Diseases of the Cornea Practice Questions

Q: Corneal diameter is increased in which of the following conditions?

All of the above. **Explanation:** The correct answer is **D. All of the above**, as each of these conditions involves an increase in the horizontal or overall corneal diameter, though the underlying mechanisms differ. 1. **Megalocornea:** This is a non-progressive, bilateral, X-linked recessive condition where the horizontal corneal diameter is **>13 mm** at birth or in adulthood. Importantly, the intraocular pressure (IOP) and corneal thickness are usually normal, distinguishing it from congenital glaucoma (buphthalmos). 2. **Keratoglobus:** This is a rare, non-inflammatory corneal ectasia where the entire cornea becomes extremely thin (especially at the periphery) and bulges forward in a **globular shape**. This protrusion leads to a significant increase in the measured corneal diameter and surface area. 3. **Keratoconus:** While primarily characterized by localized paracentral thinning and cone-shaped protrusion, advanced cases of keratoconus involve significant stretching of the corneal tissue. This ectasia results in an increased chord length and overall diameter of the cornea. **Clinical Pearls for NEET-PG:** * **Buphthalmos vs. Megalocornea:** In Buphthalmos (congenital glaucoma), the cornea is large (>12 mm before age 1) but is associated with **Haab’s striae** (tears in Descemet’s membrane) and raised IOP. Megalocornea has a clear cornea and normal IOP. * **Microcornea:** Defined as a diameter **<10 mm** at any age or **<9 mm** in a newborn. It is often associated with Nanophthalmos. * **Keratoglobus Risk:** Patients are at high risk of corneal perforation even with minor trauma due to extreme peripheral thinning. * **Normal Diameter:** The average adult horizontal corneal diameter is **11.7 mm**.

Q: Vortex keratopathy is seen with all the following drugs except:

Thioxanthines. **Explanation:** **Vortex Keratopathy (Cornea Verticillata)** is characterized by fine, golden-brown or greyish-white whorl-like opacities in the corneal epithelium. It occurs due to the deposition of drugs or their metabolites within the lysosomes of corneal epithelial cells (a form of drug-induced lipidosis). **Why Thioxanthines is the correct answer:** Thioxanthines (antipsychotics like Thiothixene) are primarily associated with **pigmentary deposits on the corneal endothelium and anterior lens capsule**, rather than the epithelial whorl patterns seen in vortex keratopathy. Therefore, it is the "except" in this list. **Analysis of Incorrect Options:** * **Phenothiazines:** Specifically **Chlorpromazine**, can cause vortex keratopathy, although it is more classically known for causing "star-shaped" anterior subcapsular cataracts and endothelial deposits. * **Tamoxifen:** This selective estrogen receptor modulator (SERM) used in breast cancer is a well-known cause of vortex keratopathy and crystalline retinopathy. * **Indomethacin:** This NSAID is a classic cause of whorl-like corneal deposits, which are usually dose-dependent and reversible upon discontinuation. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Vortex Keratopathy (CHAI-T):** **C**hloroquine/Hydroxychloroquine, **H**eamiodarone (Amiodarone - most common cause), **A**tovaquone, **I**ndomethacin, and **T**amoxifen. * **Fabry Disease:** The most important systemic (non-drug) cause of vortex keratopathy. If seen in a patient not on these medications, suspect an alpha-galactosidase A deficiency. * **Visual Impact:** Vortex keratopathy is usually asymptomatic and rarely affects visual acuity, thus drug discontinuation is seldom required unless systemic toxicity is suspected.

Q: Cornea verticillata is caused by which of the following medications?

Amiodarone. **Explanation:** **Cornea verticillata** (also known as vortex keratopathy) is characterized by fine, bilateral, golden-brown or greyish deposits in the corneal epithelium, typically arranged in a whorl-like pattern. **Why Amiodarone is correct:** Amiodarone is a Class III anti-arrhythmic drug known to cause lipidosis in the corneal epithelium. It binds to polar lipids, making them indigestible by lysosomal enzymes, leading to their accumulation. Nearly all patients on long-term amiodarone therapy develop these deposits. While they are usually asymptomatic and do not require discontinuation of the drug, they can occasionally cause visual halos or blurred vision. **Why other options are incorrect:** * **Erythromycin:** This is a macrolide antibiotic used topically for neonatal prophylaxis or bacterial conjunctivitis; it does not cause corneal deposits. * **Timolol:** A non-selective beta-blocker used to treat glaucoma. Its primary ocular side effects include stinging, dry eyes, and bradycardia, but not vortex keratopathy. * **Tetracycline:** While systemic tetracyclines can cause skin or tooth discoloration and are associated with pseudotumor cerebri, they do not cause the specific whorl-like corneal deposits seen in cornea verticillata. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Cornea Verticillata (CHAI-T):** **C**hloroquine/Hydroxychloroquine, **H**eavy metals (Gold, Iron), **A**miodarone, **I**ndomethacin, and **T**amoxifen. * **Fabry Disease:** This is the most important systemic condition associated with cornea verticillata (due to glycosphingolipid accumulation). * **Reversibility:** Amiodarone-induced deposits are typically reversible upon cessation of the drug, though this is rarely necessary.

