Diseases of the Cornea Practice Questions

Q: Corneal ulcer is defined as?

Erosion of epithelium with underlying inflammation. **Explanation:** A **corneal ulcer** is defined as a breach in the continuity of the corneal epithelium associated with necrosis of the underlying corneal stroma (inflammation). 1. **Why Option C is correct:** For a lesion to be classified as an "ulcer," there must be two components: a loss of the protective epithelial layer and an active inflammatory response in the stroma. Without stromal involvement/inflammation, the condition is merely a superficial injury. 2. **Why other options are incorrect:** * **Option A (Erosion of epithelium only):** This is the definition of a **Corneal Erosion**. In an erosion, the epithelium is lost, but the underlying stroma remains healthy and clear without infiltration or necrosis. * **Option B & D (Endothelium involvement):** The endothelium is the innermost layer. Loss of endothelium leads to corneal edema (bullous keratopathy) but does not define an ulcer. While loss of sensation (Option D) is a feature of neurotrophic ulcers, it is not the definition of a corneal ulcer itself. **High-Yield Clinical Pearls for NEET-PG:** * **Hypopyon:** A collection of pus/WBCs in the anterior chamber, often seen in bacterial (sterile) or fungal (infected) ulcers. * **Acanthamoeba Ulcer:** Characterized by a "Ring Infiltrate" and severe pain out of proportion to clinical signs; common in contact lens users. * **Herpes Simplex Keratitis:** Presents as a "Dendritic ulcer" with terminal bulbs. It is stained by Fluorescein (bed) and Rose Bengal (margins). * **Fungal Ulcer:** Look for "Feathery margins," "Satellite lesions," and a dry, greyish-white appearance. Often follows trauma with vegetative matter.

Q: Which of the following methods is NOT used to measure corneal thickness?

Javal-Schiøtz method. **Explanation:** The measurement of corneal thickness is known as **Pachymetry**. The **Javal-Schiøtz method** is the correct answer because it is a technique used for **Keratometry**, not pachymetry. It measures the curvature of the anterior corneal surface to determine corneal power and astigmatism, but it cannot measure the depth or thickness of the corneal tissue. **Analysis of Options:** * **A. OCT (Optical Coherence Tomography):** Specifically, Anterior Segment OCT (AS-OCT) uses light waves to provide high-resolution cross-sectional images, allowing for precise, non-contact measurement of corneal thickness. * **B. Ultrasonography:** Ultrasound Pachymetry is considered the traditional **gold standard**. It uses a high-frequency (20 MHz) probe to measure the time taken for sound waves to reflect from the epithelium and endothelium. * **C. Orbscan:** This is a slit-scanning topography system that provides a global map of the cornea, measuring both the anterior and posterior surfaces to calculate thickness across the entire cornea. **High-Yield Clinical Pearls for NEET-PG:** * **Average Central Corneal Thickness (CCT):** Approximately **540–560 μm**. * **Glaucoma Correlation:** CCT is vital for accurate Intraocular Pressure (IOP) readings. A thin cornea leads to an underestimation of IOP, while a thick cornea leads to an overestimation (Goldmann Applanation Tonometry). * **Refractive Surgery:** A minimum residual stromal bed (usually >250 μm) must be maintained post-LASIK to prevent corneal ectasia. * **Optical Pachymetry:** Uses a slit-lamp attachment (e.g., Haag-Streit) based on the principle of optical sectioning.

Q: Which is the least commonly involved nerve in herpes zoster ophthalmicus?

Facial nerve. **Explanation:** **1. Why Facial Nerve is the Correct Answer:** Herpes Zoster Ophthalmicus (HZO) is caused by the reactivation of the Varicella-Zoster Virus (VZV) latent in the **Trigeminal (V) ganglion**. The virus typically involves the **Ophthalmic division (V1)** of the trigeminal nerve. The Facial nerve (CN VII) is a motor nerve to the muscles of facial expression and is not a branch of the trigeminal nerve. While CN VII can be involved in Ramsay Hunt Syndrome (Geniculate ganglion involvement), it is **not** a primary or common component of HZO. **2. Analysis of Incorrect Options (Branches of V1):** The Ophthalmic nerve (V1) divides into three main branches, all of which are commonly involved in HZO: * **Frontal Nerve:** The most frequently involved branch. It divides into the supraorbital and supratrochlear nerves, supplying the forehead and upper eyelid. * **Lacrimal Nerve:** Supplies the lacrimal gland and the lateral aspect of the upper eyelid. * **Nasociliary Nerve:** A critical branch because it supplies the eyeball (cornea, iris, ciliary body) via the long and short ciliary nerves. Involvement of this nerve is clinically signaled by **Hutchinson’s Sign** (vesicles on the tip or side of the nose). **3. High-Yield Clinical Pearls for NEET-PG:** * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicate nasociliary nerve involvement and carry a high risk (76%) of intraocular inflammation (keratitis/uveitis). * **Most common complication:** Post-herpetic neuralgia. * **Most common ocular finding:** Epithelial keratitis (pseudodendrites—unlike true dendrites of HSV, these lack terminal bulbs and stain poorly with fluorescein). * **Treatment:** Oral Acyclovir (800 mg 5 times daily for 7–10 days), ideally started within 72 hours of rash onset.

