Diseases of the Cornea Practice Questions

Q: Important in Herpes simplex involvement of the eye are all EXCEPT:

Purulent discharge. **Explanation:** Herpes Simplex Virus (HSV) keratitis is a leading cause of corneal blindness. The correct answer is **Purulent discharge**, as this is a hallmark of **bacterial conjunctivitis/keratitis**, not viral infections. Viral infections typically present with watery (serous) discharge. **Why the other options are characteristic of HSV:** * **Type of lesion (Option A):** HSV is famous for its specific morphological patterns. The most common is the **dendritic ulcer** (linear, branching with terminal bulbs), which stains with Fluorescein. If treated with steroids, it can enlarge into a **geographic ulcer**. * **Corneal anaesthesia (Option B):** HSV is a neurotropic virus that resides in the trigeminal ganglion. Its replication leads to the destruction of corneal nerve endings, resulting in **marked corneal hypoesthesia or anesthesia**. This is a classic diagnostic sign. * **Iridocyclitis (Option C):** HSV can cause secondary anterior uveitis (iridocyclitis) either through direct viral invasion or an immunologic reaction. It is often associated with high intraocular pressure (hypertensive uveitis). **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** The floor of the dendritic ulcer stains with **Fluorescein**, while the virus-laden cells at the margins (terminal bulbs) stain with **Rose Bengal**. * **Treatment:** Topical **Acyclovir (3%)** or Ganciclovir gel is the gold standard. **Steroids are strictly contraindicated** in epithelial (dendritic) keratitis as they promote viral replication, leading to geographic ulcers. * **Recurrence:** HSV remains latent in the **Trigeminal (V) ganglion**. * **Disciform Keratitis:** This is a type of stromal involvement characterized by a central, disc-shaped area of corneal edema, thought to be a Type IV hypersensitivity reaction.

Q: A 20-year-old male presents with sudden onset left eye pain and vision loss. Examination reveals a hazy left cornea. Upon looking down, a bulge is noted in the lower eyelid. Retinoscopy demonstrates a scissoring reflex and a positive oil drop sign in both eyes. What is the diagnosis?

Keratoconus. **Explanation:** The clinical presentation is a classic case of **Keratoconus**, a non-inflammatory, progressive thinning and ectasia of the central or paracentral cornea. **Why Keratoconus is correct:** * **Munson’s Sign:** The "bulge in the lower eyelid upon looking down" is a pathognomonic sign caused by the cone-shaped cornea indenting the lid. * **Oil Drop Sign:** Seen on distant direct ophthalmoscopy, this represents the conical protrusion. * **Scissoring Reflex:** Observed during retinoscopy due to irregular astigmatism. * **Acute Hydrops:** The "sudden onset pain and vision loss with a hazy cornea" indicates a rupture in **Descemet’s membrane**, leading to stromal edema (Acute Hydrops), a known complication of keratoconus. **Why other options are incorrect:** * **Corneal Dystrophy:** These are typically bilateral, symmetrical, and slowly progressive without the specific conical bulging or Munson’s sign. * **Pathological Myopia:** While it causes vision loss and high refractive error, it involves posterior segment changes (e.g., Fuchs' spot, staphyloma) rather than corneal ectasia or Munson's sign. * **Keratoglobus:** This involves hemispherical protrusion and thinning of the *entire* cornea from limbus to limbus, rather than a localized cone. It rarely presents with acute hydrops. **High-Yield Clinical Pearls for NEET-PG:** * **Fleischer’s Ring:** Iron deposition at the base of the cone (best seen with Cobalt blue filter). * **Vogt’s Striae:** Vertical stress lines in the deep stroma. * **Rizutti’s Sign:** Conical reflection on the nasal cornea when light is shone from the temporal side. * **Management:** Early stages use spectacles/RGP lenses; **Collagen Cross-linking (CXL/C3R)** stops progression; Keratoplasty is for advanced cases. *Note: Steroids are contraindicated in acute hydrops.*

Q: Posterior polymorphous dystrophy is characterized by which of the following?

