Diseases of the Cornea Practice Questions

Q: Best treatment for this corneal lesion is:

Topical acyclovir 3% with atropine. ***Topical acyclovir 3% with atropine*** - This regimen is the gold standard for treating **Herpes Simplex Keratitis**, specifically **dendritic ulcers**, to inhibit viral replication. - **Atropine** is added to prevent or manage secondary **uveitis** and provide pain relief by paralyzing the ciliary muscle. *Broad-spectrum topical antibiotics* - These are indicated for **bacterial keratitis**, presenting with dense **suppurative infiltrates** and mucopurulent discharge, not the characteristic dendritic pattern. - Using antibiotics for viral disease provides no therapeutic benefit and may cause ocular surface toxicity. *Topical steroids* - These are strictly **contraindicated** in active epithelial **Herpetic Keratitis** as they can cause rapid viral proliferation and **corneal melting**. - Steroids may only be considered under the coverage of antivirals for **stromal keratitis** (immune-mediated) or to manage severe **uveitis**, never for active epithelial disease. *Lubricating eye drops* - These are used for **dry eye syndrome** or mild surface irritation, which do not produce inflammatory corneal lesions. - They lack antimicrobial or antiviral properties and would be ineffective at treating an active **viral infection**.

Q: A young patient presents with this sign. Diagnosis is best made by:

Corneal topography. ***Corneal topography*** - This is the **gold standard** diagnostic tool for detecting early and subclinical forms of **keratoconus**, as it provides a detailed map of the corneal curvature. - It identifies characteristic patterns like **inferior steepening** and **asymmetric bowtie** appearance which precede clinical signs visible on slit-lamp examination. *Keratometry* - Keratometry measures the **corneal power** at two principal meridians but is unable to map the entire corneal surface. - It is generally insufficient for the early diagnosis of keratoconus as it only provides averaged readings of the **central cornea**. *Pachymetry* - While pachymetry measures **corneal thickness** and may show localized thinning, it is not a diagnostic tool for mapping the surface curvature. - It is an adjunctive test; thinning is a structural change, but topography provides the functional assessment of the **corneal shape** necessary for diagnosis. *A-scan* - A-scan ultrasonography is primarily used to measure the **axial length** of the eye, typically for **intraocular lens (IOL) power calculations**. - It offers no diagnostic utility in assessing the **topographical curvature** or surface irregularities characteristic of corneal ectasias.

Q: Corneal vascularization is caused by which of the following?

All of the above. **Explanation:** Corneal vascularization (neovascularization) is a pathological condition where new blood vessels grow into the normally avascular cornea. This occurs when the balance between angiogenic factors (like VEGF) and anti-angiogenic factors is disrupted, usually due to inflammation, hypoxia, or limbal stem cell deficiency. **Analysis of Options:** * **Graft Rejection (Option A):** This is an inflammatory immune response. Neovascularization is both a risk factor for and a sign of corneal graft rejection. Vessels provide a pathway for immune cells to reach the donor tissue, leading to an "immune attack." * **Chemical Burn (Option B):** Alkali burns are particularly notorious. They cause extensive limbal stem cell damage and severe inflammation. The loss of the limbal barrier allows conjunctival vessels to encroach upon the cornea (conjunctivalization). * **Contact Lens Use (Option C):** Chronic use, especially with low-permeability lenses or overwear, leads to **corneal hypoxia**. The lack of oxygen triggers the release of vasoproliferative factors, causing superficial or deep stromal vessels to grow from the limbus. Since all three conditions are well-established causes of corneal neovascularization, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** * **Pannus:** This refers to superficial vascularization accompanied by infiltration of granulation tissue (commonly seen in Trachoma and Phlyctenular keratoconjunctivitis). * **Micropannus:** Defined as vessel growth <2mm beyond the limbus (common in Trachoma). * **Ghost Vessels:** These are non-perfused, empty vascular channels that remain after the inciting inflammatory stimulus has subsided (classic in interstitial keratitis/Syphilis). * **Management:** Topical steroids or NSAIDs are used to reduce inflammation; anti-VEGF agents (e.g., Bevacizumab) are emerging treatments.

