Diseases of the Cornea Practice Questions

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

Keratitis. **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).

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

Pertussis. **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).

Q: Thinning of the cornea occurs in which condition?

Keratoconus. **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.

Q: Satellite lesions on the cornea are typically seen in which type of ulcer?

Fungal ulcer. **Explanation:** **1. Why Fungal Ulcer is correct:** Satellite lesions are a hallmark clinical feature of **filamentous fungal keratitis** (most commonly caused by *Aspergillus* or *Fusarium*). These are small, discrete infiltrates located away from the main ulcer margin. They occur because fungal hyphae can penetrate deep into the corneal stroma and spread laterally, creating secondary foci of infection separate from the primary site. Other characteristic features include a dry, leathery appearance, feathery margins, and a fixed hypopyon. **2. Why other options are incorrect:** * **Viral/Herpetic Ulcer:** These typically present with **dendritic ulcers** (linear branching with terminal bulbs) or geographic ulcers. They are characterized by diminished corneal sensations rather than satellite lesions. * **Bacterial Ulcer:** These usually present as a well-defined, yellowish-white suppurative ulcer with an associated mobile hypopyon. The margins are typically distinct or shaggy (in *Pseudomonas*), but they do not form isolated satellite spots. **3. NEET-PG High-Yield Pearls:** * **Most common cause of Fungal Keratitis:** Trauma with vegetative matter (e.g., a branch or leaf). * **Immune Ring (Wessely Ring):** An annular infiltrate often seen in fungal or chronic herpetic keratitis due to antigen-antibody reaction. * **Diagnostic Gold Standard:** Potassium Hydroxide (**KOH**) mount showing hyphae; Culture on **Sabouraud’s Dextrose Agar (SDA)**. * **Treatment of choice:** Topical Natamycin (5%) or Voriconazole. * **Note:** Steroids are strictly contraindicated in fungal ulcers as they promote rapid fungal growth and corneal perforation.

Q: In which of the following layers of the cornea does iron deposition occur, resulting in the formation of a 'Hudson-Stahli line'?

Bowman's membrane. **Explanation:** The **Hudson-Stahli line** is a horizontal line of iron deposition (hemosiderin) found at the junction of the upper two-thirds and lower one-third of the cornea. **1. Why Bowman’s Membrane is Correct:** The iron deposition in a Hudson-Stahli line occurs specifically in the **basal layers of the corneal epithelium** and the underlying **Bowman’s membrane**. It is typically seen in elderly patients and is considered a physiological sign of corneal aging. It forms due to the pooling of tears at the line of lid closure during blinking, where the iron from the tear film (lactoferrin) precipitates over time. **2. Why Other Options are Incorrect:** * **Epithelium:** While iron is deposited in the basal epithelial cells, standard NEET-PG curriculum and clinical texts (like Kanski) emphasize **Bowman’s membrane** as the primary structural site for these pigmented lines. * **Descemet’s Membrane:** This layer is associated with copper deposition (Kayser-Fleischer ring) or silver (Argyrosis), but not typically iron lines. * **Endothelium:** This is the site for **Krukenberg spindles** (pigment from the iris), not iron lines. **3. High-Yield Clinical Pearls for NEET-PG:** Iron lines in the cornea are high-yield "spotters." Remember these specific associations: * **Hudson-Stahli Line:** Age-related; lower 1/3rd of cornea. * **Fleischer Ring:** Found at the base of the cone in **Keratoconus**. * **Ferry’s Line:** Found in front of a **Filtering Bleb** (post-glaucoma surgery). * **Stocker’s Line:** Found at the leading edge of a **Pterygium**. * **Kayser-Fleischer (KF) Ring:** Copper deposition in Descemet’s membrane (Wilson’s Disease).

Q: Exposure keratitis is not associated with which of the following conditions?

