Diseases of the Cornea Practice Questions

Q: Which of the following is NOT true regarding the treatment of bacterial corneal ulcer?

Steroids are usually given in persistent epithelial defects. **Explanation:** In the management of bacterial corneal ulcers, the primary goal is to eliminate the pathogen and promote healing. **Option D is the correct answer (the false statement)** because steroids are generally **contraindicated** in the presence of an active infection or a persistent epithelial defect. Steroids inhibit collagen synthesis and fibroblast activity, which delays epithelialization and increases the risk of corneal melting and perforation. They should only be considered under strict supervision once the infection is controlled and the epithelium is intact. **Analysis of other options:** * **Option A:** Fortified antibiotics (e.g., Tobramycin 1.4% or Cefazolin 5%) are the **gold standard** for treating severe bacterial ulcers, providing higher drug concentrations than commercially available drops. * **Option B:** Cycloplegics (like Atropine or Homatropine) are essential to relieve ciliary spasms (reducing pain) and to prevent the formation of posterior synechiae by keeping the pupil mobile. * **Option C:** For small corneal perforations (<2mm) or impending perforations, **Cyanoacrylate glue** (tissue adhesive) with a bandage contact lens is a standard intervention to maintain anterior chamber integrity. **NEET-PG High-Yield Pearls:** * **Most common causative organism:** *Staphylococcus aureus* (overall); *Pseudomonas* (contact lens users). * **Hypopyon** in bacterial ulcers is typically **sterile** (due to toxins, not direct bacterial invasion). * **Steroid use rule:** Never use steroids if the ulcer is fungal or if a dendritic (Herpetic) lesion is present. * **Vitamin C** supplementation is often given to promote collagen synthesis and healing.

Q: Keratomalacia includes the following except?

Severe pain in the eye. **Explanation:** **Keratomalacia** is the most severe stage of Vitamin A deficiency (Xerophthalmia), characterized by the liquefactive necrosis of the cornea. **Why "Severe pain in the eye" is the correct answer:** The hallmark of Keratomalacia is that it is a **painless** condition. This occurs because Vitamin A deficiency leads to **corneal xerosis (dryness)** and a loss of corneal sensation (anesthesia). Because the cornea becomes insensitive, even extensive melting and perforation occur without the typical inflammatory pain associated with other types of keratitis. **Analysis of Incorrect Options:** * **Night Blindness (Nyctalopia):** This is the earliest clinical symptom of Vitamin A deficiency (WHO Grade XN). It occurs due to the failure of rhodopsin regeneration in the rod cells. * **Xerosis of the Cornea:** This is a precursor to Keratomalacia. The cornea appears dull, lusterless, and "dry-leather" like due to the loss of goblet cells and keratinization of the epithelium. * **Perforation of Cornea:** Keratomalacia involves rapid "melting" of the corneal stroma. If untreated, this leads to descemetocele formation and eventual perforation, often resulting in endophthalmitis or phthisis bulbi. **Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** * X1A: Conjunctival xerosis * X1B: **Bitot’s spots** (foamy deposits on bulbar conjunctiva) * X2: Corneal xerosis * X3A: Keratomalacia ( 1/3rd corneal surface) * **Treatment:** Immediate administration of Vitamin A (200,000 IU orally on days 0, 1, and 14). * **Key Differentiator:** Unlike bacterial ulcers, Keratomalacia presents with a **quiet eye** (no redness or ciliary congestion) despite the severity of the melting.

Q: Keratomalacia is a clinical manifestation associated with which of the following conditions?

Diarrheal diseases. **Explanation:** **Keratomalacia** is the most severe ocular manifestation of **Vitamin A deficiency (Xerophthalmia)**, characterized by rapid, liquefactive necrosis of the corneal stroma. **Why Diarrheal Diseases are correct:** Vitamin A is a fat-soluble vitamin that requires adequate intestinal absorption and a healthy liver for storage (as retinol palmitate). **Diarrheal diseases**, particularly chronic diarrhea or malabsorption syndromes (like Celiac disease or cystic fibrosis), lead to a significant loss of nutrients and impaired absorption. In children, acute gastroenteritis often acts as a "precipitating factor" that depletes already low Vitamin A stores, leading to the rapid onset of keratomalacia. **Why other options are incorrect:** * **Varicella (Chickenpox):** While it can cause viral keratitis or uveitis, it is not a primary cause of the systemic nutritional deficiency required to produce keratomalacia. * **Mumps:** This typically presents with dacryoadenitis (inflammation of the lacrimal gland) or optic neuritis, but does not cause corneal liquefaction. **Clinical Pearls for NEET-PG:** * **WHO Classification of Xerophthalmia:** Keratomalacia is classified as **X3A** (involving 1/3 of the cornea). * **Bitot’s Spots (X1B):** These are triangular, foamy, silvery-white patches on the bulbar conjunctiva (usually temporal) caused by *Corynebacterium xerosis*. * **The "Silent" Ulcer:** Keratomalacia is often painless and lacks significant inflammation (ciliary congestion) because the cornea is necrotic and the eye is "quiet." * **Treatment:** Immediate administration of Vitamin A (200,000 IU orally on days 0, 1, and 14) is critical to save the fellow eye and the child's life, as keratomalacia is a marker of high systemic mortality.

