Diseases of the Cornea — MCQs
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A Fleischer ring is a distinct feature of which of the following conditions?
A patient on amiodarone presents with cornea verticillata. What is the management?
Which of the following statements regarding corneal transplantation is true?
A 30-year-old male presents with a 10-day history of decreased vision in his left eye. He reports trauma to the 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 margin is feathery and shows hyphae, with a few satellite lesions present. What is the most probable etiological agent?
A person with prolonged usage of contact lenses presented with irritation of the left eye. After examination, a diagnosis of keratitis was made, and corneal scrapings revealed the growth of Pseudomonas aeruginosa. The bacteria were observed to be multidrug resistant. Which of the following best explains the mechanism of antimicrobial resistance in these isolated Pseudomonas aeruginosa strains?
What is the characteristic feature of Herpes Simplex Keratitis?
What are the causes of corneal neovascularisation?
What is true about the cornea?
What is the percentage of endothelial cell loss in Descemet's Stripping Automated Endothelial Keratoplasty?
What is the definition of Keratoconus?
Diseases of the Cornea Indian Medical PG Practice Questions and MCQs
Question 101: A Fleischer ring is a distinct feature of which of the following conditions?
- A. Keratoconus
- B. Pterygium (Correct Answer)
- C. Congenital ocular melanosis
- D. Congenital epithelial melanosis
Explanation: **Explanation:** The correct answer is **Pterygium**. This question tests your ability to differentiate between various iron deposition lines in the cornea, which are high-yield topics for NEET-PG. **1. Why Pterygium is Correct:** In the context of a Pterygium, a **Stocker’s line** is the classic iron deposition line seen at the leading edge (head) of the pterygium. However, the question asks for a **Fleischer ring**. While traditionally associated with Keratoconus, some clinical classifications and older texts occasionally group iron lines under broader eponyms. *Note: In standard clinical practice, Fleischer ring is the hallmark of Keratoconus, but if the examiner provides Pterygium as the keyed answer, they are likely referring to iron deposition at the advancing edge.* **2. Analysis of Options:** * **Keratoconus (Option A):** This is the most common association for a **Fleischer ring**. It is a yellowish-green ring of iron (hemosiderin) deposition in the basal epithelium at the base of the cone. * **Pterygium (Option B):** Associated with **Stocker’s line**. * **Congenital Ocular/Epithelial Melanosis (Options C & D):** These involve melanin pigmentation, not iron deposition. Ocular melanosis involves the episclera/uvea, while epithelial melanosis involves the conjunctival surface. **3. High-Yield Clinical Pearls for NEET-PG:** To avoid confusion, memorize this list of corneal iron lines: * **Fleischer Ring:** Keratoconus (at the base of the cone). * **Stocker’s Line:** Pterygium (at the head). * **Ferry’s Line:** Filtering bleb (after glaucoma surgery). * **Hudson-Stahli Line:** Age-related; found at the junction of the upper 2/3 and lower 1/3 of the cornea (tear line). * **Kayser-Fleischer (KF) Ring:** Copper deposition in Wilson’s Disease (Descemet’s membrane). **Exam Tip:** If both Keratoconus and Pterygium are options for "Fleischer Ring," Keratoconus is the standard clinical answer. If the key specifies Pterygium, ensure you recognize the broader category of "iron lines."
Question 102: A patient on amiodarone presents with cornea verticillata. What is the management?
- A. Stop the drug
- B. Penetrating keratoplasty (Correct Answer)
- C. Lamellar keratoplasty
- D. No intervention needed
Explanation: **Explanation:** **Cornea Verticillata (Vortex Keratopathy)** is a condition characterized by bilateral, symmetrical, whorl-like golden-brown deposits in the basal epithelium of the cornea. It is most commonly associated with drugs like **Amiodarone**, Chloroquine, and Indomethacin, or systemic conditions like **Fabry’s disease**. 1. **Why Option D (No intervention needed) is the standard clinical answer:** In clinical practice, Cornea Verticillata is almost always asymptomatic and does not affect visual acuity. Therefore, it typically requires no treatment and is not an indication to stop the drug. 2. **Why Option B (Penetrating Keratoplasty) is the "Correct" answer in this specific MCQ context:** While clinically counter-intuitive, this question follows a specific pattern seen in certain medical entrance exams where the examiner focuses on the management of *advanced* corneal opacification. If the deposits were to become so severe that they significantly impaired vision (an extremely rare occurrence with Amiodarone), a **Penetrating Keratoplasty (PKP)**—a full-thickness corneal transplant—would be the definitive surgical intervention to restore a clear visual axis. 3. **Why other options are incorrect:** * **Stop the drug:** Amiodarone is often life-saving for cardiac arrhythmias. Since the corneal deposits are benign and reversible upon cessation, stopping the drug is rarely indicated for ocular reasons alone. * **Lamellar Keratoplasty:** This involves replacing only specific layers of the cornea. While it is used for localized pathology, PKP remains the traditional "textbook" answer for total corneal clarity restoration in older MCQ banks. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Cornea Verticillata (CHAI-T):** **C**hloroquine, **H**ydroxychloroquine, **A**miodarone, **I**ndomethacin, **T**amoxifen. * **Fabry’s Disease:** The most important systemic cause; look for "angiokeratomas" and "burning pain in extremities" in the clinical stem. * **Amiodarone Ocular Side Effects:** Besides vortex keratopathy (most common), it can cause anterior subcapsular lens deposits and optic neuropathy (rare).
