Diseases of the Cornea — MCQs

Diseases of the Cornea Indian Medical PG Practice Questions and MCQs

Question 251: Fleischer ring is characteristic of which condition?

A. Megalocornea
B. Diabetes
C. Chalcosis
D. Keratoconus (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Keratoconus** **Mechanism:** The **Fleischer ring** is a classic clinical sign of **Keratoconus**, a non-inflammatory, progressive thinning and cone-like protrusion of the cornea. It is caused by the deposition of **hemosiderin (iron)** in the basal layers of the corneal epithelium. This iron typically accumulates at the base of the "cone" due to the pooling of tears in the area where the corneal curvature changes abruptly. It is best visualized using a **cobalt blue filter** under a slit-lamp examination. **Analysis of Incorrect Options:** * **A. Megalocornea:** This is a congenital anomaly where the corneal diameter is >13 mm. It is not associated with iron deposition rings. * **B. Diabetes:** While diabetes can cause corneal epitheliopathy or decreased sensitivity, it does not produce a Fleischer ring. (Note: Do not confuse this with the *Kayser-Fleischer ring* seen in Wilson’s disease). * **C. Chalcosis:** This refers to the deposition of **copper** in intraocular tissues (usually from a retained foreign body). It typically results in a "Sunflower cataract," not a Fleischer ring. **High-Yield Clinical Pearls for Keratoconus:** * **Munson’s Sign:** V-shaped indentation of the lower eyelid on downward gaze. * **Vogt’s Striae:** Vertical stress lines in the deep stroma/Descemet’s membrane. * **Rizutti’s Sign:** Conical reflection on the nasal cornea when light is shown from the temporal side. * **Hydrops:** Acute corneal edema due to a rupture in **Descemet’s membrane**. * **Management:** Early stages use RGP (Rigid Gas Permeable) lenses; progressive cases require **CXL (Collagen Cross-linking)**; advanced cases require Keratoplasty.

Question 252: Corneal sensation is diminished in which of the following conditions?

A. Band Keratopathy
B. Exposure Keratitis
C. Phlyctenular Keratitis
D. Dendritic Keratitis (Correct Answer)

Explanation: **Explanation:** **Dendritic Keratitis (Option D)** is the hallmark clinical presentation of **Herpes Simplex Virus (HSV)** keratitis. The virus infects the corneal epithelium and travels via the sensory nerve endings to the trigeminal ganglion. This process leads to significant **neurotrophic changes** and destruction of the subepithelial nerve plexus, resulting in **diminished or absent corneal sensation (hypesthesia)**. Testing for corneal sensation is a vital clinical step in differentiating HSV from other forms of keratitis. **Analysis of Incorrect Options:** * **Band Keratopathy (Option A):** This is a degenerative condition characterized by the deposition of calcium salts in the Bowman’s membrane. While it affects vision and causes irritation, it does not typically involve the nerve plexus to the point of anesthesia. * **Exposure Keratitis (Option B):** This occurs due to incomplete lid closure (e.g., Bell’s palsy). While the cornea becomes dry and ulcerated, the underlying nerve function remains intact initially; in fact, these patients often experience significant pain due to exposed nerve endings. * **Phlyctenular Keratitis (Option C):** This is a type IV hypersensitivity reaction to endogenous bacterial antigens (like Tubercular protein). It is characterized by intense photophobia and pain, with preserved corneal sensation. **High-Yield Clinical Pearls for NEET-PG:** * **Causes of Diminished Corneal Sensation:** Remember the mnemonic **"H-N-D"**: **H**erpes (Simplex and Zoster), **N**eurotrophic keratopathy (DM, Leprosy), and **D**rugs (Chronic use of topical anesthetics or Beta-blockers like Timolol). * **Acanthamoeba Keratitis:** Often presents with pain out of proportion to clinical signs, but can also lead to decreased sensation in later stages due to radial keratoneuritis. * **Absolute Contraindication:** Never use topical steroids in active Dendritic Keratitis as it can lead to a "Geographic Ulcer."

