Diseases of the Cornea Practice Questions

Q: Which of the following is not a cause for interstitial keratitis?

Pneumococcus. **Explanation:** **Interstitial Keratitis (IK)** is a chronic non-ulcerative inflammation of the corneal stroma, characterized by cellular infiltration and vascularization (neovascularization) without primary involvement of the epithelium or endothelium. It is primarily an **immune-mediated (Type IV hypersensitivity)** response to a systemic infection rather than a direct invasion by the pathogen. **Why Pneumococcus is the correct answer:** * **Pneumococcus (*Streptococcus pneumoniae*)** is a pyogenic bacterium that typically causes **acute bacterial keratitis** (hypopyon ulcers). It leads to rapid tissue destruction, suppuration, and ulceration of the corneal epithelium. It does not trigger the chronic, immune-mediated stromal inflammation characteristic of Interstitial Keratitis. **Why the other options are incorrect:** * **Syphilis:** The most common cause of IK. Congenital syphilis typically presents with bilateral IK (often part of Hutchinson’s triad), while acquired syphilis usually presents unilaterally. * **Tuberculosis:** A well-known cause of IK, usually presenting as a unilateral, peripheral sectoral inflammation. * **Leprosy:** Chronic infection by *Mycobacterium leprae* can lead to IK, often associated with thickened corneal nerves and avascular keratitis. **High-Yield Clinical Pearls for NEET-PG:** * **Hutchinson’s Triad:** Interstitial keratitis, Hutchinson’s teeth (notched incisors), and 8th nerve deafness. * **Salmon Patch Appearance:** A characteristic clinical sign of the active stage of syphilitic IK, caused by intense deep vascularization in the stroma. * **Ghost Vessels:** After the inflammation subsides, the cleared vessels remain as empty channels in the stroma, visible on slit-lamp examination. * **Other Causes:** Cogan syndrome (IK + vestibuloauditory symptoms), Sarcoidosis, and viral infections (HSV, VZV, Mumps).

Q: Band-shaped keratopathy is caused by deposition of which substance?

Calcium. **Explanation:** **Band-shaped Keratopathy (BSK)** is a degenerative condition characterized by the deposition of **calcium salts** (specifically hydroxyapatite) in the sub-epithelial layers of the cornea, primarily the **Bowman’s membrane**. **Why Calcium is correct:** The deposition occurs due to the precipitation of calcium salts in the interpalpebral fissure. This area is prone to CO₂ loss and subsequent localized increase in pH (alkalinity), which favors calcium precipitation. It typically presents as a horizontal "band" with a characteristic "Swiss-cheese appearance" due to holes where corneal nerves penetrate the Bowman’s layer. **Why other options are incorrect:** * **Amyloid:** Associated with Lattice corneal dystrophy or secondary localized amyloidosis, not BSK. * **Monosaccharide:** Not a standard corneal deposit. However, glucose metabolism issues relate to diabetic keratopathy, which involves basement membrane thickening, not band formation. * **Lipid:** Lipid keratopathy involves the deposition of fats (cholesterol/phospholipids), usually secondary to chronic inflammation or vascularization (e.g., Arcus senilis). **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Most commonly caused by chronic intraocular inflammation (**Chronic Uveitis**, especially in **Juvenile Idiopathic Arthritis**). Other causes include hypercalcemia (Hyperparathyroidism), chronic exposure to mercury/preservatives, and end-stage eye disease (Phthisis bulbi). * **Clinical Feature:** Starts at the periphery (limbus) but is separated by a **clear zone** of cornea. * **Treatment of Choice:** Chelation using **EDTA (Ethylenediamine tetraacetic acid)** followed by superficial keratectomy.

Q: Which organism can penetrate a normal cornea?

