Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 61: In a child with juvenile rheumatoid arthritis, what is a common finding on eye examination?

A. Band keratopathy (Correct Answer)
B. Vortex keratopathy
C. Fuchs endothelial dystrophy
D. Bitot spots

Explanation: **Explanation:** **Juvenile Idiopathic Arthritis (JIA)**, particularly the oligoarticular subtype, is strongly associated with **Chronic Nonspecific Anterior Uveitis**. This inflammation is often asymptomatic ("white eye") but can lead to significant complications. **Band Keratopathy** is a classic finding in these patients, characterized by the horizontal deposition of calcium salts (hydroxyapatite) in the subepithelial layers, Bowman’s membrane, and anterior stroma of the cornea. It typically starts at the periphery (3 and 9 o'clock positions) and progresses centrally, often showing a "Swiss cheese" appearance due to holes where corneal nerves penetrate. **Analysis of Incorrect Options:** * **Vortex Keratopathy (Cornea Verticillata):** Characterized by whorl-like epithelial deposits. It is associated with **Amiodarone** use or **Fabry disease**, not inflammatory arthritis. * **Fuchs Endothelial Dystrophy:** A bilateral, slowly progressive genetic disorder of the corneal endothelium leading to stromal edema. It typically presents in elderly patients, not children. * **Bitot Spots:** These are foamy, triangular patches on the conjunctiva caused by **Vitamin A deficiency** and squamous metaplasia. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of JIA-associated Uveitis:** Iridocyclitis, Band Keratopathy, and Complicated Cataract. * **Risk Factor:** Children who are **ANA (Antinuclear Antibody) positive** are at the highest risk for developing uveitis and require frequent slit-lamp screening. * **Treatment of Band Keratopathy:** If vision is affected, the treatment of choice is **chelation** using **EDTA (Ethylenediaminetetraacetic acid)**.

Question 62: Brown skin cornea is seen in?

A. Siderosis (Correct Answer)
B. Mustard gas exposure
C. Chalcosis
D. Argyrosis

Explanation: **Explanation:** The term **"Brown skin cornea"** refers to the characteristic rusty-brown discoloration of the corneal stroma and epithelium seen in **Siderosis bulbi**. This condition occurs due to the intraocular retention of an iron-containing foreign body. The iron undergoes oxidation, and the resulting ferric ions are deposited in the epithelial cells of various ocular structures (cornea, lens, and retina), leading to toxic degenerative changes. **Analysis of Options:** * **A. Siderosis (Correct):** Iron deposition leads to a classic rusty-brown discoloration of the cornea. Other features include "Rusty" cataract (subcapsular deposits) and pigmentary retinopathy. * **B. Mustard Gas Exposure:** This typically causes a "delayed keratitis" characterized by corneal scarring, vascularization, and a "marbled" appearance of the conjunctiva, but not a brown skin cornea. * **C. Chalcosis:** This is caused by intraocular **copper** foreign bodies. It leads to a **"Sunflower cataract"** and a **Kayser-Fleischer (KF) ring** (golden-brown/greenish deposit in the Descemet’s membrane), but the overall corneal stroma does not take on a "brown skin" appearance. * **D. Argyrosis:** This results from chronic **silver** deposition. It typically causes a permanent **slate-grey or bluish-black** discoloration of the conjunctiva and Descemet’s membrane. **High-Yield Clinical Pearls for NEET-PG:** * **Siderosis:** Look for "Rusty" deposits and ERG changes (initially increased a-wave, later extinguished). * **Chalcosis:** Associated with copper; remember the "Sunflower cataract." * **Kayser-Fleischer Ring:** Seen in Wilson’s Disease (Copper deposition in Descemet's membrane). * **Hudson-Stahli Line:** Iron deposition in the corneal epithelium (normal aging or chronic tear film instability). * **Flecked Retina:** Often associated with Alport syndrome or Fundus Albipunctatus.

Question 63: What is keratometry used for?