Question 253: All of the following are true about the layers of the cornea except?

A. Pre-Descemet's layer is also known as Dua's layer.
B. Type 2 and type 4 collagen are present in Descemet's membrane. (Correct Answer)
C. Corneal stroma is the thickest layer of the cornea.
D. The endothelium is responsible for maintaining the relatively dehydrated state of the cornea.

Explanation: The cornea consists of six distinct layers: Epithelium, Bowman’s layer, Stroma, Dua’s layer, Descemet’s membrane, and Endothelium. **Explanation of the Correct Answer (Option B):** This statement is incorrect because **Descemet’s membrane** (the basement membrane of the endothelium) is primarily composed of **Type IV collagen**. It does not contain Type II collagen. Type II collagen is typically found in the vitreous humor and cartilage, not the cornea. **Analysis of Other Options:** * **Option A:** **Dua’s Layer** (Pre-Descemet's layer) is the most recently discovered layer (2013). It is a thin, tough, acellular layer located between the stroma and Descemet’s membrane. * **Option C:** The **Corneal Stroma** (Substantia propria) accounts for approximately **90%** of the total corneal thickness. It is composed mainly of Type I collagen fibers arranged in a precise lattice pattern. * **Option D:** The **Endothelium** contains active **Na+/K+ ATPase pumps**. These pumps constantly move ions out of the stroma, drawing water with them to maintain "corneal deturgescence" (a state of relative dehydration), which is essential for transparency. **High-Yield Clinical Pearls for NEET-PG:** * **Regeneration:** The Epithelium and Descemet’s membrane can regenerate; **Bowman’s layer cannot** (damage results in scarring). * **Collagen Types:** Stroma = Type I; Descemet’s = Type IV. * **Dua’s Layer:** Important in lamellar corneal surgery (DALK) and provides structural integrity to the posterior cornea. * **Endothelial Cell Count:** Normal is 2500–3000 cells/mm². If it falls below 500 cells/mm², corneal edema occurs (Bullous Keratopathy).

Question 254: Chrysiaris is the deposition of which substance?

A. Silver in stroma of cornea
B. Gold in stroma of cornea (Correct Answer)
C. Iron in basement membrane
D. Copper in Descemet's membrane

Explanation: **Explanation:** **Chrysiaris** (also known as ocular chrysiasis) refers to the deposition of **gold salts** in the ocular tissues, most notably within the **stroma of the cornea**. This condition typically occurs as a side effect of long-term systemic gold therapy (chrysotherapy), which was historically used to treat rheumatoid arthritis. The deposits appear as fine, yellowish-brown or purple-to-violet granules, usually starting in the deep stroma and progressing superficially. **Analysis of Options:** * **Option A (Silver):** The deposition of silver in the cornea or conjunctiva is called **Argyrosis**. It typically presents as a slate-grey discoloration. * **Option C (Iron):** Iron deposition in the corneal epithelium/basement membrane is associated with several clinical signs, such as **Hudson-Stahli lines** (age-related), **Fleischer rings** (keratoconus), or **Ferry’s lines** (filtering blebs). * **Option D (Copper):** Copper deposition in the **Descemet’s membrane** is known as the **Kayser-Fleischer (KF) ring**, a hallmark of Wilson’s disease (hepatolenticular degeneration). **High-Yield Clinical Pearls for NEET-PG:** * **Kayser-Fleischer Ring:** Located in the Descemet’s membrane; starts superiorly, then inferiorly, then laterally. * **Vogt’s Striae:** Vertical stress lines in the stroma seen in Keratoconus. * **Stockers Line:** Iron deposition at the leading edge of a Pterygium. * **Chrysiasis** is usually asymptomatic and does not require treatment or discontinuation of the gold therapy, unlike copper deposition which indicates systemic toxicity.

Question 255: Which of the following is not a treatment modality for Keratoconus?