Q: In Keratoconus, all are seen except?

Hypermetropic refractive error. **Explanation:** **Keratoconus** is a non-inflammatory, progressive ectatic dystrophy characterized by localized thinning and protrusion of the cornea, typically assuming a conical shape. **Why Option D is the correct answer:** In Keratoconus, the cornea becomes increasingly **steep** and conical. According to optical principles, a steeper corneal curvature increases the refractive power of the eye, leading to **Progressive Myopia** and **Irregular Astigmatism**. Hypermetropia (farsightedness) is not a feature of keratoconus; rather, it is the opposite of the refractive change observed. **Analysis of incorrect options:** * **Munson’s Sign (Option A):** This is a classic late-stage clinical sign where the lower eyelid bulges in a V-shape when the patient looks downward, caused by the cone-shaped cornea. * **Thinning of the cornea (Option B):** The hallmark of the disease is progressive **stromal thinning**, most commonly involving the paracentral or central area, leading to corneal protrusion. * **Distortion of corneal reflex (Option C):** Due to the irregular curvature (ectasia), the normal circular corneal light reflex becomes distorted. This is easily visualized using a Placido disc or Keratoscopy (showing irregular, crowded mires). **High-Yield Clinical Pearls for NEET-PG:** 1. **Early Sign:** "Scissoring reflex" on retinoscopy and "Oil droplet sign" (Charleux sign) on distant direct ophthalmoscopy. 2. **Vogt’s Striae:** Vertical stress lines in the deep stroma/Descemet’s membrane that disappear with digital pressure. 3. **Fleischer’s Ring:** Iron deposition in the basal epithelium at the base of the cone (best seen with a cobalt blue filter). 4. **Hydrops:** Sudden profound vision loss due to a rupture in Descemet’s membrane, leading to acute corneal edema. 5. **Associations:** Down syndrome, Atopy (eye rubbing), Marfan syndrome, and Ehlers-Danlos syndrome.

Q: What is the diagnostic test for a corneal ulcer?

Sodium fluorescein dye. **Explanation:** The diagnosis of a corneal ulcer (epithelial defect) is clinically confirmed using **Sodium Fluorescein dye (2%)**. **1. Why Sodium Fluorescein is the Correct Answer:** The corneal epithelium is lipophilic and normally acts as a barrier to water-soluble dyes. When there is a breach in the epithelium (as seen in a corneal ulcer), the underlying **hydrophilic stroma** is exposed. Fluorescein dye, being water-soluble, is absorbed by the stroma and glows a **brilliant green** under cobalt blue light. This clearly demarcates the area of the ulcer. **2. Analysis of Incorrect Options:** * **Methylene Blue:** This is primarily used to stain the lacrimal sac during Dacryocystorhinostomy (DCR) or to mark the skin before surgery. It is not used for routine corneal staining. * **Alcian Blue:** This dye has an affinity for mucin. It is used to stain excess mucus in the tear film, often seen in cases of Keratoconjunctivitis Sicca (Dry Eye). * **Rose Bengal:** This dye stains **devitalized (dead/dying) cells** and mucus. While it can stain the edges of a dendritic ulcer (Herpes Simplex Keratitis), it is highly irritating to the eye and has largely been replaced by Lissamine Green. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dendritic Ulcer:** Stains with Fluorescein (the floor/bed of the ulcer) and Rose Bengal (the swollen epithelial cells at the margins). * **Seidel’s Test:** Uses Fluorescein to detect aqueous leakage from a penetrating ocular injury (positive if the dye is diluted/washed away by clear fluid). * **Lissamine Green:** Similar to Rose Bengal (stains dead cells) but is much better tolerated and preferred for diagnosing Dry Eye Syndrome.

Q: Marginal catarrhal corneal ulcer is caused by which of the following?