Corectopia. **Explanation:** **Posterior Polymorphous Dystrophy (PPMD)** is a rare, usually autosomal dominant, bilateral corneal dystrophy affecting the corneal endothelium and Descemet membrane. **Why Corectopia is Correct:** The hallmark of PPMD is the transformation of corneal endothelial cells into "epithelial-like" cells. These abnormal cells have a migratory property; they can grow across the trabecular meshwork and onto the surface of the iris. As these membranes contract, they pull the iris, leading to **corectopia** (displacement of the pupil), ectropion uveae, and peripheral anterior synechiae (PAS). This mechanism is similar to that seen in Iridocorneal Endothelial (ICE) syndrome. **Analysis of Incorrect Options:** * **B. Autosomal recessive inheritance:** PPMD is typically inherited in an **Autosomal Dominant** pattern (linked to mutations in *ZEB1*, *COL8A2*, or *OVOL2* genes). * **C. Blindness in over 90% of sufferers:** Most patients are asymptomatic and the condition is often stable. Only a small percentage develop significant corneal edema or secondary glaucoma leading to severe vision loss. * **D. Treatment with lamellar corneal grafts:** While severe cases require surgery, the standard is **Penetrating Keratoplasty (PK)** or **Endothelial Keratoplasty (DSEK/DMEK)**. Simple lamellar grafts (which replace only the stroma) do not address the underlying endothelial pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Vesicular lesions:** Characterized by "railroad track" or "snail track" opacities on the posterior cornea. * **Glaucoma:** Occurs in ~15% of cases due to membrane overgrowth in the angle. * **Differential Diagnosis:** Must be distinguished from **ICE Syndrome** (which is unilateral and non-hereditary) and **CHED** (Congenital Hereditary Endothelial Dystrophy).

Q: Which of the following is NOT an indication for the prosthesis shown in the image?

Oral Contraceptive Pills (OCP) - Stage 1 or 2. ***Oral Contraceptive Pills (OCP) - Stage 1 or 2*** - **Early-stage OCP** (Stage I-II by Foster/Mondino staging) does NOT qualify for **Boston Keratoprosthesis** as the corneal surface is still manageable with medical therapy. - **Boston KPro** is reserved for **advanced stages (III-IV)** with severe **dry eye**, **surface keratinization**, and failed conventional treatments. *Crouzon Disease* - **Syndromic craniosynostosis** with **shallow orbits** leads to severe **exposure keratopathy** and corneal scarring unresponsive to conventional grafts. - The **anatomical abnormalities** make traditional **penetrating keratoplasty** technically challenging and prone to failure. *Multiple failed Penetrating Keratoplasty* - **Repeated PKP failures** indicate poor **host bed vascularity** or **immune-mediated rejection**, making further conventional grafts futile. - **Boston KPro** bypasses the need for **donor corneal tissue integration** and provides immediate visual rehabilitation. *Epidermolysis Bullosa Acquisita* - **Autoimmune blistering disease** causes severe **cicatricial changes** and **symblepharon formation** that destroy the corneal surface. - The **chronic inflammatory process** makes conventional grafts prone to failure due to poor healing and recurrent scarring.

Q: What is the most common cause of corneal keratitis in soft contact lens users?

Pseudomonas keratitis. **Explanation:** **Pseudomonas keratitis** is the most common cause of bacterial keratitis in soft contact lens wearers. The underlying medical concept involves the ability of *Pseudomonas aeruginosa* to adhere to the surface of soft contact lenses (especially hydrogel and silicone hydrogel types) and the lens cases. It produces proteases and toxins that can cause rapid stromal necrosis and corneal perforation, often presenting as a characteristic "soupy" yellowish-green discharge. **Analysis of Options:** * **Acanthamoeba keratitis:** While highly associated with poor contact lens hygiene (e.g., using tap water), it is much **rarer** than bacterial infections. It is characterized by "pain out of proportion to clinical findings" and ring-shaped infiltrates. * **Corneal erosion:** This is a mechanical complication or a sequela of trauma/dystrophy, not an infectious keratitis. While contact lenses can cause abrasions, they are not the primary "cause" of infectious keratitis itself. * **Herpes simplex keratitis:** This is typically a viral reactivation in the trigeminal ganglion and is not specifically linked to contact lens use. It presents with characteristic dendritic ulcers. **High-Yield Clinical Pearls for NEET-PG:** * **Most common organism overall for bacterial keratitis:** *Staphylococcus aureus*. * **Most common organism in contact lens users:** *Pseudomonas aeruginosa*. * **Risk Factors:** Overnight wear (extended wear) is the single greatest risk factor for developing contact lens-related keratitis. * **Clinical Sign:** Look for a rapidly progressing ulcer with a ground-glass appearance of the surrounding cornea. * **Management:** Immediate cessation of lens wear and intensive topical fortified antibiotics (e.g., Fluoroquinolones or Cephazolin + Gentamicin).

Q: Under hypoxic conditions, which of the following is strongly implicated as a cause of corneal edema?