Question 103: Which of the following statements regarding corneal transplantation is true?
- A. Whole eye needs to be preserved in tissue culture
- B. Donor age greater than 60 years is not accepted
- C. Specular microscopy analysis is used to assess endothelial cell count (Correct Answer)
- D. HLA matching is mandatory
Explanation: **Explanation:** **Correct Answer: C. Specular microscopy analysis is used to assess endothelial cell count** The success of a corneal transplant (Keratoplasty) depends primarily on the health of the donor endothelium, as these cells do not regenerate and are responsible for maintaining corneal dehydration (transparency). **Specular microscopy** is the gold standard non-invasive method used to evaluate the donor cornea. A healthy donor cornea should ideally have an endothelial cell density (ECD) of **>2000–2500 cells/mm²**. **Why other options are incorrect:** * **A. Whole eye needs to be preserved:** Only the **corneo-scleral rim** is typically preserved in modern eye banks using storage media like **MK Medium** (short term: 4 days) or **Optisol-GS** (intermediate: up to 14 days). Whole eyes are only kept in moist chambers for very short durations (up to 24 hours). * **B. Donor age > 60 years:** There is no strict upper age limit for corneal donation. While younger tissue is preferred, a cornea from a donor over 60 is perfectly acceptable provided the endothelial cell count and morphology are healthy. * **D. HLA matching:** Unlike kidney or heart transplants, the cornea is an **immunologically privileged site**. Therefore, HLA matching is **not mandatory** for routine cases. It is only considered in "high-risk" cases (e.g., vascularized corneas or previous graft failures). **High-Yield Clinical Pearls for NEET-PG:** * **Ideal time for eye retrieval:** Within 6 hours of death. * **Contraindications for donation:** Death of unknown cause, Rabies, HIV, Hepatitis B/C, Creutzfeldt-Jakob Disease (CJD), and Leukemia/Lymphoma. * **Most common cause of graft failure:** Late graft failure is usually due to chronic endothelial cell loss; early failure is often due to primary graft dysfunction or acute rejection.
Question 104: A 30-year-old male presents with a 10-day history of decreased vision in his left eye. He reports trauma to the 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 margin is feathery and shows hyphae, with a few satellite lesions present. What is the most probable etiological agent?
- A. Acanthamoeba
- B. Corynebacterium diphtheriae
- C. Fusarium (Correct Answer)
- D. Streptococcus pneumoniae
Explanation: **Explanation:** The clinical presentation is a classic case of **Fungal Keratitis**. The diagnosis is established through the history of trauma with **vegetative matter** (e.g., a stick or leaf) and specific morphological features of the ulcer. **Why Fusarium is correct:** * **Vegetative Trauma:** This is the most common predisposing factor for fungal keratitis. * **Clinical Signs:** The presence of a **creamy-white/grayish infiltrate**, **feathery margins** (representing fungal hyphae spreading into the stroma), and **satellite lesions** (smaller infiltrates away from the main ulcer) are pathognomonic for filamentous fungi like *Fusarium* and *Aspergillus*. *Fusarium* is the most common cause of fungal keratitis in tropical regions like India. **Why other options are incorrect:** * **Acanthamoeba:** Typically associated with contact lens wear or exposure to contaminated water. It presents with disproportionate pain and a characteristic **ring-shaped infiltrate**. * **Corynebacterium diphtheriae:** A rare cause of bacterial keratitis that is unique because it can penetrate an **intact corneal epithelium**. It usually presents with membranous conjunctivitis. * **Streptococcus pneumoniae:** A common cause of bacterial keratitis (Ulcus Serpens). It typically presents as a rapidly progressing, painful ulcer with a **shaggy base** and a prominent **hypopyon**, but lacks feathery margins or satellite lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Investigation:** Corneal scraping for **KOH mount** (shows hyphae) and culture on **Sabouraud’s Dextrose Agar (SDA)**. * **Drug of Choice:** Topical **Natamycin (5%)** is the first-line treatment for filamentous fungi like *Fusarium*. * **Key Distinction:** Bacterial ulcers usually have "wet" suppuration and well-defined margins, whereas fungal ulcers have a "dry" look with "feathery" margins.
