Diseases of the Cornea Practice Questions

Q: Which of the following statements is NOT true regarding the corneal stroma?

Derives its oxygen from aqueous humor. ### Explanation The corneal stroma constitutes approximately 90% of the total corneal thickness. Understanding its physiology and anatomy is crucial for NEET-PG. **Why Option D is the Correct Answer (The False Statement):** The primary source of oxygen for the corneal stroma (and the cornea in general) is the **atmospheric oxygen** dissolved in the **pre-corneal tear film**. While the posterior layers receive some oxygen from the aqueous humor, the stroma relies heavily on atmospheric diffusion. When the eyes are closed, oxygen is supplied by the palpebral conjunctival capillaries. The aqueous humor primarily provides **glucose** and nutrients, not the bulk of the oxygen. **Analysis of Other Options:** * **Option A:** The central corneal thickness is approximately 520–540 μm. Since the stroma makes up about 90% of this, it measures roughly **500 μm**. * **Option B:** The stroma consists of lamellae made of collagen fibers. **Type I collagen** is the most abundant. Type VI helps in spacing, and Type IV is found in the basement membranes (though predominantly in Bowman’s and Descemet’s). * **Option C:** Due to the precise lattice arrangement of collagen fibrils (Maurice’s Theory) and their small diameter relative to the wavelength of light, the stroma is highly transparent, transmitting over **90% of visible light**. **High-Yield Clinical Pearls for NEET-PG:** * **Transparency:** Maintained by the "Lattice Theory" and the dehydrating action of the endothelial pump. * **Keratocytes:** These are the specialized fibroblasts found between stromal lamellae, essential for repair. * **Dua’s Layer:** A thin, tough layer (approx. 15 μm) located between the stroma and Descemet’s membrane, discovered recently. * **Corneal Edema:** If the endothelium fails, the stroma thickens, leading to loss of transparency (Ground-glass appearance).

Q: All of the following conditions result in loss of corneal sensations except?

Exposure keratitis. **Explanation:** Corneal sensation is primarily mediated by the **long ciliary nerves** (branches of the Ophthalmic division of the Trigeminal nerve). Loss of sensation (corneal anesthesia) occurs when these nerve endings are damaged by infection, high intraocular pressure, or surgical trauma. **Why Exposure Keratitis is the correct answer:** In **Exposure Keratitis**, the primary pathology is the drying of the cornea due to incomplete lid closure (lagophthalmos). Crucially, the corneal sensations remain **intact or may even be hypersensitive** in the early stages. The damage is mechanical and evaporative, not neurological. **Analysis of Incorrect Options:** * **Acute Congestive Glaucoma:** The sudden, massive rise in intraocular pressure (IOP) causes mechanical compression and edema of the corneal nerve endings, leading to a temporary loss of sensation. * **Dendritic Ulcer (Herpes Simplex Keratitis):** This is a classic cause of corneal anesthesia. The HSV virus resides in the trigeminal ganglion and causes neurotrophic damage to the corneal nerves during reactivation. * **Absolute Glaucoma:** This is the final stage of glaucoma where the eye is blind and the IOP is chronically very high. The prolonged high pressure leads to permanent degeneration of the corneal nerve plexus. **High-Yield Clinical Pearls for NEET-PG:** * **Common causes of reduced corneal sensation:** HSV Keratitis (most common), Diabetes Mellitus, Leprosy, Acoustic Neuroma (compressing the 5th nerve), and Topical anesthetic abuse. * **Cogan’s Syndrome:** Associated with interstitial keratitis but usually preserves sensation. * **Neurotrophic Ulcer:** A non-healing ulcer that occurs specifically *because* the cornea is anesthetic (loss of trophic factors). * **Testing:** Corneal reflex is tested using a wisp of cotton; the afferent limb is the **Trigeminal nerve (V1)** and the efferent limb is the **Facial nerve (VII)**.

Q: A patient develops red eye two days after an episode of malaria. What is the probable cause?