A. Measuring curvature of the anterior surface of the cornea (Correct Answer)
B. Calculating axial length of the eyeball
C. Endothelial cell count
D. Intraocular pressure

Explanation: **Explanation:** **1. Why Option A is Correct:** Keratometry is the measurement of the **curvature of the anterior surface of the cornea**. It works on the principle that the anterior corneal surface acts as a convex mirror. By measuring the size of the reflected image (Purkinje image I) of an object of known size, the radius of curvature ($r$) can be calculated. This is then converted into dioptric power using the keratometric refractive index (usually 1.3375). It specifically measures the central 3 mm of the cornea. **2. Why Other Options are Incorrect:** * **Option B (Axial Length):** This is measured using **A-scan Ultrasonography**. While both keratometry and axial length are required for IOL power calculation (using formulas like SRK), keratometry itself does not measure length. * **Option C (Endothelial Cell Count):** This is performed using **Specular Microscopy**. It evaluates the health, density, and morphology (pleomorphism/polymegethism) of the corneal endothelium. * **Option D (Intraocular Pressure):** This is measured via **Tonometry** (e.g., Goldmann Applanation Tonometry, Schiotz tonometry). **3. High-Yield Clinical Pearls for NEET-PG:** * **IOL Power Calculation:** The most common clinical use of keratometry is calculating the power of an Intraocular Lens (IOL) before cataract surgery. * **Astigmatism:** Keratometry helps identify the type of astigmatism (With-the-rule vs. Against-the-rule) by comparing the refractive power in different meridians. * **Contact Lens Fitting:** Essential for determining the base curve of a contact lens. * **Keratoconus:** Early screening often shows irregular mires or steepening of the corneal curvature on keratometry. * **Topography vs. Keratometry:** While keratometry measures only the central 3mm, **Corneal Topography** provides a detailed map of the entire corneal surface.

Question 64: Corneal dystrophies are usually:

A. Primarily unilateral
B. Primarily bilateral (Correct Answer)
C. Primarily unilateral without systemic disease
D. Primarily bilateral with systemic disease

Explanation: **Explanation:** Corneal dystrophies are a group of genetically determined, progressive, and non-inflammatory disorders that affect specific layers of the cornea. **1. Why Option B is Correct:** The hallmark of corneal dystrophies is that they are **primarily bilateral and symmetrical**. Because these conditions are inherited (most commonly as autosomal dominant traits), the genetic defect is present in both eyes from birth. Although they may not manifest clinically until the first or second decade of life, they typically progress slowly and involve both eyes equally. **2. Why Other Options are Incorrect:** * **Options A & C:** Corneal **degenerations** (like Terrien’s marginal degeneration) or infections are often unilateral or asymmetric. Dystrophies, by definition, are bilateral. * **Option D:** Corneal dystrophies are characteristically **isolated to the eye** and are **not** associated with systemic diseases. If a corneal deposit is associated with a systemic condition (e.g., Kayser-Fleischer rings in Wilson’s disease), it is classified as a corneal manifestation of a systemic disease, not a primary dystrophy. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** Most are Autosomal Dominant (AD), except **Macular Corneal Dystrophy**, which is **Autosomal Recessive (AR)** and is the most severe. * **Layer-wise Classification:** * *Epithelial:* Meesmann dystrophy. * *Stromal:* Granular, Lattice, and Macular (Mnemonic: **M**any **L**ittle **G**eese = **M**acular, **L**attice, **G**ranular). * *Endothelial:* Fuchs’ endothelial dystrophy (presents with "beaten metal" appearance/corneal guttata). * **Staining Mnemonics:** **M**acular = **A**lcian Blue; **L**attice = **C**ongo Red (Amyloid); **G**ranular = **M**asson Trichrome (Hyaline). (Mnemonic: **M**arilyn **M**onroe **A**lways **G**ets **H**er **M**en in **L**A **C**ity).

Question 65: Corneal ulceration may be caused by injury to which cranial nerve?