Q: Which of the following types of corneal degeneration is most commonly seen in patients with trachoma?

Salzmann's nodular degeneration. **Explanation:** **Salzmann’s Nodular Degeneration (SND)** is the correct answer because it is a non-inflammatory condition characterized by the formation of bluish-white or greyish subepithelial nodules. It typically occurs as a late sequela to **chronic keratitis** or long-standing ocular surface inflammation. **Trachoma** is a leading cause of chronic keratoconjunctivitis, and the resulting chronic irritation and scarring predispose the cornea to these nodular deposits (composed of hyaline and collagen). **Analysis of Incorrect Options:** * **A. Terrien’s Disease:** This is a peripheral corneal thinning (marginal degeneration) characterized by vascularization, lipid deposition, and "gutter" formation. It is idiopathic and not typically associated with trachoma. * **B. Band Keratopathy:** This involves the deposition of calcium salts in the Bowman’s membrane. It is most commonly associated with chronic uveitis (especially in Juvenile Idiopathic Arthritis), hypercalcemia, or long-term silicone oil in the eye. * **C. Labrador Keratopathy (Spheroidal Degeneration):** Also known as Climatic Droplet Keratopathy, it is caused by chronic exposure to **UV radiation**, wind, and sand. It presents as amber-colored granules in the superficial stroma. **High-Yield Clinical Pearls for NEET-PG:** * **SND Appearance:** Nodules are often arranged in a circular fashion around the pupillary area or at the edge of old corneal scars. * **SND Management:** Usually asymptomatic; however, if vision is affected or irritation occurs, treatment involves superficial keratectomy or PTK (Phototherapeutic Keratectomy). * **Trachoma Association:** Remember the "SAFE" strategy for Trachoma (Surgery, Antibiotics, Facial cleanliness, Environmental improvement). SND is a late degenerative change, unlike the acute inflammatory signs like Herbert’s pits or Arlt’s line.

Q: Which corneal layer is responsible for deturgescence?

Endothelium. **Explanation:** The **corneal endothelium** is a single layer of hexagonal cells that plays a critical role in maintaining **corneal deturgescence**—the state of relative dehydration (approx. 78% water content) required for corneal transparency. It achieves this through two mechanisms: 1. **Active Endothelial Pump:** Na⁺/K⁺-ATPase pumps actively transport ions from the stroma into the aqueous humor, creating an osmotic gradient that draws water out. 2. **Leaky Barrier:** While it acts as a physical barrier, it allows controlled leakage of nutrients from the aqueous into the stroma. **Analysis of Incorrect Options:** * **Bowman’s Membrane (A):** An acellular, condensed layer of collagen. It provides structural integrity but has no metabolic or pumping function. It does not regenerate if damaged. * **Epithelium (C):** While the epithelium acts as a highly effective physical barrier to water (preventing tears from entering the stroma), it lacks the active metabolic "pump" capacity of the endothelium. * **Stroma (D):** The thickest layer (90%), composed of regularly arranged collagen fibrils. It is naturally hydrophilic (due to GAGs) and tends to swell; it is the *beneficiary* of deturgescence, not the cause. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Cell Count:** Normal endothelial cell count is 2500–3000 cells/mm². If the count falls below **500 cells/mm²**, the pump fails, leading to corneal edema (Bullous Keratopathy). * **Regeneration:** Endothelial cells **do not regenerate** in vivo; they heal by enlargement and migration (pleomorphism and polymegethism). * **Specular Microscopy:** The gold standard investigation to assess endothelial cell density and morphology.

Q: Klebsiella pneumoniae is a common cause of which of the following ocular conditions?