A. Spectacle
B. Prism (Correct Answer)
C. Contact lens
D. INTACS

Explanation: **Explanation:** Keratoconus is a progressive, non-inflammatory ectatic dystrophy characterized by paracentral thinning and cone-shaped protrusion of the cornea. This leads to **irregular myopic astigmatism**, which is the primary target of treatment. **Why Prism is the Correct Answer:** Prisms are used in ophthalmology to manage **diplopia (double vision)** caused by extraocular muscle imbalance or strabismus by shifting the image onto the fovea. They do not correct the irregular refractive errors or the structural thinning associated with Keratoconus. Therefore, prisms have no role in the management of this condition. **Analysis of Incorrect Options:** * **Spectacles:** In the early stages of Keratoconus, mild astigmatism and myopia can be corrected with glasses to provide functional vision. * **Contact Lenses:** These are the mainstay of treatment for moderate cases. **Rigid Gas Permeable (RGP)** lenses or Scleral lenses create a "tear lake" between the lens and the irregular cornea, effectively neutralizing the irregular astigmatism. * **INTACS (Intrastromal Corneal Ring Segments):** These are PMMA inserts placed in the deep corneal stroma to flatten the central cornea and reduce the "cone," improving visual acuity in patients intolerant to contact lenses. **Clinical Pearls for NEET-PG:** * **Gold Standard for Progression:** **CXL (Corneal Collagen Cross-linking)** using Riboflavin and UV-A light is the only treatment that stops the progression of Keratoconus. * **Surgical End-stage:** For advanced cases with scarring or extreme thinning, **Deep Anterior Lamellar Keratoplasty (DALK)** or Penetrating Keratoplasty (PK) is indicated. * **Classic Signs:** Munson’s sign (V-shaped lower lid on downgaze), Vogt’s striae (vertical stress lines), and Fleischer’s ring (iron deposition at the base of the cone).

Question 256: Megalocornea is associated with which of the following syndromes?

A. Down syndrome
B. Turner syndrome (Correct Answer)
C. Marfan syndrome
D. Ehlers-Danlos syndrome

Explanation: **Explanation:** **Megalocornea** is a non-progressive, bilateral condition defined by a horizontal corneal diameter of **≥13 mm** at birth or in adulthood, in the absence of elevated intraocular pressure. It is typically inherited as an X-linked recessive trait. 1. **Why Turner Syndrome is correct:** While Megalocornea is most commonly an isolated finding or associated with Marfan syndrome, it is a recognized systemic association of **Turner syndrome (45, XO)**. In the context of this specific question and standard ophthalmology textbooks (like Khurana), Turner syndrome is frequently cited alongside other associations like Alport syndrome and Down syndrome. 2. **Analysis of Incorrect Options:** * **Down Syndrome:** More commonly associated with **Keratoconus**, Brushfield spots, and infantile cataracts. * **Marfan Syndrome:** Classically associated with **Ectopia Lentis** (superotemporal subluxation) and high myopia. While Megalocornea *can* occur in Marfan, Turner syndrome is the specific association targeted in several NEET-PG pattern questions for this condition. * **Ehlers-Danlos Syndrome:** Primarily associated with **Keratoconus**, blue sclera, and **Keratoglobus** (generalized thinning and protrusion of the cornea). **Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** The most important differential for Megalocornea is **Buphthalmos (Congenital Glaucoma)**. In Megalocornea, the IOP is normal, the optic disc is normal, and there are no Haab striae. * **Systemic Associations (High-Yield):** Marfan syndrome, Turner syndrome, Alport syndrome, and Osteogenesis Imperfecta. * **Ocular Complications:** Patients are predisposed to **ectopia lentis** (due to zonular laxity) and early-onset cataract formation.

Question 257: All of the following are seen in Keratoconus EXCEPT?

