Diseases of the Cornea Practice Questions

Q: Placido disc is used for diagnosing which of the following conditions?

Keratoconus. ***Keratoconus*** - A **Placido disc**, or **keratoscope**, uses concentric rings projected onto the cornea to assess its shape and detect irregularities. - In **keratoconus**, the cornea thins and protrudes into a cone-like shape, distorting the reflected rings of the Placido disc. *Uveitis* - **Uveitis** is an inflammation of the uvea, the middle layer of the eye, which is diagnosed through examination of intraocular structures and symptoms like pain, redness, and light sensitivity. - The **Placido disc** is not used for diagnosing intraocular inflammation but rather for assessing corneal surface abnormalities. *Retinoblastoma* - **Retinoblastoma** is a malignant tumor of the retina, typically diagnosed with ophthalmoscopy (to visualize the retina), imaging studies (like ultrasound or MRI), and genetic testing. - The **Placido disc** examines the corneal surface and has no role in detecting retinal tumors. *Retinal detachment* - **Retinal detachment** involves the separation of the retina from its underlying support structures, diagnosed through ophthalmoscopy to visualize the detached retina. - The **Placido disc** evaluates the cornea, not the retina, and therefore cannot diagnose retinal detachment.

Q: Topical antifungal of choice for Aspergillus infection of the eye?

Natamycin. ***Natamycin*** - **Natamycin (Natacyn) 5%** is the **only FDA-approved topical antifungal** for ophthalmic use and is the **drug of choice** for fungal keratitis caused by filamentous fungi, including *Aspergillus*. - It is a **polyene antifungal** with excellent activity against *Aspergillus* species and has **good corneal penetration** when applied topically. - Natamycin is considered the **gold standard** for treating *Aspergillus* keratitis and is the **first-line agent** for this condition. *Fluconazole* - **Fluconazole** is a triazole antifungal with **poor activity against *Aspergillus* species**. - It is primarily effective against yeasts like *Candida* species, not filamentous fungi. - Fluconazole has **limited role** in treating *Aspergillus* eye infections and is NOT used as a topical agent for this indication. *Miconazole* - **Miconazole** is an imidazole antifungal with limited use in ophthalmic infections. - It has **poor ocular penetration** and is not considered a first-line agent for *Aspergillus* keratitis. *Clotrimazole* - **Clotrimazole** is primarily used for cutaneous and superficial fungal infections. - It has **limited systemic absorption and poor ocular penetration**, making it unsuitable for *Aspergillus* eye infections. - It is not routinely used as a topical ophthalmic antifungal agent.

Q: All are true about Bullous keratopathy except which of the following?

Seen in Macular dystrophy. ***Seen in Macular dystrophy*** - **Bullous keratopathy** is a condition caused by endothelial dysfunction leading to corneal edema and bullae formation. - While macular corneal dystrophy is a condition characterized by corneal clouding due to mucopolysaccharide deposits in the stroma, it typically does not directly cause bullous keratopathy. *Treatment is lamellar keratoplasty* - **Lamellar keratoplasty** (e.g., DSAEK, DMEK) is a common surgical treatment for bullous keratopathy, where diseased posterior corneal layers are replaced. - The goal is to replace the dysfunctional endothelium and restore corneal clarity and function. *Lenses can be prescribed for such patients* - **Contact lenses**, particularly bandage contact lenses, can be prescribed to patients with bullous keratopathy to protect the cornea and alleviate pain. - They act as a physical barrier against ruptured bullae, promoting epithelial healing and comfort. *Seen in Fuchs' dystrophy* - **Fuchs' endothelial dystrophy** is a common cause of bullous keratopathy, where there's a progressive loss of corneal endothelial cells. - This endothelial dysfunction leads to an accumulation of fluid within the cornea, causing edema and the formation of epithelial bullae.

Q: Quantification of corneal sensation is done by?

Aesthesiometer. ***Aesthesiometer*** - An **aesthesiometer** is a specialized device used to measure the **corneal sensation** or sensitivity, typically by applying a controlled stimulus to the corneal surface. - It helps in diagnosing conditions affecting **corneal nerves**, such as **diabetic neuropathy** or post-surgical nerve damage. *Pachymeter* - A **pachymeter** is an ultrasonic device used to measure the **central corneal thickness (CCT)**. - This measurement is crucial for **intraocular pressure (IOP)** interpretation and evaluating conditions like **corneal edema** or **Fuchs' endothelial dystrophy**. *Keratometer* - A **keratometer** is an ophthalmic instrument used to measure the **curvature of the anterior surface of the cornea**. - It is primarily used to assess **corneal astigmatism** and to fit **contact lenses**. *Tonometer* - A **tonometer** is an instrument used to measure **intraocular pressure (IOP)**, which is essential for diagnosing and managing **glaucoma**. - It does not quantify corneal sensation but rather the **fluid pressure within the eye**.