Keratitis. **Explanation:** **Correct Answer: C. Keratitis** *Klebsiella pneumoniae* is a Gram-negative, encapsulated, opportunistic pathogen. In ophthalmology, it is a significant cause of **bacterial keratitis** (corneal ulcers), particularly in patients with pre-existing ocular surface diseases, diabetes mellitus, or those who are immunocompromised. While *Staphylococcus aureus* and *Pseudomonas aeruginosa* are more common overall, *Klebsiella* is noted for causing aggressive corneal suppuration and dense stromal infiltration. **Why other options are incorrect:** * **A. Chalazion:** This is a chronic, non-infectious granulomatous inflammation of the **Meibomian glands** caused by retained secretions (sebum), not an acute bacterial infection. * **B. Entropion:** This is an anatomical malposition where the eyelid margin rolls inward. It is caused by involutional changes, scarring (cicatricial), or muscle spasms, rather than a primary infection by *Klebsiella*. * **D. Stye (Hordeolum):** An acute focal pyogenic infection of the eyelid glands (Zeis/Moll for external; Meibomian for internal). The most common causative organism is almost exclusively ***Staphylococcus aureus***. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of Bacterial Keratitis:** *Staphylococcus aureus* (overall) and *Pseudomonas* (specifically in contact lens wearers). * **Hypopyon Ulcer:** Classically associated with *Pneumococcus* (ulcus serpens) and *Fungal keratitis*. * **Klebsiella specific:** Often associated with "sticky" or mucoid discharge due to its prominent polysaccharide capsule. * **Treatment:** Bacterial keratitis is treated with fortified antibiotics (e.g., Cephazolin + Tobramycin) or fluoroquinolones (e.g., Moxifloxacin).

Q: Interstitial keratitis is caused by all of the following except?

Pertussis. **Explanation:** Interstitial Keratitis (IK) is a chronic non-ulcerative inflammation of the corneal stroma, characterized by cellular infiltration and vascularization without involvement of the epithelium or endothelium. It is primarily an **immune-mediated (Type IV hypersensitivity)** response to a persistent antigen rather than a direct active infection of the cornea. **Why Pertussis is the correct answer:** Pertussis (Whooping Cough), caused by *Bordetella pertussis*, is a respiratory infection that does not have any known association with corneal pathology or the immune-mediated triggers required to cause interstitial keratitis. **Analysis of other options:** * **Tuberculosis (TB):** Historically the second most common cause of IK. It typically presents as a unilateral sectoral inflammation of the stroma. * **Herpes Simplex Virus (HSV):** A very common cause of "viral IK." It occurs as an immune response to viral antigens residing in the stroma, often following previous dendritic keratitis. * **Epstein-Barr Virus (EBV):** A known viral trigger for IK, often presenting with multifocal, discrete stromal opacities (nummular keratitis). **High-Yield Clinical Pearls for NEET-PG:** * **Most Common Cause:** Globally, **Syphilis** (Congenital > Acquired) is the most common cause of IK. * **Hutchinson’s Triad (Congenital Syphilis):** Interstitial keratitis, Hutchinson’s teeth (notched incisors), and Sensorineural deafness (8th nerve palsy). * **Cogan’s Syndrome:** A rare non-syphilitic cause featuring IK, vestibulo-auditory symptoms (vertigo/tinnitus), and systemic vasculitis. * **Clinical Sign:** "Salmon patch" appearance (active neovascularization) and "Ghost vessels" (regressed vessels after healing).

Question 1

Corneal diameter is increased in which of the following conditions?

Accepted Answer

All of the above

Answer

Megalocornea

Answer

Keratoglobus

Answer

Keratoconus

Question 2

Corneal transplantation requires which of the following procedures?

Accepted Answer

Specular microscopy is performed for corneal endothelial cell count.

Answer

Donor older than 60 years is not allowed.

Answer

The whole eye is preserved in culture.

Answer

HLA matching is a requirement.

Question 3

Vortex keratopathy is seen with all the following drugs except:

Accepted Answer

Thioxanthines

Answer

Phenothiazines

Answer

Tamoxifen

Answer

Indomethacin

Question 4

Cornea verticillata is caused by which of the following medications?

Accepted Answer

Amiodarone

Answer

Erythromycin

Answer

Timolol

Answer

Tetracycline

Question 5

Which of the following types of corneal degeneration is most commonly seen in patients with trachoma?

Accepted Answer

Salzmann's nodular degeneration

Answer

Terrien's disease

Answer

Band keratopathy

Answer

Labrador keratopathy

Question 6

Which corneal layer is responsible for deturgescence?

Accepted Answer

Endothelium

Answer

Bowman's membrane

Answer

Epithelium

Answer

Stroma

Question 7

Corneal ulceration may be caused by injury to which cranial nerve?

Accepted Answer

Fifth

Answer

Third

Answer

Sixth

Answer

All of the above

Question 8

Which of the following is NOT true for Mooren's ulcer?

Accepted Answer

Perforation of the cornea is a common complication.

Answer

It can be a type of peripheral ulcerative keratitis.

Answer

The advancing edge of the ulcer is typically undermined.

Answer

The floor of the ulcer is quickly vascularized.

Question 9

Klebsiella pneumoniae is a common cause of which of the following ocular conditions?

Accepted Answer

Keratitis

Answer

Chalazion

Answer

Entropion

Answer

Stye

Question 10

Interstitial keratitis is caused by all of the following except?

Accepted Answer

Pertussis

Answer

Tuberculosis (TB)

Answer

Herpes Simplex Virus (HSV)

Answer

Epstein-Barr Virus (EBV)

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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