A. Kayser-Fleischer ring (Correct Answer)
B. Progressive vision loss due to increasing myopia and irregular astigmatism
C. Scissoring reflex in retinoscopy
D. Munson sign positive

Explanation: **Explanation:** **Keratoconus** is a non-inflammatory, progressive thinning and cone-like ectasia of the cornea. **Why Option A is the Correct Answer:** The **Kayser-Fleischer (KF) ring** is a deposition of copper in the **Descemet’s membrane** of the peripheral cornea, characteristic of **Wilson’s disease**. In Keratoconus, the characteristic iron deposition ring is called the **Fleischer ring**, which occurs at the base of the cone. Confusing "Fleischer" with "Kayser-Fleischer" is a common trap in NEET-PG. **Analysis of Other Options:** * **Option B:** The hallmark of Keratoconus is progressive thinning and bulging, which leads to **progressive high myopia** and **irregular astigmatism**. * **Option C:** **Scissoring reflex** on retinoscopy is one of the earliest clinical signs, caused by the irregular curvature of the cornea. * **Option D:** **Munson’s sign** is a late clinical feature where the lower lid bulges in a V-shape when the patient looks down, due to the protruding corneal cone. **High-Yield Clinical Pearls for Keratoconus:** 1. **Vogt’s Striae:** Vertical stress lines in the deep stroma (disappear with digital pressure). 2. **Rizutti’s Sign:** Conical reflection on the nasal cornea when light is shone from the temporal side. 3. **Hydrops:** Acute corneal edema due to a rupture in the Descemet’s membrane. 4. **Oil Droplet Sign:** Seen on distant direct ophthalmoscopy. 5. **Association:** Often associated with Down syndrome, Atopic dermatitis, and Marfan syndrome. 6. **Treatment:** C3R (Corneal Collagen Cross-linking with Riboflavin) is the gold standard to stop progression.

Question 258: K-F ring is pathognomonic of which of the following conditions?

A. Cholestatic jaundice
B. Primary biliary cholangitis (PBC)
C. Hemochromatosis
D. Decreased ceruloplasmin level (Correct Answer)

Explanation: **Explanation:** The **Kayser-Fleischer (K-F) ring** is a classic ophthalmological sign characterized by a golden-brown or greenish-brown pigment deposition in the **Descemet’s membrane** of the peripheral cornea. It is caused by the deposition of excess **copper**. **Why Option D is Correct:** The K-F ring is most famously associated with **Wilson’s Disease** (Hepatolenticular degeneration). In Wilson’s disease, there is a deficiency of ATP7B (a copper-transporting ATPase), leading to impaired biliary excretion of copper and a failure to incorporate copper into ceruloplasmin. This results in **decreased serum ceruloplasmin levels** and the accumulation of free copper in various organs, including the liver, brain (basal ganglia), and the cornea (K-F ring). **Analysis of Incorrect Options:** * **A & B (Cholestatic Jaundice/PBC):** While K-F rings can rarely be seen in chronic cholestatic diseases (due to impaired biliary excretion of copper), they are not pathognomonic for these conditions. Wilson’s disease remains the primary association for exam purposes. * **C (Hemochromatosis):** This is a disorder of **iron** overload, not copper. Iron deposition in the eye typically presents as *siderosis bulbi*, not K-F rings. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** K-F rings start at the **Schwalbe’s line** and involve the **Descemet’s membrane**. * **Appearance:** They usually appear first in the superior pole, then inferior, and finally become circumferential. * **Detection:** While visible to the naked eye in advanced cases, a **Slit-lamp examination** is the gold standard for early detection. * **Reversibility:** The ring may disappear with effective chelation therapy (e.g., D-Penicillamine). * **Sunflower Cataract:** Another ocular feature of Wilson’s disease involving copper deposition in the anterior lens capsule.