Viral keratitis. **Explanation:** The correct answer is **Viral Keratitis**, specifically **Herpes Simplex Keratitis (HSK)**. **Why Viral Keratitis is the correct answer:** Malaria is characterized by high-grade, intermittent fever (febrile episodes). High fever acts as a potent trigger for the reactivation of the latent **Herpes Simplex Virus (HSV)** residing in the trigeminal ganglion. Once reactivated, the virus travels down the ophthalmic nerve to the cornea, leading to the development of dendritic ulcers. In medical literature, these are often referred to as "fever blisters" or "cold sores" when occurring on the lips, but they manifest as viral keratitis in the eye. **Analysis of Incorrect Options:** * **A. Conjunctivitis:** While common, it is not specifically triggered by the high-fever episodes characteristic of malaria. * **B. Anterior Uveitis:** Though it can be associated with systemic infections, it is not the classic post-malarial ocular presentation. * **D. Endophthalmitis:** This is a severe intraocular inflammation usually following trauma or surgery; it is not a recognized complication of a febrile malarial episode. **NEET-PG High-Yield Pearls:** * **The "Fever" Connection:** Any systemic condition causing high fever (Malaria, Typhoid, Influenza) can trigger **Dendritic Keratitis**. * **Clinical Sign:** The hallmark of HSV keratitis is a **dendritic ulcer** with terminal bulbs, which stains with Rose Bengal (devitalized cells at the margin) and Fluorescein (central ulceration). * **Treatment Contraindication:** Never use topical steroids in active dendritic keratitis, as it can lead to a "geographic ulcer." * **Other Ocular Malarial Signs:** While keratitis is a post-febrile complication, acute malarial retinopathy (hemorrhages, whitening) is a key prognostic indicator in Cerebral Malaria.

Q: 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?

Fusarium. **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.

Q: Keratoconus is seen in which of the following conditions?

Down syndrome. **Explanation:** **Keratoconus** is a progressive, non-inflammatory ectatic corneal dystrophy characterized by thinning and cone-like protrusion of the cornea. **1. Why Down Syndrome (Trisomy 21) is correct:** Down syndrome is the most common chromosomal disorder associated with Keratoconus, occurring in approximately 5–15% of patients. The association is attributed to structural collagen abnormalities and a high incidence of chronic eye rubbing due to associated blepharitis and atopy, which mechanically weakens the corneal stroma. **2. Analysis of Incorrect Options:** * **Patau Syndrome (Trisomy 13):** Characterized by severe ocular malformations like microphthalmia, colobomas, and cyclopia, but not typically Keratoconus. * **Turner Syndrome (45, XO):** Associated with ocular findings like ptosis, strabismus, and blue sclera, but Keratoconus is not a classic feature. * **Weber Syndrome:** This is a midbrain stroke syndrome (CN III palsy with contralateral hemiplegia) and does not involve structural corneal pathologies. **3. Clinical Pearls for NEET-PG:** * **Mnemonics for Keratoconus Associations:** Remember **"T-DOME"** * **T:** Turner syndrome (Rarely, but Down is much more common) * **D:** **Down Syndrome** (Highest yield) * **O:** Osteogenesis Imperfecta * **M:** Marfan Syndrome * **E:** Ehlers-Danlos Syndrome / Atopic Dermatitis * **Key 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). * **Management:** RGP (Rigid Gas Permeable) lenses for vision; C3R (Corneal Collagen Cross-linking) to stop progression; Penetrating Keratoplasty for advanced cases.

Q: All of the following drugs are associated with corneal deposition except?

Antimony. **Explanation:** The correct answer is **Antimony**. This question tests your knowledge of systemic drugs that cause ocular toxicity, specifically **Corneal Verticillata (Vortex Keratopathy)**. **1. Why Antimony is the correct answer:** Antimony is a heavy metal used primarily in the treatment of Leishmaniasis. While it can have systemic side effects, it is **not** associated with corneal deposits. In contrast, heavy metals that *do* cause corneal deposits include Gold (Chrysiasis), Silver (Argyrosis), and Copper (Kayser-Fleischer ring). **2. Analysis of Incorrect Options:** * **Chloroquine:** A classic cause of **Corneal Verticillata**. It deposits in the basal corneal epithelium in a whorl-like pattern. While these deposits are usually asymptomatic and reversible, they serve as a marker for potential retinal toxicity (Bull’s eye maculopathy). * **Amiodarone:** This anti-arrhythmic drug is the **most common cause** of Corneal Verticillata. Deposits occur in nearly 100% of patients on long-term therapy (>400mg/day). They rarely affect vision but can cause "blue-green halos." * **Quinacrine:** An antimalarial and antiprotozoal drug that, like chloroquine, is well-documented to cause yellowish-brown whorl-like corneal epithelial deposits. **3. NEET-PG High-Yield Pearls:** * **Mnemonic for Corneal Verticillata (CHAI-T):** **C**hloroquine, **H**ydroxychloroquine, **A**miodarone, **I**ndomethacin, and **T**amoxifen. * **Fabry’s Disease:** The most important systemic disease associated with Corneal Verticillata (due to glycosphingolipid deposition). * **Gold Deposits:** Occur in the deep stroma (Chrysiasis). * **Iron Deposits:** Usually occur in the epithelium (e.g., Hudson-Stahli line, Fleischer ring in Keratoconus).