Neisseria gonorrhoeae. **Explanation:** The corneal epithelium acts as a formidable mechanical barrier against most pathogens. Most bacteria require a pre-existing epithelial defect (trauma, contact lens wear, or dry eye) to initiate an infection. However, a select group of organisms possesses specific virulence factors (proteolytic enzymes) that allow them to penetrate an **intact/normal corneal epithelium.** **Why Neisseria gonorrhoeae is correct:** *Neisseria gonorrhoeae* is the classic example of a pathogen capable of invading a healthy cornea. It can cause hyperacute purulent conjunctivitis, which rapidly progresses to corneal perforation if not treated aggressively. Other organisms with this unique capability include *Corynebacterium diphtheriae*, *Listeria monocytogenes*, and *Haemophilus aegyptius*. **Analysis of Incorrect Options:** * **Neisseria meningitidis:** While it belongs to the same genus, it is a rare cause of primary keratitis and typically does not exhibit the same aggressive epithelial penetration as *N. gonorrhoeae*. * **Mycobacterium tuberculosis & Mycobacterium leprae:** These organisms generally involve the cornea through secondary immune-mediated responses (e.g., interstitial keratitis or phlyctenular keratoconjunctivitis) or chronic contiguous spread, rather than direct penetration of a healthy epithelium. **NEET-PG High-Yield Pearls:** * **Mnemonic for organisms penetrating intact cornea:** "**CHNL**" (**C**orynebacterium, **H**aemophilus, **N**eisseria, **L**isteria). Some also include *Shigella*. * *N. gonorrhoeae* keratitis is a **medical emergency**; it can lead to corneal melting and perforation within 24–48 hours. * The most common cause of bacterial corneal ulcers overall is *Staphylococcus aureus*, but it **cannot** penetrate a healthy cornea. * Among fungi, *Fusarium* is known for its ability to penetrate deep into the stroma and even through an intact Descemet’s membrane.

Q: Which of the following statements about band-shaped keratopathy is true?

Sarcoidosis can be a cause.. **Band-shaped Keratopathy (BSK)** is a degenerative condition characterized by the deposition of **calcium salts** (hydroxyapatite) in the subepithelial layers, specifically the **Bowman’s membrane**, the anterior stroma, and the epithelial basement membrane. ### **Explanation of Options:** * **Option D (Correct):** BSK is associated with systemic conditions that cause **hypercalcemia**, such as **sarcoidosis**, hyperparathyroidism, vitamin D toxicity, and milk-alkali syndrome. Chronic ocular inflammation (like juvenile idiopathic arthritis-associated uveitis) and long-term exposure to mercurial preservatives are also common causes. * **Option A & B (Incorrect):** The hallmark of BSK is the deposition of **calcium**, not iron. Furthermore, this deposition occurs primarily in the **Bowman’s membrane**, not the Descemet’s membrane. (Note: Iron deposition in the cornea is seen in conditions like Fleischer rings in keratoconus or Hudson-Stahli lines). * **Option C (Incorrect):** Since the deposits are calcium-based, the treatment of choice is **chelation using EDTA** (Ethylenediamine tetraacetic acid), a calcium-chelating agent, followed by mechanical scraping (debridement). ### **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** It typically starts at the periphery (3 and 9 o’clock positions) and progresses centrally as a horizontal "band." * **Lucent Zones:** A characteristic feature is the presence of **clear "holes"** within the calcium plaque, which represent areas where corneal nerves pierce the Bowman’s membrane. * **Clear Margin:** There is always a distinct **clear zone** between the peripheral edge of the calcification and the limbus (due to the absence of Bowman's membrane at the limbus). * **Most Common Ocular Cause:** Chronic uveitis (especially in children with JIA).

Q: In Herpes zoster keratitis, which of the following clinical presentations is LEAST likely to occur?

Sclerokeratitis. **Explanation:** In **Herpes Zoster Ophthalmicus (HZO)**, the virus (Varicella-Zoster) affects the ophthalmic division of the trigeminal nerve. While it can involve almost every layer of the eye, the question asks for the **least likely** presentation among the options provided. **1. Why Sclerokeratitis is the correct answer:** While HZO can cause scleritis and keratitis independently, **Sclerokeratitis** (inflammation of the sclera that spreads to involve the adjacent cornea) is a relatively rare complication compared to the direct corneal and uveal manifestations. In the context of NEET-PG, HZO is classically associated with epithelial, stromal, and endothelial involvement rather than primary scleral-driven corneal disease. **2. Analysis of other options:** * **Pseudodendritic Keratitis (A):** This is a hallmark of HZO. Unlike the true dendrites of Herpes Simplex (HSV), these are elevated, stuck-on lesions without terminal bulbs and do not stain well with fluorescein. * **Anterior Uveitis with Endothelial Keratitis (B):** HZO frequently causes a hypertensive anterior uveitis (due to vasculitis) often accompanied by inflammation of the corneal endothelium. * **Endothelitis (D):** This is a common manifestation where the virus triggers an immune response at the endothelial level, leading to localized corneal edema and Keratic Precipitates (KPs). **Clinical Pearls for NEET-PG:** * **Hutchinson’s Sign:** Vesicles on the tip of the nose (involvement of the nasociliary nerve) strongly predict ocular involvement. * **HSV vs. HZO Dendrite:** HSV has **true dendrites** (central ulceration, terminal bulbs); HZO has **pseudodendrites** (tapered ends, no terminal bulbs). * **Treatment:** Oral Acyclovir (800 mg 5 times daily) is the mainstay for HZO, which is double the dose used for HSV. * **Neurotrophic Keratopathy:** A common late complication due to loss of corneal sensations.

