Diseases of the Cornea Practice Questions

Q: A patient presents to the eye outpatient department with disc-shaped edema over the cornea. The patient has a history of vesicles over the lips a few weeks prior. There is no ulceration upon staining. What is the most likely diagnosis?

Disciform viral keratitis. ### Explanation The clinical presentation of **disc-shaped corneal edema** (disciform keratitis) following a history of **vesicles over the lips** (suggestive of Herpes Simplex Virus - Labialis) is a classic description of **Disciform Viral Keratitis**. **1. Why Option A is Correct:** Disciform keratitis is a form of **endotheliitis** caused by a delayed-type hypersensitivity reaction (Type IV) to the Herpes Simplex Virus (HSV) antigen. Unlike epithelial keratitis, there is **no active viral replication** in the epithelium, which explains why there is **no ulceration** upon staining. The hallmark clinical sign is a central or paracentral zone of stromal edema with an intact epithelium, often accompanied by "keratic precipitates" (KPs) underlying the edema. **2. Why Other Options are Incorrect:** * **Option B (Marginal Ulcer):** These are typically hypersensitivity reactions to Staphylococcal exotoxins. They present as peripheral infiltrates with a clear space between the limbus and the ulcer, not as central disciform edema. * **Option C (Metaherpetic/Trophic Keratitis):** This is a mechanical failure of epithelial healing due to basement membrane damage and loss of corneal sensations (neurotrophic). It presents as a **non-healing ulcer** with smooth, rounded borders, which contradicts the "no ulceration" finding in this case. **Clinical Pearls for NEET-PG:** * **Gold Standard Treatment:** Topical steroids (to control the immune response) combined with prophylactic topical antivirals (to prevent viral reactivation). * **Wessely Ring:** An immune ring of stromal precipitation sometimes seen in disciform keratitis. * **Sensation:** Corneal sensations are typically **reduced** in HSV infections. * **Dendritic Ulcer:** The most common presentation of primary/recurrent epithelial HSV; it stains with Fluorescein (bed) and Rose Bengal (edges).

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).

Question 1

A patient presents to the eye outpatient department with disc-shaped edema over the cornea. The patient has a history of vesicles over the lips a few weeks prior. There is no ulceration upon staining. What is the most likely diagnosis?

Accepted Answer

Disciform viral keratitis

Answer

Marginal ulcer

Answer

Metherpetiform keratitis

Answer

None of the above

Question 2

Hypopyon ulcer may be produced by which of the following organisms?

Accepted Answer

All of the above

Answer

Pneumococcus

Answer

Pseudomonas

Answer

Gonococcus

Question 3

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 4

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 5

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 6

Fleischer ring is characteristic of which condition?

Accepted Answer

Keratoconus

Answer

Megalocornea

Answer

Diabetes

Answer

Chalcosis

Question 7

Corneal sensation is diminished in which of the following conditions?

Accepted Answer

Dendritic Keratitis

Answer

Band Keratopathy

Answer

Exposure Keratitis

Answer

Phlyctenular Keratitis

Question 8

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 9

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

Accepted Answer

Prism

Answer

Spectacle

Answer

Contact lens

Answer

INTACS

Question 10

Copper deposition in the cornea leads to what finding?

Accepted Answer

Kayser-Fleischer ring

Answer

Keratoconus

Answer

Keratoglobus

Answer

Siderosis

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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