Question 259: Corneal transparency is maintained by all except:

A. Relative dehydration
B. Increased mitotic figures in the centre of the cornea (Correct Answer)
C. Unmyelinated nerve fibers
D. Uniform spacing of collagen fibrils

Explanation: **Explanation:** Corneal transparency is a complex physiological state maintained by the unique anatomical arrangement and metabolic activity of the cornea. **Why Option B is the Correct Answer:** The corneal epithelium undergoes constant turnover, but cell division (mitosis) occurs primarily in the **limbus** (basal layer of the limbal epithelium), not the center. The presence of increased mitotic figures in the central cornea would disrupt the regular arrangement of epithelial cells and scatter light, thereby **decreasing** transparency. Furthermore, a high metabolic/mitotic rate in the center would interfere with the optical clarity required for vision. **Analysis of Incorrect Options:** * **A. Relative Dehydration:** The cornea is maintained in a state of "deturgescence" (78% water content). This is primarily achieved by the **Endothelial Sodium-Potassium ATPase pump**, which prevents stromal edema. Excess water disrupts the lattice arrangement, leading to opacity. * **C. Unmyelinated Nerve Fibers:** The cornea is highly innervated by the ophthalmic division of the trigeminal nerve. These fibers lose their myelin sheaths as they enter the corneal stroma. If they were myelinated, the lipid-rich sheaths would cause light scattering. * **D. Uniform Spacing of Collagen Fibrils:** According to **Maurice’s Lattice Theory**, collagen fibrils in the stroma are of uniform diameter and are arranged in a regular lattice with spacing less than half the wavelength of light (λ/2). This allows for destructive interference of scattered light and constructive interference of the direct light beam. **High-Yield Clinical Pearls for NEET-PG:** * **Goldmann’s Theory:** A modification of Maurice’s theory, stating that transparency is maintained as long as the fibrils are small and the distance between them is uniform. * **Endothelial Cell Count:** Normal is 2500–3000 cells/mm². If the count falls below **500 cells/mm²**, corneal decompensation and edema occur. * **Crystallins:** Soluble proteins in the corneal epithelium and keratocytes that help minimize light scattering at the cellular level.

Question 260: Keratomalacia is associated with which of the following infections?

A. Herpes simplex
B. Varicella zoster
C. Measles (Correct Answer)
D. Diphtheria

Explanation: **Explanation:** **Keratomalacia** is the most severe stage of **Xerophthalmia**, characterized by rapid, liquefactive necrosis of the corneal stroma. It typically occurs in children with severe Vitamin A deficiency. **Why Measles is the Correct Answer:** Measles (Rubeola) is a major precipitating factor for keratomalacia in developing countries. The infection causes a "triple threat" to the cornea: 1. **Metabolic Stress:** It acutely depletes systemic Vitamin A stores. 2. **Direct Damage:** The virus causes viral keratitis and conjunctivitis. 3. **Secondary Infection:** It leads to immunosuppression, predisposing the cornea to secondary bacterial or fungal infections. This combination leads to rapid corneal melting and perforation. **Analysis of Incorrect Options:** * **Herpes Simplex (HSV):** Typically causes dendritic or geographic ulcers and disciform keratitis. While it can cause stromal melting (necrotizing keratitis), it is not classically associated with the systemic nutritional deficiency defined as keratomalacia. * **Varicella Zoster (VZV):** Causes Herpes Zoster Ophthalmicus (HZO) characterized by pseudodendrites and neurotrophic keratopathy, but not the liquefactive necrosis seen in keratomalacia. * **Diphtheria:** *Corynebacterium diphtheriae* is known for causing **membranous conjunctivitis**. While it can lead to corneal ulceration, it is not the primary infectious trigger for keratomalacia. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** Keratomalacia is classified as **X3A** (involving <1/3 of the cornea) and **X3B** (involving >1/3 of the cornea). * **Bitot’s Spots (X1B):** Triangular, foamy patches on the bulbar conjunctiva (Corynebacterium xerosis). * **Treatment:** Immediate administration of Vitamin A (200,000 IU orally on days 0, 1, and 14) is life-saving and sight-saving. * **Measles Vaccine:** Is considered a key intervention in preventing nutritional blindness worldwide.

Practice by Chapter

Corneal Anatomy and Physiology

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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

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Corneal Dystrophies

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Keratoconus and Ectatic Disorders

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Corneal Transplantation

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Corneal Topography and Imaging

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Dry Eye Disease

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Corneal Trauma

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