5th nerve paralysis. **Explanation:** **Exposure Keratitis** occurs due to the **mechanical inability of the eyelids to close properly (lagophthalmos)**, leading to excessive evaporation of the tear film and drying of the corneal epithelium. **Why 5th Nerve Paralysis is the Correct Answer:** The 5th cranial nerve (Trigeminal nerve) provides **sensory** innervation to the cornea. Paralysis of the 5th nerve leads to **Neurotrophic Keratitis**, not exposure keratitis. In neurotrophic keratitis, the cornea becomes anesthetic, leading to a loss of the blink reflex and poor epithelial healing, but the eyelids can still physically close. **Analysis of Incorrect Options:** * **7th Nerve Paralysis (Bell’s Palsy):** The 7th nerve (Facial nerve) innervates the **orbicularis oculi** muscle, which is responsible for eyelid closure. Paralysis leads to lagophthalmos, causing direct corneal exposure. * **Symblepharon:** This is the adhesion of the palpebral conjunctiva to the bulbar conjunctiva. These structural adhesions can physically tether the eyelids, preventing complete closure and leading to exposure. * **Ectropion:** This is the outward turning of the eyelid margin. It prevents the eyelid from apposing the globe correctly, leading to an unstable tear film and exposure of the lower corneal/conjunctival surface. **High-Yield Clinical Pearls for NEET-PG:** 1. **Key Distinction:** Exposure Keratitis = **Motor** failure (7th Nerve); Neurotrophic Keratitis = **Sensory** failure (5th Nerve). 2. **Bell’s Phenomenon:** An upward and outward rolling of the eyeball during closure. If Bell's phenomenon is healthy, it protects the cornea even in mild lagophthalmos. 3. **Management:** Initial treatment involves intensive lubrication; surgical intervention includes **Tarsorrhaphy** (sewing the eyelids together) to protect the ocular surface.

Q: Dendritic Keratitis is characteristic of which of the following?

Herpes virus. **Explanation:** **Dendritic Keratitis** is the hallmark clinical presentation of **Herpes Simplex Virus (HSV)** epithelial keratitis. The virus infects the corneal epithelial cells, leading to cell lysis and the formation of linear, branching (dendritic) ulcers. These ulcers are characterized by **terminal bulbs** (knob-like ends containing live virus) and stained brilliantly with **Fluorescein** (the floor) and **Rose Bengal** (the devitalized margins). A key diagnostic feature is **diminished corneal sensations** due to trigeminal nerve involvement. **Why other options are incorrect:** * **Pseudomonas:** Typically causes a rapidly progressing **bacterial keratitis** characterized by a "soupy" yellowish-green discharge and a large hypopyon. It is common in contact lens wearers. * **Streptococci:** *S. pneumoniae* often causes a circumscribed, serpiginous ulcer with a tendency for perforation, but it does not form dendritic patterns. * **Staphylococci:** Usually presents as a well-defined, grayish-white stromal infiltrate (often associated with chronic blepharitis), not a branching epithelial ulcer. **High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir. **Steroids are strictly contraindicated** in the dendritic stage as they can lead to "Geographic Ulcers." * **Geographic Ulcer:** An enlarged, amoeboid-shaped ulcer formed when dendritic ulcers coalesce, often due to inappropriate steroid use. * **Recurrence:** HSV remains latent in the **Trigeminal Ganglion** and can reactivate due to stress, fever, or UV exposure. * **Differential Diagnosis:** "Pseudo-dendrites" (lacking terminal bulbs) can be seen in *Acanthamoeba* keratitis, Herpes Zoster Ophthalmicus, or healing corneal abrasions.

Q: Which is the most metabolically active layer of the cornea?

Endothelium. The **corneal endothelium** is a single layer of hexagonal cells that serves as the most metabolically active part of the cornea. Its primary function is to maintain **corneal deturgescence** (a state of relative dehydration). It achieves this through active **ATP-dependent sodium-potassium pumps** ($Na^+/K^+$ ATPase), which constantly pump water out of the stroma into the aqueous humor [2]. This process is vital because an overhydrated stroma loses its transparency, leading to corneal edema and blindness [1]. **Analysis of Options:** * **Option A (Descemet's membrane):** This is the basement membrane of the endothelium. It is an acellular, elastic structure and is metabolically inactive. * **Option C (Connective tissue stroma):** Making up 90% of corneal thickness, it consists of collagen lamellae and keratocytes. While it provides structural integrity, its metabolic rate is significantly lower than the endothelium. * **Option D (Epithelium):** While the epithelium is regenerative and active, its metabolic demand is secondary to the endothelium [3]. It acts primarily as a physical barrier and lacks the intensive active transport mechanisms found in the endothelial layer. **High-Yield Clinical Pearls for NEET-PG:** * **Regeneration:** Unlike the epithelium, corneal endothelial cells **do not regenerate** in humans [1]. They compensate for cell loss by stretching and increasing in size (polymegathism). * **Critical Cell Count:** A healthy endothelium has ~3,000 cells/mm². If the count falls below **500–700 cells/mm²**, corneal decompensation and edema occur [1]. * **Fuchs’ Dystrophy:** A common clinical condition involving the progressive loss of these metabolically active endothelial cells [1].