Lactate. **Explanation:** The cornea maintains its transparency through a state of relative dehydration (deturgescence). This balance is primarily managed by the corneal endothelium's metabolic pump. **Why Lactate is Correct:** Under **hypoxic conditions** (commonly caused by contact lens overwear or epithelial edema), the cornea shifts from aerobic metabolism to **anaerobic glycolysis**. In this pathway, glucose is converted into **lactate** instead of entering the Krebs cycle. Because the corneal epithelium is relatively impermeable to lactate, it accumulates within the corneal stroma. This creates an **osmotic gradient** that draws water from the aqueous humor into the stroma, resulting in **corneal edema**. **Analysis of Incorrect Options:** * **B. Glycogen:** This is the storage form of glucose in the corneal epithelium. During hypoxia, glycogen stores are depleted (not increased) to provide glucose for anaerobic metabolism. * **C. Carbon dioxide:** While CO2 levels may rise slightly during hypoxia, it diffuses rapidly out of the cornea and does not exert the significant osmotic pressure required to cause stromal edema. * **D. Pyruvate:** In the anaerobic pathway, pyruvate is rapidly converted into lactate by the enzyme lactate dehydrogenase (LDH). It is the accumulation of the end-product (lactate), not the intermediate (pyruvate), that drives the osmotic shift. **High-Yield Clinical Pearls for NEET-PG:** * **Maurice’s Theory:** Attributes corneal transparency to the uniform lattice arrangement of collagen fibrils. * **Goldmann’s Theory:** Attributes transparency to the small size of fibrils (less than half the wavelength of light). * **Critical Oxygen Tension:** The minimum oxygen required to prevent corneal edema is approximately **11–19 mmHg**. * **Pachymetry:** The gold standard for measuring corneal thickness; an increase in thickness is the earliest clinical sign of corneal edema.

Q: Which of the following medications is NOT typically administered as eye drops for a corneal ulcer?

Flurometholone. **Explanation:** The management of a corneal ulcer (keratitis) focuses on treating the underlying infection and promoting epithelial healing. **Fluorometholone** is a topical corticosteroid. In the acute phase of a corneal ulcer, steroids are generally **contraindicated** because they inhibit collagen synthesis and suppress the local immune response. This can lead to the worsening of the infection, delayed wound healing, and even corneal perforation (melting). Steroids are only considered in specific bacterial cases once the infection is controlled, to reduce scarring. **Analysis of Options:** * **Chloramphenicol (Option A):** A broad-spectrum bacteriostatic antibiotic frequently used as first-line prophylaxis or treatment for bacterial corneal ulcers. * **Methylcellulose (Option B):** A lubricating agent (artificial tears) used to maintain ocular surface integrity and promote re-epithelialization by reducing friction. * **Olopatadine (Option C):** An antihistamine/mast cell stabilizer. While primarily for allergic conjunctivitis, it is not contraindicated in an ulcer and does not impede healing like steroids do. **Clinical Pearls for NEET-PG:** * **Steroid Contraindication:** Never use steroids in a dendritic ulcer (Herpes Simplex Keratitis) as it leads to a "Geographic ulcer." * **Fortified Antibiotics:** For severe bacterial ulcers, "fortified" drops (e.g., Cefazolin 5% or Tobramycin 1.4%) are preferred over standard strengths. * **Atropine (1%):** Often added to the regimen to relieve ciliary spasm (pain) and prevent posterior synechiae formation. * **Natamycin (5%):** The drug of choice for filamentous fungal corneal ulcers.

Q: KISA% is associated with which of the following conditions?

Keratoconus. **Explanation:** **KISA%** is a quantitative screening index used for the diagnosis and classification of **Keratoconus**. It was developed by Rabinowitz and Rasheed to distinguish normal corneas from those with subclinical or clinical keratoconus using corneal topography data. The index is calculated using four specific parameters: 1. **K:** Central keratometry (K-value). 2. **I-S:** Inferior-Superior dioptric asymmetry. 3. **AST:** Degree of regular astigmatism. 4. **SRAX:** Skewed Radial Axis index. A **KISA% value >100** is considered diagnostic for Keratoconus, while values between 60–100 are suggestive of "suspect" or early disease. **Analysis of Incorrect Options:** * **B. Keratoglobus:** While it is an ectatic dystrophy, it involves generalized thinning and protrusion of the entire cornea (limbus to limbus), unlike the localized paracentral thinning seen in keratoconus where KISA% is specifically applied. * **C. Hypermetropia with astigmatism:** KISA% is a tool for corneal ectasia, not simple refractive errors. * **D. Terrien's marginal degeneration:** This is a peripheral corneal thinning condition characterized by "painless vascularized guttering," usually starting superiorly. It does not utilize the KISA% index for diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Munson’s Sign:** V-shaped indentation of the lower lid on down-gaze (late sign). * **Vogt’s Striae:** Vertical stress lines in the deep stroma/Descemet’s membrane. * **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. * **Treatment of choice for progression:** Collagen Cross-Linking (CXL/C3R).