Q: Munson's sign is a feature of ?

Keratoconus. ***Keratoconus*** - **Munson's sign** is observed in advanced keratoconus, where the **conical protrusion of the cornea** indents the lower eyelid on downgaze. - This sign indicates significant **corneal thinning and steepening**. *Corneal ulcer* - A **corneal ulcer** is an open sore on the cornea, often caused by infection or trauma. - It presents with pain, redness, tearing, and photophobia, and does not cause **Munson's sign**. *Pterygium* - **Pterygium** is a triangular growth of conjunctival tissue that extends onto the cornea. - It is typically associated with UV exposure and does not cause corneal shape changes leading to **Munson's sign**. *Posterior staphyloma* - A **posterior staphyloma** is an outpouching of the posterior sclera, often seen in high myopia. - This condition affects the posterior segment of the eye and does not manifest with **Munson's sign**, which is an anterior corneal finding.

Q: What is the dye and filter used to diagnose corneal ulcers?

Fluorescein dye - visualized under cobalt blue filter. ***Fluorescein dye - visualized under cobalt blue filter*** - **Fluorescein dye** is applied to the eye, and it stains areas of **epithelial defects**, such as those found in corneal ulcers, appearing bright green. - The **cobalt blue filter** enhances the visibility and fluorescence of the stained areas, making corneal ulcers clearly discernible. *Lissamine green dye - visualized under green filter* - **Lissamine green** is used to identify **devitalized cells** and **mucous filaments** on the ocular surface, rather than primary corneal epithelial defects. - It is visualized under **white light or red-free filter**, not a green filter, and is less suitable for diagnosing corneal ulcers directly. *Lissamine blue dye - visualized under cobalt blue filter* - This option refers to a non-existent dye combination for routine corneal ulcer diagnosis. **Lissamine blue** is not a standard ophthalmic dye for this purpose. - While a cobalt blue filter is used with fluorescein, it is not paired with a "Lissamine blue dye." *Fluorescein dye - visualized under green filter* - **Fluorescein dye** is indeed the correct dye for diagnosing corneal ulcers by staining epithelial defects. - However, it is visualized under a **cobalt blue filter**, not a green filter, to maximize fluorescence and contrast.

Q: What is a characteristic finding in fungal corneal ulcers?

Satellite lesions. ***Satellite lesions*** - **Fungal corneal ulcers** often present with characteristic **satellite lesions**, which are smaller, adjacent infiltrates surrounding the main ulcer. - These lesions indicate the spread of fungal hyphae into the surrounding corneal stroma. - This is the **most characteristic feature** that helps distinguish fungal from bacterial keratitis. *Dendritic ulcer* - A **dendritic ulcer** is pathognomonic for **herpes simplex keratitis**, not fungal infections. - It presents as a branching, tree-like epithelial defect, which is distinct from the appearance of fungal ulcers. *Ring abscess* - A **ring abscess** is more commonly associated with **Acanthamoeba keratitis** or severe bacterial infections. - While it can occur in very advanced fungal infections, it is not a characteristic initial finding. *White hypopyon* - While fungal keratitis can present with a **white, fluffy hypopyon**, this is not specific enough to be the most characteristic finding. - Hypopyon indicates severe inflammation and can be seen in bacterial, fungal, and other severe corneal infections. - The presence of **satellite lesions** remains the key distinguishing feature for fungal etiology.

Q: Kayser-Fleischer rings (KF rings) are seen in:

Wilson's disease. ***Wilson's disease*** - **Kayser-Fleischer (KF) rings** are pathognomonic for **Wilson's disease**, resulting from **copper deposition** in the Descemet's membrane of the cornea. - This genetic disorder leads to excessive **copper accumulation** in the liver, brain, and other tissues due to impaired copper excretion. *Pterygium* - A **pterygium** is a benign growth of the **conjunctiva** that extends onto the cornea, typically appearing as a fleshy, triangular lesion. - It is not associated with systemic copper metabolism disorders or the presence of KF rings. *Hemochromatosis* - **Hemochromatosis** is a disorder of **iron overload**, leading to iron deposition in various organs, including the liver, heart, and pancreas. - It does not involve copper metabolism or the formation of corneal rings. *Menke's kinked hair syndrome* - **Menke's syndrome** is a genetic disorder characterized by **copper deficiency**, leading to impaired copper transport and utilization. - It presents with severe neurological deterioration, connective tissue abnormalities, and characteristic **kinky hair**, but not KF rings.