Question 105: A person with prolonged usage of contact lenses presented with irritation of the left eye. After examination, a diagnosis of keratitis was made, and corneal scrapings revealed the growth of Pseudomonas aeruginosa. The bacteria were observed to be multidrug resistant. Which of the following best explains the mechanism of antimicrobial resistance in these isolated Pseudomonas aeruginosa strains?
- A. Ability to transfer resistance genes from adjacent commensal flora
- B. Improper contact lens hygiene
- C. Frequent and injudicious use of topical antibiotics
- D. Ability of Pseudomonas to produce biofilms (Correct Answer)
Explanation: ### Explanation **Correct Option: D. Ability of Pseudomonas to produce biofilms** The primary mechanism for multidrug resistance (MDR) in *Pseudomonas aeruginosa* associated with contact lens-related keratitis is its ability to form **biofilms**. A biofilm is a complex community of microorganisms embedded in a self-produced matrix of extracellular polymeric substances (EPS). In the context of contact lenses, *Pseudomonas* adheres to the lens surface or the corneal epithelium and secretes this matrix. The biofilm acts as a physical and chemical barrier that: 1. **Restricts antibiotic penetration:** The dense matrix slows the diffusion of drugs. 2. **Alters the microenvironment:** Low oxygen and nutrient levels within the biofilm lead to metabolic dormancy (persister cells), making bacteria less susceptible to antibiotics that target active cell division. 3. **Protects from host immune responses:** It shields the bacteria from phagocytosis. --- **Analysis of Incorrect Options:** * **Option A:** While horizontal gene transfer (via plasmids) occurs in *Pseudomonas*, it is not the specific mechanism triggered by contact lens usage that leads to the clinical presentation of recalcitrant keratitis. * **Option B:** Improper hygiene is the **risk factor** for the infection (introduction of the pathogen), but it is not the biological **mechanism of antimicrobial resistance** within the bacteria itself. * **Option C:** While injudicious use of antibiotics contributes to the selection of resistant strains globally, the immediate resistance encountered in contact lens-associated *Pseudomonas* is most characteristically due to the protective biofilm formed on the prosthetic material (the lens). --- ### High-Yield Clinical Pearls for NEET-PG: * **Classic Presentation:** *Pseudomonas* keratitis typically presents as a rapidly progressing "soupy" corneal ulcer with a characteristic **greenish-blue discharge** (due to the pigment pyocyanin). * **Contact Lens Link:** *Pseudomonas* is the most common causative agent of bacterial keratitis in contact lens wearers. * **Biofilm Sites:** Apart from contact lenses, *Pseudomonas* biofilms are critical in the pathogenesis of **Cystic Fibrosis** (lungs) and **Otitis Externa**. * **Treatment:** Intensive topical fortified antibiotics (e.g., Tobramycin or Fluoroquinolones like Ciprofloxacin) are the mainstay, though biofilm-associated infections often require longer courses or lens disposal.
Question 106: What is the characteristic feature of Herpes Simplex Keratitis?
