphyloma** is a bulging scar of the cornea and sclera, usually resulting from severe thinning or perforation, often associated with elevated intraocular pressure. - It is a structural deformation involving the entire globe's anterior segment, distinct from the sudden stromal edema of **corneal hydrops** caused by Descemet's rupture. *Interstitial keratitis* - **Interstitial keratitis** is characterized by non-ulcerative inflammation of the corneal stroma without primary involvement of the epithelium or endothelium, often associated with systemic infections like syphilis or Lyme disease. - It typically results in stromal opacification and vascularization ("salmon patch") but does not involve the acute rupture of Descemet's membrane seen in **hydrops**.

Q: Which is an emergency therapeutic indication of keratoplasty?

Perforated corneal ulcer. ***Perforated corneal ulcer*** - A **perforated corneal ulcer** is an ocular emergency requiring urgent intervention to restore the integrity of the globe and prevent severe vision loss or endophthalmitis. Keratoplasty, in this context, acts as a tectonic graft to seal the perforation. - The emergent nature stems from the high risk of **intraocular infection** and **collapse of the anterior chamber**, which can lead to permanent damage and vision impairment. *Keratoconus* - While severe **keratoconus** can eventually lead to keratoplasty, it is typically an elective procedure performed to improve vision after other treatments like contact lenses are no longer effective. - It is a **slowly progressive condition** that does not usually pose an immediate threat to ocular integrity unless acute hydrops occurs, which itself may require different acute management. *Myopia* - **Myopia**, or nearsightedness, is a refractive error typically corrected with glasses, contact lenses, or elective refractive surgery (e.g., LASIK). - It is not a condition that warrants a **therapeutic or emergency keratoplasty**, as it does not involve structural compromise or disease of the cornea that would necessitate transplantation. *Hypermetropia* - **Hypermetropia**, or farsightedness, is also a refractive error, managed with corrective lenses or elective refractive surgery. - Similar to myopia, it does not involve a corneal disease process that would necessitate a **keratoplasty**, especially not on an emergency basis.

Q: The primary indication for collagen cross-linking is:

Keratoconus. ***Keratoconus*** - *Keratoconus* is a progressive disorder causing corneal thinning and a conical shape, leading to vision distortion. - *Collagen cross-linking (CXL)* is primarily indicated to halt the progression of keratoconus by strengthening corneal collagen fibers through riboflavin and UV-A light exposure. - This is the **most common and primary indication** for CXL, as it is FDA-approved and evidence-based for progressive keratoconus. *Pellucid marginal degeneration* - Pellucid marginal degeneration (PMD) involves a band of corneal thinning, usually in the inferior periphery, causing high astigmatism. - While CXL can be considered, PMD is less common and often managed with contact lenses or surgical techniques like crescentic resection. *Corneal ectasia after refractive surgery* - Corneal ectasia after refractive surgery is a complication where the cornea thins and bulges following procedures like LASIK. - CXL can be used to stabilize this condition, but it is a secondary indication, as keratoconus is the most common primary ectatic disease. *Progressive corneal ectasia* - Progressive corneal ectasia is a broad term describing any corneal thinning and bulging that worsens over time. - While keratoconus is a form of progressive corneal ectasia, the question asks for the primary indication, which points to the most common specific condition.

Q: Which of the following organisms can penetrate a normal intact cornea?

Gonococcus. ***Gonococcus*** - *Neisseria gonorrhoeae* is unique among bacteria in its ability to directly penetrate the **intact corneal epithelium**. - This characteristic makes it a highly virulent cause of **rapidly progressive corneal ulceration** and endophthalmitis, especially in neonates born to infected mothers. *Staphylococcus aureus* - *Staphylococcus aureus* typically requires some form of **corneal epithelial defect** (e.g., abrasion, foreign body) to invade and cause keratitis. - While it is a common cause of bacterial keratitis, it does not penetrate an **undamaged cornea**. *Streptococcus pneumoniae* - Similar to *S. aureus*, *Streptococcus pneumoniae* usually needs a **breach in the corneal epithelium** to establish an infection. - It is a frequent cause of **bacterial conjunctivitis** and keratitis but is not known for invading an intact cornea. *Listeria monocytogenes* - *Listeria monocytogenes* is an important human pathogen but is primarily known for causing **meningitis, sepsis, and perinatal infections**. - It is not a common cause of bacterial keratitis, and there is no evidence to suggest it can penetrate an **intact corneal surface**.