A. Third
B. Fifth (Correct Answer)
C. Sixth
D. All of the above

Explanation: **Explanation:** The correct answer is the **Fifth Cranial Nerve (Trigeminal Nerve)**, specifically its ophthalmic division ($V_1$). **Why the Fifth Nerve is Correct:** The trigeminal nerve provides sensory innervation to the cornea via the long ciliary nerves. This sensory pathway is vital for two reasons: 1. **The Corneal Reflex:** Sensory input from the cornea triggers the motor limb (Facial nerve) to blink, protecting the eye from foreign bodies. 2. **Trophic Function:** The nerve releases neuropeptides (like Substance P) that maintain the health, metabolism, and regeneration of the corneal epithelium. Damage to the Fifth nerve leads to **Neurotrophic Keratopathy**. The resulting anesthesia means the patient does not feel trauma or dryness, leading to epithelial breakdown, persistent defects, and eventually, a **Neurotrophic Ulcer**. **Why Other Options are Incorrect:** * **Third (Oculomotor) Nerve:** Damage causes ptosis (drooping of the eyelid). While this affects eye movement and pupil size, it actually *protects* the cornea from exposure by keeping the lid closed. * **Sixth (Abducens) Nerve:** Damage causes lateral rectus palsy and diplopia (double vision) but does not affect corneal sensation or lid closure; therefore, it does not cause ulceration. * **Note on the Seventh (Facial) Nerve:** While not an option here, damage to the 7th nerve causes **Exposure Keratopathy** due to the inability to close the eye (lagophthalmos), which is another common cause of neurogenic ulceration. **High-Yield Clinical Pearls for NEET-PG:** * **Neurotrophic Ulcer Characteristics:** Typically presents as a "punched-out" ulcer with smooth, rolled-in edges and a lack of pain (anesthesia). * **Common Causes of 5th Nerve Damage:** Herpes Simplex/Zoster Keratitis (most common), acoustic neuroma, or diabetes. * **Treatment Tip:** Avoid toxic preservatives; use lubricants, bandage contact lenses, or **tarsorrhaphy** (suturing eyelids) to protect the surface.

Question 66: Which of the following is NOT true for Mooren's ulcer?

A. It can be a type of peripheral ulcerative keratitis.
B. The advancing edge of the ulcer is typically undermined.
C. Perforation of the cornea is a common complication. (Correct Answer)
D. The floor of the ulcer is quickly vascularized.

Explanation: ### Explanation: Mooren’s Ulcer Mooren’s ulcer is a rare, idiopathic, chronic, and progressive **peripheral ulcerative keratitis (PUK)** characterized by an autoimmune-mediated destruction of the corneal stroma. **Why Option C is the Correct Answer (The False Statement):** While Mooren’s ulcer is a destructive process, **perforation is actually uncommon**. This is because the inflammatory process primarily involves the superficial to mid-stroma, and the underlying Descemet’s membrane usually remains intact. Even in severe cases, the ulcer tends to spread circumferentially and centripetally rather than deeply into the globe. **Analysis of Incorrect Options:** * **Option A:** Mooren’s ulcer is a classic example of **idiopathic PUK**. It is a diagnosis of exclusion, meaning it occurs in the absence of any systemic collagen vascular disease (like Rheumatoid Arthritis). * **Option B:** A pathognomonic feature of Mooren’s ulcer is its **undermined, overhanging leading edge**. The ulceration "digs" into the stroma, leaving the superficial epithelium overhanging the active site. * **Option D:** As the ulcer progresses, the base (floor) undergoes healing characterized by **rapid vascularization** and thinning, which eventually leads to a scarred, opacified peripheral cornea. --- ### High-Yield Clinical Pearls for NEET-PG: 1. **Two Clinical Types:** * **Type 1 (Benign):** Unilateral, occurs in elderly patients, responds well to treatment. * **Type 2 (Malignant):** Bilateral, occurs in younger patients (often of African descent), rapidly progressive, and highly resistant to therapy. 2. **Key Histopathology:** It is a **Type II and Type IV hypersensitivity** reaction. 3. **Management:** Topical steroids are the first line, but systemic immunosuppressants (like Cyclosporine or Azathioprine) and surgical interventions (conjunctival resection/peritomy) are often required for Type 2. 4. **Differentiating Feature:** Unlike other PUKs, Mooren’s ulcer **never involves the sclera** (it is strictly limited to the cornea).

Question 67: Klebsiella pneumoniae is a common cause of which of the following ocular conditions?

A. Chalazion
B. Entropion
C. Keratitis (Correct Answer)
D. Stye

Explanation: **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).

Question 68: Which corneal layer does not regenerate?