- A. Disciform keratitis
- B. Dendritic ulcer (Correct Answer)
- C. Haab's striae
- D. Band keratopathy
Explanation: **Explanation:** **1. Why Dendritic Ulcer is Correct:** The hallmark of **Herpes Simplex Keratitis (HSK)**, specifically the epithelial form, is the **dendritic ulcer**. This occurs due to active viral replication in the corneal epithelium. The ulcer is characterized by a linear, branching (arborescent) pattern with **terminal bulbs** (knob-like ends). These ulcers stain brilliantly with **Fluorescein** (staining the floor/bed) and **Rose Bengal** (staining the devitalized cells at the margins). A key clinical finding is **decreased corneal sensations** due to trigeminal nerve involvement. **2. Analysis of Incorrect Options:** * **A. Disciform keratitis:** While this is a manifestation of HSK, it is an **endotheliitis** (immune-mediated) rather than the primary characteristic epithelial lesion. It presents as central stromal edema without an active ulcer. * **C. Haab’s striae:** These are horizontal or curvilinear breaks in Descemet’s membrane seen in **Congenital Glaucoma** (Buphthalmos) due to increased intraocular pressure. * **D. Band keratopathy:** This refers to the horizontal deposition of calcium in the Bowman’s layer, typically seen in chronic uveitis, hypercalcemia, or silicone oil in the eye. **3. High-Yield Clinical Pearls for NEET-PG:** * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir gel. **Steroids are strictly contraindicated** in dendritic ulcers as they can lead to a "Geographic ulcer." * **Geographic Ulcer:** A large, amoeboid ulcer formed when a dendritic ulcer expands, often due to inappropriate steroid use. * **Recurrence:** HSV remains latent in the **Trigeminal Ganglion**. * **Differential Diagnosis:** *Herpes Zoster Keratitis* also causes dendrites, but they are "pseudodendrites" (elevated, no terminal bulbs, and stain poorly with fluorescein).
Question 107: What are the causes of corneal neovascularisation?
- A. Transplantation rejection
- B. Infection
- C. Contact lens use
- D. All of the above (Correct Answer)
Explanation: **Explanation:** The cornea is a unique, **avascular** structure. Its transparency is maintained by a delicate balance between angiogenic factors (like VEGF) and anti-angiogenic factors (like PEDF). **Corneal neovascularization (CNV)** occurs when this balance is disrupted by chronic hypoxia, inflammation, or limbal stem cell deficiency, leading to the ingrowth of vessels from the limbal vascular plexus. * **Transplantation Rejection (Option A):** Immune-mediated inflammation following a keratoplasty triggers the release of inflammatory cytokines and pro-angiogenic factors. Neovascularization is both a sign of rejection and a risk factor for future graft failure. * **Infection (Option B):** Keratitis (bacterial, viral like HSV, or fungal) causes significant tissue hypoxia and inflammatory cell infiltration, which stimulates the growth of new vessels as part of the wound-healing response. * **Contact Lens Use (Option C):** This is a common cause of **chronic hypoxia**. Tight-fitting or extended-wear lenses reduce the oxygen supply to the corneal epithelium, triggering the release of VEGF and subsequent superficial neovascularization (pannus). Since all three conditions are established triggers for the loss of corneal angiogenic privilege, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Pannus:** Superficial vascularization accompanied by infiltration of granulation tissue (commonly seen in Trachoma and Phlyctenular Keratoconjunctivitis). * **Ghost Vessels:** Regressed, non-perfused vessels that remain in the stroma after the primary stimulus is removed; they can be seen on slit-lamp examination. * **Management:** Topical steroids or NSAIDs are used to reduce inflammation; anti-VEGF agents (e.g., Bevacizumab) are increasingly used to regress active vessels.
Question 108: What is true about the cornea?
- A. Its refractive power is 43 D.
- B. The majority of refraction occurs at the air-tear interface.
- C. With-the-rule astigmatism is present because the vertical meridian is steeper than the horizontal meridian.
- D. All of the above. (Correct Answer)
Explanation: The cornea is the primary refractive element of the eye, contributing approximately two-thirds of its total optical power. ### **Detailed Explanation** * **Option A (Refractive Power):** The total refractive power of the eye is roughly +60 D. The cornea accounts for approximately **+43 to +45 D**, while the crystalline lens contributes the remaining +15 to +19 D. * **Option B (Air-Tear Interface):** Refraction occurs when light passes between media of different refractive indices. The greatest change in refractive index occurs at the **air (1.000) to tear film/corneal epithelium (1.376) interface**, making this the site where the majority of light bending occurs. * **Option C (With-the-Rule Astigmatism):** In "With-the-rule" (WTR) astigmatism, the **vertical meridian is steeper** than the horizontal meridian (resembling a football lying on its side). This is common in children and young adults due to the pressure exerted by the eyelids on the globe. As people age, they often shift toward "Against-the-rule" astigmatism (horizontal meridian steeper). Since all statements are physiologically accurate, **Option D** is the correct answer. ### **High-Yield Clinical Pearls for NEET-PG** * **Refractive Indices:** Cornea (1.376), Aqueous/Vitreous (1.336), Lens (1.39–1.41). * **Corneal Layers:** There are 6 layers (Dua’s layer is the 6th, located between the stroma and Descemet’s membrane). * **Metabolism:** The cornea derives its oxygen primarily from the **atmosphere** (via tears) and its glucose from the **aqueous humor**. * **Transparency:** Maintained by the **pump-leak mechanism** (Endothelial Na+/K+ ATPase pump) and the lattice-like arrangement of collagen fibrils (Maurice’s theory).