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

It is a type of endothelial dystrophy. ***It is a type of endothelial dystrophy*** - **Fuchs' endothelial corneal dystrophy (FECD)** is the **classic posterior/endothelial corneal dystrophy**, classified in the **IC3D classification system** as a primary endothelial dystrophy. - It involves **progressive loss of corneal endothelial cells** and formation of **guttata** (excrescences in Descemet's membrane), leading to endothelial dysfunction. - The dysfunctional endothelium cannot maintain corneal deturgescence, resulting in **corneal edema** and eventually **bullous keratopathy** in advanced cases. *It is characterized by bilateral involvement* - While Fuchs' dystrophy is **typically bilateral**, it can be **asymmetric** in presentation and progression. - Bilaterality is a common feature but not the most defining characteristic of the disease. *It primarily occurs in older adults* - Fuchs' dystrophy typically manifests in **middle age (40s-50s)** and progresses with age. - However, the condition has a **genetic basis** and cellular changes begin earlier than symptom onset. - Symptomatic disease is more common in older adults, but this doesn't define the disease entity itself. *Glaucoma is not a common association* - Studies have shown **increased prevalence of glaucoma** in patients with Fuchs' dystrophy compared to the general population. - The association may relate to **endothelial dysfunction** affecting aqueous outflow or shared risk factors. - This statement is **false** - glaucoma association has been documented.

Q: What is the most effective treatment for central nebular corneal opacity?

Phototherapeutic keratectomy. ***Phototherapeutic keratectomy*** - **Phototherapeutic keratectomy (PTK)** is the most effective treatment for superficial **central nebular corneal opacities** as it uses an excimer laser to remove anterior corneal tissue with precision. - This **surgical procedure** aims to improve visual acuity by reducing the opacity's density while preserving the main corneal structure. - PTK is preferred over more invasive procedures for superficial opacities. *Penetrating keratoplasty* - **Penetrating keratoplasty (PK)**, or full-thickness corneal transplant, is reserved for **deep stromal opacities** or those that significantly impair vision beyond the scope of PTK. - This **surgical procedure** involves replacing the entire central cornea, which carries higher risks such as graft rejection and requires longer recovery compared to PTK. *Gas permeable contact lens* - **Gas permeable (GP) contact lenses** are used for correcting irregular astigmatism and improving visual acuity in cases of mild corneal surface irregularities. - They provide a smooth refracting surface but do not address the underlying pathology of the opacity and are not effective for treating dense central opacities. *Soft contact lens* - **Soft contact lenses** are primarily used for correcting refractive errors like myopia, hyperopia, and astigmatism, or for therapeutic purposes such as protecting the ocular surface. - They are generally not effective in improving vision significantly in the presence of a central corneal opacity, as they conform to the corneal shape and do not mask the opacity.

Q: What does the hypopyon in a fungal corneal ulcer contain?

Purulent material. ***Purulent material*** - A **hypopyon** is an accumulation of **inflammatory cells** (primarily neutrophils) and fibrin in the anterior chamber of the eye. - In a fungal corneal ulcer, this material is **purulent** (pus) due to the severe inflammatory response triggered by the fungal infection. *Fungal filaments* - While fungal filaments (hyphae) are the causative agents of the infection and are present within the corneal tissue, they do not typically form the bulk of the **hypopyon** in the anterior chamber. - The hypopyon represents the host's inflammatory response rather than the direct fungal elements. *Fungal spores* - Similar to fungal filaments, **spores** are fungal reproductive structures and are found within the infected cornea, not as the primary component of the anterior chamber hypopyon. - The inflammatory exudate is composed of immune cells responding to the infection. *Sterile material* - A **hypopyon** associated with an active infection, such as a fungal corneal ulcer, is by definition **not sterile**. - It contains immune cells and inflammatory mediators, and often live microorganisms or their products, forming pus.

Q: All are corneal signs of trachoma except which of the following?

Conjunctival follicles. ***Conjunctival follicles*** - While **conjunctival follicles** are a hallmark sign of trachoma, they are located on the **conjunctiva**, not directly on the cornea. - These follicles represent collections of lymphocytes in the subconjunctival tissue, particularly in the **tarsal conjunctiva**. *Corneal opacity* - **Corneal opacity** is a late-stage complication of trachoma, resulting from chronic inflammation and scarring. - It significantly impairs vision and can lead to blindness, being a direct corneal involvement. *Pannus* - **Pannus** is the invasion of the cornea by blood vessels and fibrous tissue, often starting at the superior limbus. - It is a characteristic corneal sign of chronic trachoma, indicating corneal inflammation and neovascularization. *Corneal scarring* - **Corneal scarring** is a severe and irreversible consequence of chronic trachoma, often following repeated episodes of infection and inflammation. - It primarily results from the healing of corneal ulcers and the breakdown of Bowman's layer in the cornea.