Q: Important in Herpes simplex involvement of the eye are all EXCEPT:

Purulent discharge. **Explanation:** Herpes Simplex Virus (HSV) keratitis is a leading cause of corneal blindness. The correct answer is **Purulent discharge**, as this is a hallmark of **bacterial conjunctivitis/keratitis**, not viral infections. Viral infections typically present with watery (serous) discharge. **Why the other options are characteristic of HSV:** * **Type of lesion (Option A):** HSV is famous for its specific morphological patterns. The most common is the **dendritic ulcer** (linear, branching with terminal bulbs), which stains with Fluorescein. If treated with steroids, it can enlarge into a **geographic ulcer**. * **Corneal anaesthesia (Option B):** HSV is a neurotropic virus that resides in the trigeminal ganglion. Its replication leads to the destruction of corneal nerve endings, resulting in **marked corneal hypoesthesia or anesthesia**. This is a classic diagnostic sign. * **Iridocyclitis (Option C):** HSV can cause secondary anterior uveitis (iridocyclitis) either through direct viral invasion or an immunologic reaction. It is often associated with high intraocular pressure (hypertensive uveitis). **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** The floor of the dendritic ulcer stains with **Fluorescein**, while the virus-laden cells at the margins (terminal bulbs) stain with **Rose Bengal**. * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir gel is the gold standard. **Steroids are strictly contraindicated** in epithelial (dendritic) keratitis as they promote viral replication, leading to geographic ulcers. * **Recurrence:** HSV remains latent in the **Trigeminal (V) ganglion**. * **Disciform Keratitis:** This is a type of stromal involvement characterized by a central, disc-shaped area of corneal edema, thought to be a Type IV hypersensitivity reaction.

Q: A 20-year-old male presents with sudden onset left eye pain and vision loss. Examination reveals a hazy left cornea. Upon looking down, a bulge is noted in the lower eyelid. Retinoscopy demonstrates a scissoring reflex and a positive oil drop sign in both eyes. What is the diagnosis?

Keratoconus. **Explanation:** The clinical presentation is a classic case of **Keratoconus**, a non-inflammatory, progressive thinning and ectasia of the central or paracentral cornea. **Why Keratoconus is correct:** * **Munson’s Sign:** The "bulge in the lower eyelid upon looking down" is a pathognomonic sign caused by the cone-shaped cornea indenting the lid. * **Oil Drop Sign:** Seen on distant direct ophthalmoscopy, this represents the conical protrusion. * **Scissoring Reflex:** Observed during retinoscopy due to irregular astigmatism. * **Acute Hydrops:** The "sudden onset pain and vision loss with a hazy cornea" indicates a rupture in **Descemet’s membrane**, leading to stromal edema (Acute Hydrops), a known complication of keratoconus. **Why other options are incorrect:** * **Corneal Dystrophy:** These are typically bilateral, symmetrical, and slowly progressive without the specific conical bulging or Munson’s sign. * **Pathological Myopia:** While it causes vision loss and high refractive error, it involves posterior segment changes (e.g., Fuchs' spot, staphyloma) rather than corneal ectasia or Munson's sign. * **Keratoglobus:** This involves hemispherical protrusion and thinning of the *entire* cornea from limbus to limbus, rather than a localized cone. It rarely presents with acute hydrops. **High-Yield Clinical Pearls for NEET-PG:** * **Fleischer’s Ring:** Iron deposition at the base of the cone (best seen with Cobalt blue filter). * **Vogt’s Striae:** Vertical stress lines in the deep stroma. * **Rizutti’s Sign:** Conical reflection on the nasal cornea when light is shone from the temporal side. * **Management:** Early stages use spectacles/RGP lenses; **Collagen Cross-linking (CXL/C3R)** stops progression; Keratoplasty is for advanced cases. *Note: Steroids are contraindicated in acute hydrops.*

Q: Posterior polymorphous dystrophy is characterized by which of the following?