Q: What is the characteristic feature of Herpes Simplex Keratitis?

Dendritic ulcer. **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).

Q: The arrow marked sign is due to deposition of which substance?

Iron. ***Iron*** - The arrow-marked sign represents **iron (hemosiderin) deposition** in the corneal epithelium, commonly seen as various iron lines like **Hudson-Stähli line**, **Fleischer ring** in keratoconus, or **Stocker's line** in pterygium. - Iron deposition occurs due to **tear film pooling** and oxidation of iron from hemoglobin breakdown, appearing as brownish linear deposits. *Copper* - Copper deposition creates the **Kayser-Fleischer ring** in Wilson's disease, which appears as a golden-brown ring at the **Descemet's membrane** periphery, not as linear corneal epithelial deposits. - This ring is pathognomonic for **Wilson's disease** and involves **Descemet's membrane**, unlike the superficial epithelial iron lines shown. *Melanin* - Melanin pigmentation appears as **dark brown or black deposits** and is typically seen in conditions like **melanosis** or **nevus**. - Unlike iron deposits, melanin pigmentation doesn't form characteristic **linear patterns** and has different histological staining properties. *Magnesium* - Magnesium does **not cause characteristic corneal deposits** or pigmentation visible on slit-lamp examination. - There are **no known clinical signs** of magnesium deposition creating linear corneal markings like those indicated by the arrow.

Question 1

Which of the following statements is NOT true regarding the corneal stroma?

Accepted Answer

Derives its oxygen from aqueous humor

Answer

Measures 500 micrometers

Answer

Type 1 collagen is most abundant; types 4 & 6 are also found

Answer

Transmits 90% of incoming light

Question 2

All of the following conditions result in loss of corneal sensations except?

Accepted Answer

Exposure keratitis

Answer

Acute congestive glaucoma

Answer

Dendritic ulcer

Answer

Absolute glaucoma

Question 3

Corneal deposits are seen in all except?

Accepted Answer

Reis-Bucklers corneal dystrophy

Answer

Fuchs' endothelial dystrophy

Answer

Hunter syndrome

Answer

Hurler syndrome

Question 4

A patient develops red eye two days after an episode of malaria. What is the probable cause?

Accepted Answer

Viral keratitis

Answer

Conjunctivitis

Answer

Anterior uveitis

Answer

Endophthalmitis

Question 5

A Fleischer ring is a distinct feature of which of the following conditions?

Accepted Answer

Pterygium

Answer

Keratoconus

Answer

Congenital ocular melanosis

Answer

Congenital epithelial melanosis

Question 6

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?

Accepted Answer

Fusarium

Answer

Acanthamoeba

Answer

Corynebacterium diphtheriae

Answer

Streptococcus pneumoniae

Question 7

Keratoconus is seen in which of the following conditions?

Accepted Answer

Down syndrome

Answer

Patau syndrome

Answer

Turner syndrome

Answer

Weber syndrome

Question 8

All of the following drugs are associated with corneal deposition except?

Accepted Answer

Antimony

Answer

Chloroquine

Answer

Amiodarone

Answer

Quinacrine

Question 9

What is the characteristic feature of Herpes Simplex Keratitis?

Accepted Answer

Dendritic ulcer

Answer

Disciform keratitis

Answer

Haab's striae

Answer

Band keratopathy

Question 10

The arrow marked sign is due to deposition of which substance?

Accepted Answer

Iron

Answer

Copper

Answer

Melanin

Answer

Magnesium

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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