Q: Which of the following is not a typical sign of Herpes simplex involvement of the eye?

Purulent discharge. ***Purulent discharge*** - **Herpes simplex virus (HSV)** infections of the eye, whether **keratitis** or **conjunctivitis**, typically do **not** cause a **purulent (pus-like) discharge**. - **Purulent discharge** is more characteristic of acute **bacterial conjunctivitis**. *Corneal anaesthesia* - **Corneal nerve damage** is a common and characteristic feature of chronic or recurrent **herpetic keratitis**. - This can lead to **reduced corneal sensation**, making the eye more vulnerable to further injury. *Iridocyclitis* - **Iridocyclitis** (inflammation of the **iris** and **ciliary body**) can occur as a complication of intraocular anterior **uveitis** in **Herpes simplex eye infections**. - It often leads to symptoms like **pain**, **photophobia**, and **blurred vision**. *Vesicular lesions* - **Vesicular lesions** on the **eyelids** or around the eye (HSV **blepharitis** or **dermatitis**) are typical during the primary or recurrent outbreaks of **Herpes simplex infections**. - These lesions contain **infectious virus** and can shed, potentially leading to **corneal involvement**.

Q: Corneal endothelial cell count is done by:

Specular microscopy. ***Specular microscopy*** - **Specular microscopy** is the gold standard for **non-invasive quantitative and qualitative analysis** of the corneal endothelium. - It uses reflected light to visualize and count individual endothelial cells, providing critical information about cell density, morphology, and polymegethism. *Keratometry* - **Keratometry** measures the **curvature of the anterior corneal surface**, primarily used to assess corneal astigmatism and fit contact lenses. - It does not provide information about the **endothelial cell layer**. *Gonioscopy* - **Gonioscopy** is a clinical technique used to **visualize the anterior chamber angle** of the eye. - It is crucial for diagnosing and classifying glaucoma but does not evaluate the **corneal endothelium**. *Slit lamp* - A **slit lamp** provides a magnified view of the anterior and posterior segments of the eye for general examination. - While it can help identify gross corneal abnormalities, it is **not precise enough** to quantify or qualitatively assess individual endothelial cells in detail.

Question 1

Acute corneal hydrops is seen in:

Accepted Answer

Keratoconus

Answer

Corneal dystrophy

Answer

Anterior staphyloma

Answer

Interstitial keratitis

Question 2

Which is an emergency therapeutic indication of keratoplasty?

Accepted Answer

Perforated corneal ulcer

Answer

Keratoconus

Answer

Myopia

Answer

Hypermetropia

Question 3

The primary indication for collagen cross-linking is:

Accepted Answer

Keratoconus

Answer

Pellucid marginal degeneration

Answer

Corneal ectasia after refractive surgery

Answer

Progressive corneal ectasia

Question 4

Which of the following organisms can penetrate a normal intact cornea?

Accepted Answer

Gonococcus

Answer

Staphylococcus aureus

Answer

Streptococcus pneumoniae

Answer

Listeria monocytogenes

Question 5

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

Accepted Answer

It is a type of endothelial dystrophy

Answer

Glaucoma is not a common association.

Answer

It is characterized by bilateral involvement

Answer

It primarily occurs in older adults

Question 6

What is the most effective treatment for central nebular corneal opacity?

Accepted Answer

Phototherapeutic keratectomy

Answer

Penetrating keratoplasty

Answer

Gas permeable contact lens

Answer

Soft contact lens

Question 7

What does the hypopyon in a fungal corneal ulcer contain?

Accepted Answer

Purulent material

Answer

Fungal spores

Answer

Sterile material

Answer

Fungal filaments

Question 8

All are corneal signs of trachoma except which of the following?

Accepted Answer

Conjunctival follicles

Answer

Corneal opacity

Answer

Pannus

Answer

Corneal scarring

Question 9

Which of the following is not a typical sign of Herpes simplex involvement of the eye?

Accepted Answer

Purulent discharge

Answer

Corneal anaesthesia

Answer

Iridocyclitis

Answer

Vesicular lesions

Question 10

Corneal endothelial cell count is done by:

Accepted Answer

Specular microscopy

Answer

Keratometry

Answer

Gonioscopy

Answer

Slit lamp

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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