Q: Khodadaust Line indicates:

Rejection of a corneal graft. ### Explanation **Khodadoust Line** is a hallmark clinical sign of **endothelial rejection** following a penetrating keratoplasty (corneal graft). #### Why Option B is Correct: The Khodadoust line represents a linear precipitate of inflammatory cells (lymphocytes) on the corneal endothelium. These cells typically start at a vascularized part of the limbus and migrate across the graft's endothelial surface. As the line advances, it destroys the donor endothelial cells, leading to localized corneal edema behind the line. It is a definitive sign of **Type IV (cell-mediated) hypersensitivity** rejection. #### Why Other Options are Incorrect: * **Option A:** Sympathetic ophthalmia is characterized by bilateral granulomatous panuveitis (Mutton-fat KPs and Dalen-Fuchs nodules), not a Khodadoust line. * **Option C:** Acute congestive glaucoma presents with corneal edema due to high intraocular pressure and "Halos," but the Khodadoust line is specific to immunological rejection, not pressure-induced damage. * **Option D:** Lesions at the optic chiasma typically present with visual field defects (e.g., Bitemporal Hemianopia) and have no correlation with corneal findings. #### High-Yield Clinical Pearls for NEET-PG: * **Krachmer’s Spots:** Subepithelial infiltrates seen in **epithelial rejection** of a corneal graft. * **Wessely Ring:** An immune ring in the cornea seen in HSK (Herpes Simplex Keratitis) or Acanthamoeba keratitis. * **Treatment:** The mainstay of treatment for graft rejection is **intensive topical corticosteroids** (e.g., 1% Prednisolone acetate hourly). * **Timeframe:** Graft rejection usually occurs at least 2 weeks to months after surgery (unlike primary graft failure, which occurs within 24–48 hours).

Question 1

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

Accepted Answer

Keratitis

Answer

Chalazion

Answer

Entropion

Answer

Stye

Question 2

Interstitial keratitis is caused by all of the following except?

Accepted Answer

Pertussis

Answer

Tuberculosis (TB)

Answer

Herpes Simplex Virus (HSV)

Answer

Epstein-Barr Virus (EBV)

Question 3

Thinning of the cornea occurs in which condition?

Accepted Answer

Keratoconus

Answer

Megalocornea

Answer

Bullous keratopathy

Answer

Endothelial dystrophy

Question 4

Satellite lesions on the cornea are typically seen in which type of ulcer?

Accepted Answer

Fungal ulcer

Answer

Viral ulcer

Answer

Bacterial ulcer

Answer

Herpetic ulcer

Question 5

A 30-year-old man presents with a 10-day history of decreased vision in his left eye. He reports trauma to his left eye with vegetative matter 10-15 days prior. Examination reveals an ulcerative corneal lesion with a raised, creamy infiltrate at the base. The ulcer margins are described as feathery and hyphate, with a few satellite lesions present. What is the most probable causative agent?

Accepted Answer

Fusarium

Answer

Acanthamoeba

Answer

Corynebacterium diphtheriae

Answer

Streptococcus pneumoniae

Question 6

In which of the following layers of the cornea does iron deposition occur, resulting in the formation of a 'Hudson-Stahli line'?

Accepted Answer

Bowman's membrane

Answer

Epithelium

Answer

Descemet's membrane

Answer

Endothelium

Question 7

Exposure keratitis is not associated with which of the following conditions?

Accepted Answer

5th nerve paralysis

Answer

7th nerve paralysis

Answer

Symblepharon

Answer

Ectropion

Question 8

Dendritic Keratitis is characteristic of which of the following?

Accepted Answer

Herpes virus

Answer

Pseudomonas

Answer

Streptococci

Answer

Staphylococci

Question 9

Which is the most metabolically active layer of the cornea?

Accepted Answer

Endothelium

Answer

Descemet's membrane

Answer

Connective tissue stroma

Answer

Epithelium

Question 10

Khodadaust Line indicates:

Accepted Answer

Rejection of a corneal graft

Answer

Sympathetic ophthalmia that has a poor prognosis

Answer

Poor prognosis of acute congestive glaucoma

Answer

Lesion at the optic chiasma

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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