A. Bowman's layer (Correct Answer)
B. Stroma
C. Descemet's membrane
D. Epithelium

Explanation: **Explanation:** The cornea consists of five primary layers (from anterior to posterior): Epithelium, Bowman’s layer, Stroma, Descemet’s membrane, and Endothelium. The ability of these layers to regenerate depends on their cellular composition and embryonic origin. **Why Bowman’s Layer is the Correct Answer:** Bowman’s layer is an acellular, condensed layer of collagen fibers located between the epithelial basement membrane and the stroma. Because it lacks regenerative cells, any injury or damage to this layer results in permanent scarring (opacification). It does not "regrow"; instead, it is replaced by fibrous stromal tissue. **Analysis of Incorrect Options:** * **Epithelium:** This is the outermost layer and is highly regenerative. It is constantly renewed by limbal stem cells. Small abrasions usually heal within 24–48 hours without leaving a scar. * **Stroma:** While the stroma heals via fibrosis (which can lead to scarring), it does possess **keratocytes** (specialized fibroblasts) that can synthesize new collagen and extracellular matrix to repair the defect. * **Descemet’s Membrane:** This is the basement membrane of the endothelium. It is a true membrane that is secreted throughout life by the underlying endothelial cells; therefore, it has the capacity to regenerate. **High-Yield Clinical Pearls for NEET-PG:** * **Dua’s Layer:** A sixth layer (predominantly collagenous) discovered between the stroma and Descemet’s membrane. * **Endothelium:** Like Bowman’s layer, the **Endothelium does not regenerate** in humans. Instead, it heals by the enlargement and migration of existing cells (pleomorphism and polymegethism). If the endothelium was an option, it would also be a correct answer. * **Scarring Rule:** Any corneal injury involving Bowman’s layer or deeper will result in a permanent corneal opacity.

Question 69: Interstitial keratitis is caused by all of the following except?

A. Tuberculosis (TB)
B. Herpes Simplex Virus (HSV)
C. Epstein-Barr Virus (EBV)
D. Pertussis (Correct Answer)

Explanation: **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 70: Thinning of the cornea occurs in which condition?

A. Megalocornea
B. Bullous keratopathy
C. Endothelial dystrophy
D. Keratoconus (Correct Answer)

Explanation: **Explanation:** **Keratoconus** is a non-inflammatory, progressive ectatic disorder characterized by **central or paracentral thinning** of the corneal stroma. This thinning, combined with the eye's internal pressure, causes the cornea to bulge forward into a conical shape, leading to irregular astigmatism and visual impairment. **Analysis of Options:** * **Megalocornea (Option A):** This is a congenital anomaly where the corneal diameter is enlarged (>13 mm), but the **thickness is typically normal**. It is a static condition, not a thinning disorder. * **Bullous Keratopathy (Option B):** This occurs due to endothelial failure (often post-cataract surgery). The lack of a functional pump leads to stromal edema and epithelial blisters (bullae). Therefore, the cornea becomes **thickened (edematous)**, not thinned. * **Endothelial Dystrophy (Option C):** Conditions like Fuchs’ dystrophy involve the loss of endothelial cells. Similar to bullous keratopathy, this leads to corneal hydration and **increased thickness**. * **Keratoconus (Option D):** As the hallmark of ectatic diseases, it involves enzymatic degradation of the stromal matrix, leading to progressive **stromal thinning**. **High-Yield Clinical Pearls for NEET-PG:** * **Munson’s Sign:** V-shaped indentation of the lower lid on down-gazes. * **Vogt’s Striae:** Vertical stress lines in the deep stroma (disappear with external pressure). * **Fleischer’s Ring:** Iron deposition at the base of the cone (best seen with Cobalt blue filter). * **Rizutti’s Sign:** Conical reflection on the nasal cornea when light is shone from the temporal side. * **Management:** Collagen Cross-linking (CXL/C3R) to arrest progression; Penetrating Keratoplasty for advanced cases.

Practice by Chapter

Corneal Anatomy and Physiology

Practice Questions

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

Practice Questions

Corneal Dystrophies

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Keratoconus and Ectatic Disorders

Practice Questions

Corneal Transplantation

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Corneal Topography and Imaging

Practice Questions

Dry Eye Disease

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Corneal Trauma

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