All of the above. **Explanation:** **Marginal catarrhal corneal ulcer** (also known as a marginal keratitis) is not a direct infection of the cornea, but rather a **Type III hypersensitivity reaction** (antigen-antibody complex mediated) to bacterial exotoxins. **Why "All of the above" is correct:** The condition is most commonly associated with chronic blepharitis. The bacterial antigens from the lid margins trigger an immune response where complexes deposit in the peripheral cornea. While **Staphylococcus aureus** is the most frequent culprit, other organisms known to cause chronic blepharitis and subsequent marginal ulcers include **Moraxella lacunata** and **Haemophilus aegyptius**. Therefore, all three organisms listed are recognized etiological agents. **Clinical Mechanism:** The "lucid interval" (a clear space between the ulcer and the limbus) is a hallmark of this condition. This occurs because the high molecular weight antibodies (IgM) cannot easily diffuse to the extreme periphery, and the limbal blood vessels provide a constant supply of fresh complement and inflammatory cells that localize the reaction slightly away from the limbus. **High-Yield Clinical Pearls for NEET-PG:** * **Nature of Ulcer:** It is a sterile, "cold" ulcer (non-infectious). * **Key Feature:** Presence of a **clear zone (lucid interval)** between the limbus and the ulcer. * **Symptoms:** Mild irritation, photophobia, and lacrimation (less severe than bacterial keratitis). * **Treatment:** Unlike infectious ulcers, these respond rapidly to **topical steroids** combined with antibiotic coverage for the underlying blepharitis. * **Differential Diagnosis:** Must be distinguished from Mooren’s ulcer (which is idiopathic, painful, and lacks a lucid interval).

Q: The central nebular corneal opacity is best treated with which procedure?

Lamellar keratoplasty. ### Explanation **Correct Option: A. Lamellar Keratoplasty** The management of corneal opacities depends on the **depth** and **density** of the scar. A **nebular opacity** is a faint, superficial scar that involves only the epithelium and the superficial layers of the stroma. In **Lamellar Keratoplasty (LKP)**, only the diseased superficial layers of the cornea are removed and replaced with donor tissue, leaving the healthy host endothelium intact. Since a nebular opacity does not involve the deep stroma or endothelium, LKP is the treatment of choice as it carries a lower risk of graft rejection and shorter recovery time compared to full-thickness procedures. **Analysis of Incorrect Options:** * **B. Penetrating Keratoplasty (PKP):** This is a full-thickness transplant. While it would remove the opacity, it is unnecessarily invasive for a superficial scar. PKP is reserved for **macular or leucomatous opacities** that involve the full thickness of the stroma. * **C & D. Contact Lenses:** Nebular opacities cause significant visual impairment due to **irregular astigmatism** and light scattering (diffraction). While RGP lenses (Option C) can correct irregular astigmatism, they do not eliminate the light scattering caused by the opacity itself. Therefore, surgical removal is required for definitive treatment. **High-Yield Clinical Pearls for NEET-PG:** * **Grading of Opacities:** 1. **Nebula:** Faint, iris details clearly visible. 2. **Macula:** Translucent, iris details seen indistinctly. 3. **Leucoma:** Opaque/White, iris details not visible. * **PTK (Phototherapeutic Keratectomy):** If the nebular opacity is very superficial (Bowman’s layer/superficial stroma), Excimer laser PTK is an alternative modern treatment. * **Deep Anterior Lamellar Keratoplasty (DALK):** The preferred modern variant of LKP for opacities involving up to the pre-Descemet's layer.

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)**.

Question 1

Which of the following is NOT true regarding the treatment of bacterial corneal ulcer?

Accepted Answer

Steroids are usually given in persistent epithelial defects

Answer

Fortified antibiotic eye drops

Answer

Cycloplegic and mydriatic agents to relieve pain

Answer

Cyanoacrylate glue is indicated in the treatment of small perforations

Question 2

Keratomalacia includes the following except?

Accepted Answer

Severe pain in the eye

Answer

Night blindness

Answer

Xerosis of the cornea

Answer

Perforation of cornea

Question 3

Keratomalacia is a clinical manifestation associated with which of the following conditions?

Accepted Answer

Diarrheal diseases

Answer

Varicella infection

Answer

Mumps

Answer

All of the above

Question 4

In Keratoconus, all are seen except?

Accepted Answer

Hypermetropic refractive error

Answer

Munson's sign

Answer

Thinning of cornea in the center

Answer

Distortion of corneal reflex at the center

Question 5

What is the diagnostic test for a corneal ulcer?

Accepted Answer

Sodium fluorescein dye

Answer

Methylene blue

Answer

Alcian blue

Answer

Rose Bengal

Question 6

Marginal catarrhal corneal ulcer is caused by which of the following?

Accepted Answer

All of the above

Answer

Staphylococcus

Answer

Moraxella

Answer

Haemophilus

Question 7

The central nebular corneal opacity is best treated with which procedure?

Accepted Answer

Lamellar keratoplasty

Answer

Penetrating keratoplasty

Answer

Gas permeable contact lens

Answer

Soft contact lens

Question 8

Irido-Corneal Endothelial syndrome is characterized by?

Accepted Answer

Deposition of abnormal collagen in Descemet's membrane

Answer

Opacity of the cornea with edema of the stroma

Answer

Deposition of glycosaminoglycans in Descemet's membrane

Answer

Diffuse bilateral senile iris degeneration

Question 9

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 10

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

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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