Q: In microcornea, the diameter of the cornea is less than:

10 mm. **Explanation:** **Microcornea** is a congenital anomaly where the cornea is abnormally small but otherwise anatomically normal in structure and thickness. 1. **Why Option B is correct:** The standard clinical definition of microcornea is a horizontal corneal diameter of **less than 10 mm** in an adult, or **less than 9 mm** in a newborn. Since the question refers to the general diagnostic threshold, 10 mm is the established benchmark. The condition occurs due to an arrest in the growth of the cornea after the 5th month of gestation, while the rest of the eye may grow normally. 2. **Why other options are incorrect:** * **Option A (9 mm):** This is the threshold for a **newborn**. In an adult, a 9 mm cornea is already well within the range of microcornea. * **Option C (11 mm):** The average adult corneal diameter is approximately 11.5 to 12 mm. A diameter of 11 mm is considered a "small-normal" cornea but does not meet the pathological criteria for microcornea. * **Option D (8 mm):** While an 8 mm cornea is indeed microcorneal, it is not the *threshold* definition. 10 mm is the upper limit for the diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Refractive Status:** Microcornea usually results in **hypermetropia** (flat cornea) and predisposes the patient to **closed-angle glaucoma** due to a crowded anterior segment. * **Associations:** It can occur in an otherwise normal eye (isolated) or as part of **Microphthalmos** (small globe). * **Systemic Associations:** Often linked with **Fetal Alcohol Syndrome**, Turner syndrome, and Ehlers-Danlos syndrome. * **Contrast with Megalocornea:** Megalocornea is defined as a horizontal diameter **>13 mm**.

Q: Which of the following is NOT a sign of graft rejection?

Foster spot. **Explanation:** The correct answer is **Foster spot** because it is a clinical feature of **Pathological Myopia**, not corneal graft rejection. A Foster-Fuchs spot is a pigmented, circular lesion in the macula caused by subretinal neovascularization and subsequent scarring/hemorrhage. **Understanding Graft Rejection Signs:** Corneal graft rejection is an immunological response (Type IV hypersensitivity) against the donor tissue. It can involve different layers of the cornea: * **Krachmer spots (Option A):** These are subepithelial infiltrates seen in **stromal rejection**. They represent a localized inflammatory response and are similar in appearance to the infiltrates seen in epidemic keratoconjunctivitis. * **Khodadoust line (Option B):** This is the hallmark sign of **endothelial rejection**. It is a linear precipitate of lymphocytes (keratic precipitates) on the endothelium that moves across the graft, destroying endothelial cells and leading to graft failure. * **Oedema (Option C):** Corneal edema (thickening and loss of clarity) is a primary sign of **endothelial rejection**. When the pump function of the endothelium is compromised by the immune attack, the stroma becomes hydrated. **High-Yield Clinical Pearls for NEET-PG:** * **Wessely Ring:** An immune ring in the corneal stroma (antigen-antibody complex) often seen in viral keratitis or graft rejection. * **Timeframe:** Graft rejection typically occurs at least 2 weeks after surgery (sensitization period). * **Management:** The mainstay of treatment is intensive **topical corticosteroids** (e.g., Prednisolone acetate 1%). * **Epithelial Rejection:** Characterized by an elevated epithelial line (rejection line) that stains with fluorescein.

Q: Corneal endothelial cell counting is performed using which instrument?

Specular microscope. ### Explanation **Correct Answer: C. Specular microscope** The **corneal endothelium** is a single layer of non-regenerating hexagonal cells responsible for maintaining corneal dehydration (deturgescence) via an active Na+/K+ ATPase pump. **Specular microscopy** is a non-invasive photographic technique that allows for the visualization and analysis of these cells. It provides critical data including: * **Endothelial Cell Density (ECD):** Normal adult count is 2000–3000 cells/mm². * **Polymegathism:** Variation in cell size (Coefficient of Variation). * **Pleomorphism:** Variation in cell shape (Percentage of hexagonality). **Analysis of Incorrect Options:** * **A. Tachymetry:** This is a distractor term. In general engineering, it refers to distance measurement, but it has no standard application in clinical ophthalmology. * **B. Pachymetry:** This instrument measures **corneal thickness**. While thickness is an indirect indicator of endothelial function (as a failing pump leads to edema/thickening), it does not count individual cells. * **D. Perimetry:** This is used for mapping the **visual field** (e.g., Humphrey Field Analyzer), primarily used in the diagnosis and management of glaucoma and neurological visual defects. **High-Yield Clinical Pearls for NEET-PG:** * **Critical Threshold:** If the endothelial cell count falls below **500 cells/mm²**, the cornea loses its ability to remain clear, leading to corneal edema and bullous keratopathy. * **Guttata:** Specular microscopy shows these as "dark spots" or "holes" in the endothelial pattern, characteristic of **Fuchs' Endothelial Dystrophy**. * **Surgical Clearance:** Specular microscopy is mandatory before certain procedures like ICL (Implantable Collamer Lens) implantation to ensure the endothelium is healthy enough to tolerate the intraocular surgery.