Q: A patient presents to the eye outpatient department with disc-shaped edema over the cornea. The patient has a history of vesicles over the lips a few weeks prior. There is no ulceration upon staining. What is the most likely diagnosis?

Disciform viral keratitis. ### Explanation The clinical presentation of **disc-shaped corneal edema** (disciform keratitis) following a history of **vesicles over the lips** (suggestive of Herpes Simplex Virus - Labialis) is a classic description of **Disciform Viral Keratitis**. **1. Why Option A is Correct:** Disciform keratitis is a form of **endotheliitis** caused by a delayed-type hypersensitivity reaction (Type IV) to the Herpes Simplex Virus (HSV) antigen. Unlike epithelial keratitis, there is **no active viral replication** in the epithelium, which explains why there is **no ulceration** upon staining. The hallmark clinical sign is a central or paracentral zone of stromal edema with an intact epithelium, often accompanied by "keratic precipitates" (KPs) underlying the edema. **2. Why Other Options are Incorrect:** * **Option B (Marginal Ulcer):** These are typically hypersensitivity reactions to Staphylococcal exotoxins. They present as peripheral infiltrates with a clear space between the limbus and the ulcer, not as central disciform edema. * **Option C (Metaherpetic/Trophic Keratitis):** This is a mechanical failure of epithelial healing due to basement membrane damage and loss of corneal sensations (neurotrophic). It presents as a **non-healing ulcer** with smooth, rounded borders, which contradicts the "no ulceration" finding in this case. **Clinical Pearls for NEET-PG:** * **Gold Standard Treatment:** Topical steroids (to control the immune response) combined with prophylactic topical antivirals (to prevent viral reactivation). * **Wessely Ring:** An immune ring of stromal precipitation sometimes seen in disciform keratitis. * **Sensation:** Corneal sensations are typically **reduced** in HSV infections. * **Dendritic Ulcer:** The most common presentation of primary/recurrent epithelial HSV; it stains with Fluorescein (bed) and Rose Bengal (edges).

Question 1

Important in Herpes simplex involvement of the eye are all EXCEPT:

Accepted Answer

Purulent discharge

Answer

Type of lesion

Answer

Corneal anaesthesia

Answer

Iridocyclitis

Question 2

A 20-year-old male presents with sudden onset left eye pain and vision loss. Examination reveals a hazy left cornea. Upon looking down, a bulge is noted in the lower eyelid. Retinoscopy demonstrates a scissoring reflex and a positive oil drop sign in both eyes. What is the diagnosis?

Accepted Answer

Keratoconus

Answer

Corneal dystrophy

Answer

Pathological myopia

Answer

Keratoglobus

Question 3

Posterior polymorphous dystrophy is characterized by which of the following?

Accepted Answer

Corectopia

Answer

Autosomal recessive inheritance

Answer

Blindness in over 90% of sufferers

Answer

Treatment with lamellar corneal grafts

Question 4

Which of the following is NOT an indication for the prosthesis shown in the image?

Accepted Answer

Oral Contraceptive Pills (OCP) - Stage 1 or 2

Answer

Crouzon Disease

Answer

Multiple failed Penetrating Keratoplasty

Answer

Epidermolysis Bullosa Acquisita

Question 5

What is the most common cause of corneal keratitis in soft contact lens users?

Accepted Answer

Pseudomonas keratitis

Answer

Acanthamoeba keratitis

Answer

Corneal erosion

Answer

Herpes simplex keratitis

Question 6

Under hypoxic conditions, which of the following is strongly implicated as a cause of corneal edema?

Accepted Answer

Lactate

Answer

Glycogen

Answer

Carbon dioxide

Answer

Pyruvate

Question 7

Which of the following medications is NOT typically administered as eye drops for a corneal ulcer?

Accepted Answer

Flurometholone

Answer

Chloramphenicol

Answer

Methylcellulose

Answer

Olopatadine

Question 8

KISA% is associated with which of the following conditions?

Accepted Answer

Keratoconus

Answer

Keratoglobus

Answer

Hypermetropia with astigmatism

Answer

Terrien's marginal degeneration

Question 9

A patient presents to the eye outpatient department with disc-shaped edema over the cornea. The patient has a history of vesicles over the lips a few weeks prior. There is no ulceration upon staining. What is the most likely diagnosis?

Accepted Answer

Disciform viral keratitis

Answer

Marginal ulcer

Answer

Metherpetiform keratitis

Answer

None of the above

Question 10

Hypopyon ulcer may be produced by which of the following organisms?

Accepted Answer

All of the above

Answer

Pneumococcus

Answer

Pseudomonas

Answer

Gonococcus

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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