Corectopia. **Explanation:** **Posterior Polymorphous Dystrophy (PPMD)** is a rare, usually autosomal dominant, bilateral corneal dystrophy affecting the corneal endothelium and Descemet membrane. **Why Corectopia is Correct:** The hallmark of PPMD is the transformation of corneal endothelial cells into "epithelial-like" cells. These abnormal cells have a migratory property; they can grow across the trabecular meshwork and onto the surface of the iris. As these membranes contract, they pull the iris, leading to **corectopia** (displacement of the pupil), ectropion uveae, and peripheral anterior synechiae (PAS). This mechanism is similar to that seen in Iridocorneal Endothelial (ICE) syndrome. **Analysis of Incorrect Options:** * **B. Autosomal recessive inheritance:** PPMD is typically inherited in an **Autosomal Dominant** pattern (linked to mutations in *ZEB1*, *COL8A2*, or *OVOL2* genes). * **C. Blindness in over 90% of sufferers:** Most patients are asymptomatic and the condition is often stable. Only a small percentage develop significant corneal edema or secondary glaucoma leading to severe vision loss. * **D. Treatment with lamellar corneal grafts:** While severe cases require surgery, the standard is **Penetrating Keratoplasty (PK)** or **Endothelial Keratoplasty (DSEK/DMEK)**. Simple lamellar grafts (which replace only the stroma) do not address the underlying endothelial pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Vesicular lesions:** Characterized by "railroad track" or "snail track" opacities on the posterior cornea. * **Glaucoma:** Occurs in ~15% of cases due to membrane overgrowth in the angle. * **Differential Diagnosis:** Must be distinguished from **ICE Syndrome** (which is unilateral and non-hereditary) and **CHED** (Congenital Hereditary Endothelial Dystrophy).

Question 1

Which of the following is not a cause for interstitial keratitis?

Accepted Answer

Pneumococcus

Answer

Syphilis

Answer

Leprosy

Answer

Tuberculosis

Question 2

Band-shaped keratopathy is caused by deposition of which substance?

Accepted Answer

Calcium

Answer

Amyloid

Answer

Monosaccharide

Answer

Lipid

Question 3

Which organism can penetrate a normal cornea?

Accepted Answer

Neisseria gonorrhoeae

Answer

Mycobacterium tuberculosis

Answer

Neisseria meningitidis

Answer

Mycobacterium leprae

Question 4

The corneal transparency is maintained by –

Accepted Answer

Endothelium

Answer

Keratocytes

Answer

Bowman's membrane

Answer

Descemet's membrane

Question 5

Which of the following statements about band-shaped keratopathy is true?

Accepted Answer

Sarcoidosis can be a cause.

Answer

Iron deposition occurs in Bowman's membrane.

Answer

Calcium deposition occurs in Descemet's membrane.

Answer

Iron chelating agents are used for treatment.

Question 6

In Herpes zoster keratitis, which of the following clinical presentations is LEAST likely to occur?

Accepted Answer

Sclerokeratitis

Answer

Pseudodendritic keratitis

Answer

Anterior uveitis with endothelial keratitis

Answer

Endothelitis

Question 7

Important in Herpes simplex involvement of the eye are all EXCEPT:

Accepted Answer

Purulent discharge

Answer

Type of lesion

Answer

Corneal anaesthesia

Answer

Iridocyclitis

Question 8

Which is the metabolically active layer of the cornea?

Accepted Answer

Epithelium

Answer

Stroma

Answer

Descemet's membrane

Answer

None of the above

Question 9

A 20-year-old male presents with sudden onset left eye pain and vision loss. Examination reveals a hazy left cornea. Upon looking down, a bulge is noted in the lower eyelid. Retinoscopy demonstrates a scissoring reflex and a positive oil drop sign in both eyes. What is the diagnosis?

Accepted Answer

Keratoconus

Answer

Corneal dystrophy

Answer

Pathological myopia

Answer

Keratoglobus

Question 10

Posterior polymorphous dystrophy is characterized by which of the following?

Accepted Answer

Corectopia

Answer

Autosomal recessive inheritance

Answer

Blindness in over 90% of sufferers

Answer

Treatment with lamellar corneal grafts

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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