Q: Filamentary keratitis may occur:

All of the above. **Explanation:** Filamentary keratitis is a chronic condition characterized by the formation of small, mucoid filaments attached to the corneal epithelium. These filaments consist of a core of mucus wrapped in degenerated epithelial cells. The underlying pathophysiology involves an **altered mucus-to-tear ratio** and focal areas of epithelial instability. **Why "All of the Above" is Correct:** 1. **Keratoconjunctivitis Sicca (KCS):** This is the most common cause. In dry eye states, the lack of aqueous tears leads to increased mucus viscosity. The friction between the lid and the dry corneal surface causes epithelial "tags" to which mucus adheres, forming filaments. 2. **Trachoma:** Chronic cicatricial changes in trachoma lead to secondary dry eye (due to destruction of goblet cells and lacrimal ducts) and mechanical irritation from entropion or trichiasis, both of which predispose the cornea to filament formation. 3. **Following Cataract Surgery:** Post-operative filamentary keratitis can occur due to prolonged patching, use of topical NSAIDs, or surgical trauma to the corneal nerves, which decreases corneal sensitivity and disrupts the tear film stability. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Feature:** Patients complain of a "foreign body sensation" that worsens with blinking (as the lid pulls on the filaments). * **Staining:** Filaments stain brilliantly with **Rose Bengal** (which stains mucus and devitalized cells). * **Associated Conditions:** Also seen in Superior Limbic Keratoconjunctivitis (SLK), Sjögren’s syndrome, and prolonged eye patching (Ptosis surgery). * **Treatment:** Management includes mechanical removal of filaments, use of **mucolytic agents (Acetylcysteine 10%)**, and aggressive lubrication.

Question 1

Best treatment for this corneal lesion is:

Accepted Answer

Topical acyclovir 3% with atropine

Answer

Broad-spectrum topical antibiotics

Answer

Topical steroids

Answer

Lubricating eye drops

Question 2

A young patient presents with this sign. Diagnosis is best made by:

Accepted Answer

Corneal topography

Answer

Keratometry

Answer

Pachymetry

Answer

A-scan

Question 3

Corneal vascularization is caused by which of the following?

Accepted Answer

All of the above

Answer

Graft rejection

Answer

Chemical burn

Answer

Contact lens use

Question 4

In microcornea, the diameter of the cornea is less than:

Accepted Answer

10 mm

Answer

9 mm

Answer

11 mm

Answer

8 mm

Question 5

Which of the following is NOT a sign of graft rejection?

Accepted Answer

Foster spot

Answer

Krachmer spots

Answer

Khodadoust line

Answer

Oedema

Question 6

Corneal endothelial cell counting is performed using which instrument?

Accepted Answer

Specular microscope

Answer

Tachymetry

Answer

Pachymetry

Answer

Perimetry

Question 7

Filamentary keratitis may occur:

Accepted Answer

All of the above

Answer

In trachoma

Answer

In kerato conjunctivitis sicca

Answer

Following cataract surgery

Question 8

Which of the following is a common fungus causing corneal ulcer?

Accepted Answer

Sporothrix

Answer

Aspergillus

Answer

Mucor

Answer

Fusarium

Question 9

Which of the following organisms can penetrate the normal cornea?

Accepted Answer

Staphylococcus epidermidis

Answer

Gonococcus

Answer

Pseudomonas

Answer

Diphtheria

Question 10

All of the following are true about corneal endothelium except?

Accepted Answer

Corneal decompensation occurs when cell count is decreased by 50 percent.

Answer

Cell density is about 3000 cells/mm² at birth.

Answer

Endothelial cells contain an active pump mechanism.

Answer

Endothelium is best examined by specular microscopy.

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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