Q: Fleischer ring is characteristic of which condition?

Keratoconus. ### 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.

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

Dendritic Keratitis. **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."

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

Prism. **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).

Q: Copper deposition in the cornea leads to what finding?

Kayser-Fleischer ring. **Explanation:** The **Kayser-Fleischer (KF) ring** is the hallmark ocular manifestation of **Wilson’s Disease** (Hepatolenticular degeneration). This condition is characterized by a deficiency in ceruloplasmin, leading to the systemic accumulation of free copper. In the eye, copper is deposited specifically in the **Descemet’s membrane** of the peripheral cornea. It typically appears as a golden-brown or greenish-brown ring, starting superiorly, then inferiorly, and eventually becoming circumferential. It is best visualized using a slit-lamp examination. **Analysis of Incorrect Options:** * **Keratoconus:** A non-inflammatory, progressive thinning and cone-like protrusion of the cornea. While it features a "Fleischer ring" (iron deposition at the base of the cone), it is not caused by copper deposition. * **Keratoglobus:** A rare genetic condition characterized by generalized thinning and hemispherical protrusion of the entire cornea from birth; it is not associated with metallic deposits. * **Siderosis:** This refers to the intraocular deposition of **iron**, usually following a retained iron-containing foreign body. It leads to a rusty discoloration of the iris and lens (Siderosis bulbi), not a copper ring. **High-Yield Clinical Pearls for NEET-PG:** * **Location:** KF rings are found in the **Descemet’s membrane** (not the epithelium or stroma). * **Reversibility:** The ring may disappear with effective chelation therapy (e.g., D-Penicillamine). * **Sunflower Cataract:** Another ocular sign of Wilson’s disease where copper deposits in the **anterior lens capsule**. * **Chalcosis:** The term for tissue reaction to intraocular copper (e.g., from a copper-containing foreign body).

Q: Megalocornea is associated with which of the following syndromes?

Turner syndrome. **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.

Q: All of the following are seen in Keratoconus EXCEPT?

Kayser-Fleischer ring. **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 1

Corneal ulcer is defined as?

Accepted Answer

Erosion of epithelium with underlying inflammation

Answer

Erosion of epithelium only

Answer

Erosion of endothelium only

Answer

Loss of endothelium with loss of corneal sensation

Question 2

Which of the following methods is NOT used to measure corneal thickness?

Accepted Answer

Javal-Schiøtz method

Answer

OCT (Optical Coherence Tomography)

Answer

Ultrasonography

Answer

Orbscan

Question 3

Which is the least commonly involved nerve in herpes zoster ophthalmicus?

Accepted Answer

Facial nerve

Answer

Frontal nerve

Answer

Lacrimal nerve

Answer

Nasociliary nerve

Question 4

Fleischer ring is characteristic of which condition?

Accepted Answer

Keratoconus

Answer

Megalocornea

Answer

Diabetes

Answer

Chalcosis

Question 5

Corneal sensation is diminished in which of the following conditions?

Accepted Answer

Dendritic Keratitis

Answer

Band Keratopathy

Answer

Exposure Keratitis

Answer

Phlyctenular Keratitis

Question 6

All of the following are true about the layers of the cornea except?

Accepted Answer

Type 2 and type 4 collagen are present in Descemet's membrane.

Answer

Pre-Descemet's layer is also known as Dua's layer.

Answer

Corneal stroma is the thickest layer of the cornea.

Answer

The endothelium is responsible for maintaining the relatively dehydrated state of the cornea.

Question 7

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

Accepted Answer

Prism

Answer

Spectacle

Answer

Contact lens

Answer

INTACS

Question 8

Copper deposition in the cornea leads to what finding?

Accepted Answer

Kayser-Fleischer ring

Answer

Keratoconus

Answer

Keratoglobus

Answer

Siderosis

Question 9

Megalocornea is associated with which of the following syndromes?

Accepted Answer

Turner syndrome

Answer

Down syndrome

Answer

Marfan syndrome

Answer

Ehlers-Danlos syndrome

Question 10

All of the following are seen in Keratoconus EXCEPT?

Accepted Answer

Kayser-Fleischer ring

Answer

Progressive vision loss due to increasing myopia and irregular astigmatism

Answer

Scissoring reflex in retinoscopy

Answer

Munson sign positive

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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