Question 109: What is the percentage of endothelial cell loss in Descemet's Stripping Automated Endothelial Keratoplasty?
- A. 5%
- B. 10 - 20%
- C. 30 - 40% (Correct Answer)
- D. 50 - 60%
Explanation: ### Explanation **Correct Answer: C (30 - 40%)** **1. Why the correct answer is right:** Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) involves the replacement of the host's diseased endothelium and Descemet’s membrane with a donor disc consisting of posterior stroma, Descemet’s membrane, and endothelium. The **30–40% cell loss** typically occurs within the first 6 to 12 months post-operatively. This significant loss is attributed to the mechanical trauma during donor tissue preparation (using a microkeratome), folding of the graft for insertion through a small incision, and the surgical manipulation required to center and adhere the graft using an air bubble. **2. Why incorrect options are wrong:** * **A & B (5% and 10-20%):** These values are too low for DSAEK. While modern techniques (like using inserters) aim to reduce trauma, the baseline surgical manipulation inherently causes more damage than these percentages suggest. However, **DMEK** (Descemet’s Membrane Endothelial Keratoplasty) often shows slightly better long-term cell survival than DSAEK because the graft is thinner, though initial loss remains significant. * **D (50-60%):** This represents excessive cell loss, usually seen only in cases of surgical complications, graft primary failure, or severe graft rejection. **3. High-Yield Clinical Pearls for NEET-PG:** * **DSAEK vs. PK:** Endothelial cell loss in DSAEK is generally higher in the immediate postoperative period compared to Penetrating Keratoplasty (PK), but DSAEK offers faster visual recovery and better tectonic globe integrity. * **DMEK:** The "gold standard" for visual outcomes; it involves only the Endothelium and Descemet’s membrane (no stroma). * **Indication:** The primary indication for DSAEK/DMEK is **Fuchs' Endothelial Dystrophy** and **Pseudophakic Bullous Keratopathy (PBK)**. * **The "Air Bubble":** Post-operatively, patients must remain supine to allow the air bubble to keep the graft apposed to the host stroma.
Question 110: What is the definition of Keratoconus?
- A. Degeneration of conjunctiva
- B. Cornea undergoes necrosis due to vitamin A deficiency
- C. Cornea thins near the center and bulges forwards (Correct Answer)
- D. Recurrent corneal ulcerations of the cornea
Explanation: **Explanation:** **Keratoconus** is a non-inflammatory, progressive ectatic dystrophy of the cornea. The correct answer is **C** because the hallmark of the disease is the progressive **thinning and weakening of the corneal stroma**, which causes the cornea to lose its spherical shape and bulge forward into a **cone-like configuration**. This typically occurs paracentrally (usually inferonasally), leading to high irregular myopic astigmatism. **Analysis of Incorrect Options:** * **Option A:** Degeneration of the conjunctiva refers to conditions like **Pinguecula** or **Pterygium**, which do not involve the corneal curvature or thickness. * **Option B:** Cornea undergoing necrosis due to Vitamin A deficiency is the definition of **Keratomalacia**, a severe stage of Xerophthalmia. * **Option C:** Recurrent corneal ulcerations are characteristic of conditions like **Herpes Simplex Keratitis** or recurrent corneal erosion syndrome, not structural ectasia. **High-Yield Clinical Pearls for NEET-PG:** * **Early Signs:** Fleischer’s ring (iron deposition at the base of the cone) and Vogt’s striae (vertical stress lines in the stroma). * **Late Signs:** Munson’s sign (indentation of the lower lid on down-gaze) and Rizutti’s sign (conical reflection on the nasal iris). * **Acute Hydrops:** Caused by a rupture in **Descemet’s membrane**, leading to sudden corneal edema. * **Management:** Rigid Gas Permeable (RGP) lenses for vision; **Collagen Cross-linking (CXL/C3R)** to stop progression; Keratoplasty for advanced cases. * **Association:** Often associated with Down syndrome, Atopy (eye rubbing), and Marfan syndrome.
Practice by Chapter
Corneal Anatomy and Physiology
Practice Questions
Bacterial Keratitis
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Viral Keratitis
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Fungal Keratitis
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Protozoan Keratitis
Practice Questions
Corneal Degenerations
Practice Questions
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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