Q: All are true regarding cornea except:

The cornea is richly vascular.. ***The cornea is richly vascular.*** - The cornea is an **avascular** tissue, meaning it lacks blood vessels, which is crucial for its transparency. - This avascularity helps prevent light scatter and maintains clear vision. - The cornea receives nutrition from the **aqueous humor**, **tear film**, and **limbal blood vessels** through diffusion. *Endothelium help in maintaining dehydrated state* - The **corneal endothelium** actively pumps fluid out of the corneal stroma via **Na-K-ATPase pumps**, preventing swelling and maintaining its relative state of dehydration. - This **deturgescence** is essential for the cornea's transparency and optimal refractive power. *Oxygen is mostly derived by epithelium directly from the air through tear film* - The corneal **epithelium** primarily obtains oxygen directly from the atmosphere via the **tear film** when the eyes are open. - During sleep, oxygen is primarily supplied by the **palpebral conjunctival vessels**. *Corneal thickness is greater at periphery than center* - The cornea is **thinner at the center** (around 520-540 µm) and gradually **thicker towards the periphery** (around 600-640 µm). - This structural difference contributes to its optical properties and mechanical stability.

Q: Which organism can penetrate corneal endothelium?

Haemophilus influenzae. ***Haemophilus influenzae*** - *Haemophilus influenzae* is unique in its ability to penetrate the **intact corneal endothelium** through its specific virulence factors and enzymatic mechanisms. - Along with *Neisseria meningitidis*, it can breach the **Descemet's membrane and endothelial barrier** without requiring prior epithelial damage. - This property makes it particularly dangerous as it can cause **endophthalmitis** by directly accessing the anterior chamber. *Neisseria gonorrhoeae* - While highly virulent, *N. gonorrhoeae* penetrates the **corneal epithelium** (outer layer) through its proteases, not the endothelium (inner layer). - It causes severe **hyperacute conjunctivitis** and can lead to **corneal perforation**, but via epithelial destruction and stromal infiltration. *Staphylococcus aureus* - A common cause of **bacterial keratitis** following epithelial defects or trauma. - Causes stromal infiltration and abscess formation but **cannot penetrate intact endothelium**. *Aspergillus fumigatus* - This fungus causes **fungal keratitis** typically after trauma with vegetative matter. - Invades through **epithelial breaches** and stromal infiltration, not through intact endothelial penetration.

Question 1

Placido disc is used for diagnosing which of the following conditions?

Accepted Answer

Keratoconus

Answer

Uveitis

Answer

Retinoblastoma

Answer

Retinal detachment

Question 2

Topical antifungal of choice for Aspergillus infection of the eye?

Accepted Answer

Natamycin

Answer

Clotrimazole

Answer

Miconazole

Answer

Fluconazole

Question 3

All are true about Bullous keratopathy except which of the following?

Accepted Answer

Seen in Macular dystrophy

Answer

Lenses can be prescribed for such patients

Answer

Seen in Fuchs' dystrophy

Answer

Treatment is lamellar keratoplasty

Question 4

Quantification of corneal sensation is done by?

Accepted Answer

Aesthesiometer

Answer

Pachymeter

Answer

Keratometer

Answer

Tonometer

Question 5

Munson's sign is a feature of ?

Accepted Answer

Keratoconus

Answer

Corneal ulcer

Answer

Pterygium

Answer

Posterior staphyloma

Question 6

What is the dye and filter used to diagnose corneal ulcers?

Accepted Answer

Fluorescein dye - visualized under cobalt blue filter

Answer

Lissamine green dye - visualized under green filter

Answer

Lissamine blue dye - visualized under cobalt blue filter

Answer

Fluorescein dye - visualized under green filter

Question 7

What is a characteristic finding in fungal corneal ulcers?

Accepted Answer

Satellite lesions

Answer

Dendritic ulcer

Answer

Ring abscess

Answer

White hypopyon

Question 8

Kayser-Fleischer rings (KF rings) are seen in:

Accepted Answer

Wilson's disease

Answer

Pterygium

Answer

Hemochromatosis

Answer

Menke's kinked hair syndrome

Question 9

All are true regarding cornea except:

Accepted Answer

The cornea is richly vascular.

Answer

Endothelium help in maintaining dehydrated state

Answer

Oxygen is mostly derived by epithelium directly from the air through tear film

Answer

Corneal thickness is greater at periphery than center

Question 10

Which organism can penetrate corneal endothelium?

Accepted Answer

Haemophilus influenzae

Answer

Staphylococcus Aureus

Answer

Aspergillus fumigatus

Answer

Neisseria gonorrhoeae

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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