Diseases of the Cornea Practice Questions

Q: Neuroparalytic keratitis is most commonly associated with damage to which cranial nerve?

Trigeminal nerve (CN V). **Explanation:** **Neuroparalytic keratitis** (also known as neurotrophic keratopathy) occurs due to the loss of sensory innervation to the cornea. The **Trigeminal nerve (CN V)**, specifically its ophthalmic division (V1) via the long ciliary nerves, provides this sensory supply. When CN V is damaged, the cornea loses its protective sensations and trophic factors. This leads to a decrease in the blink reflex, reduced tear film stability, and impaired epithelial healing, ultimately resulting in persistent epithelial defects and corneal ulceration. **Analysis of Incorrect Options:** * **Oculomotor nerve (CN III):** Damage leads to ptosis and extraocular muscle palsy. While a drooping eyelid might actually protect the cornea (pseudoptosis), it does not cause neuroparalytic keratitis. * **Abducens nerve (CN VI):** This nerve supplies the lateral rectus muscle. Damage causes esotropia (inward deviation) and diplopia, but has no effect on corneal sensation or integrity. * **Facial nerve (CN VII):** Damage to CN VII leads to **Exposure Keratitis**. This is due to the paralysis of the orbicularis oculi muscle, resulting in lagophthalmos (inability to close the eye), which causes the cornea to dry out. It is a motor deficit, whereas neuroparalytic keratitis is a sensory deficit. **High-Yield Clinical Pearls for NEET-PG:** * **Key Distinction:** Remember **"S"** for **S**ensory/Trigeminal = Neuro**p**aralytic; **"M"** for **M**otor/Facial = **E**xposure Keratitis. * **Common Causes:** CN V damage can occur due to Herpes Zoster Ophthalmicus, acoustic neuroma (at the cerebellopontine angle), or surgical trauma during trigeminal neuralgia procedures. * **Clinical Feature:** A hallmark of neuroparalytic keratitis is a **painless** corneal ulcer with characteristic rolled-up epithelial edges.

Q: Corneal ulcer can lead to which of the following complications?

Anterior staphyloma. **Explanation:** A corneal ulcer, particularly if it progresses to perforation, can lead to the formation of an **Anterior Staphyloma**. When a corneal ulcer causes a large perforation, the iris prolapses through the defect. Over time, this prolapsed iris becomes covered by a thin layer of fibro-cicatricial tissue (pseudocornea). Due to the weakness of this new tissue and the associated rise in intraocular pressure (secondary glaucoma), the area bulges forward, resulting in a slate-colored protrusion known as an anterior staphyloma. **Analysis of Incorrect Options:** * **Posterior Staphyloma:** This is a protrusion of the weakened sclera lined by uveal tissue at the posterior pole of the eye. It is a hallmark of **Pathological Myopia**, not corneal ulceration. * **Lenticonus:** This is a congenital localized cone-shaped protrusion of the anterior or posterior lens surface. Anterior lenticonus is classically associated with **Alport Syndrome**. * **Keratoconus:** This is a non-inflammatory, progressive thinning and ectasia of the central or paracentral cornea. While it involves corneal bulging, it is a degenerative condition and not a direct complication of an acute infectious corneal ulcer. **High-Yield Clinical Pearls for NEET-PG:** * **Descemetocele:** This occurs when a corneal ulcer erodes everything except Descemet’s membrane; it appears as a transparent, bulging vesicle and is a precursor to perforation. * **Secondary Glaucoma:** This is the most common cause of the "bulge" in an anterior staphyloma. * **Management:** A small perforation is managed with Cyanoacrylate glue, while a large perforation requires a tectonic keratoplasty.

Q: Neuroparalytic keratitis is associated with paralysis of which cranial nerve?

7th cranial nerve. **Explanation:** **Neuroparalytic keratitis** (also known as exposure keratitis) occurs due to the paralysis of the **7th cranial nerve (Facial nerve)**. The facial nerve supplies the **orbicularis oculi** muscle, which is responsible for eyelid closure. When this nerve is paralyzed (as seen in Bell’s palsy or acoustic neuroma surgery), the patient develops **lagophthalmos**—the inability to close the eyelids. This leads to constant exposure of the cornea, causing drying of the tear film, epithelial desiccation, and subsequent ulceration. **Analysis of Incorrect Options:** * **3rd Cranial Nerve (Oculomotor):** Paralysis causes **ptosis** (drooping of the eyelid). Because the eye remains covered by the lid, the cornea is actually protected from exposure. * **4th (Trochlear) & 6th (Abducens) Cranial Nerves:** These nerves supply extraocular muscles (Superior Oblique and Lateral Rectus, respectively). Paralysis leads to diplopia and squint but does not affect eyelid closure or corneal integrity. **Clinical Pearls for NEET-PG:** 1. **Neuroparalytic vs. Neurotrophic Keratitis:** Do not confuse the two. * **Neuroparalytic (7th Nerve):** Motor loss leading to exposure. * **Neurotrophic (5th Nerve/Trigeminal):** Sensory loss leading to loss of corneal reflex and poor epithelial healing. 2. **Bell’s Phenomenon:** This is the upward and outward rolling of the eyeball during attempted lid closure. It acts as a protective mechanism in 7th nerve palsy. 3. **Management:** Initial treatment involves frequent lubricants and taping the lids at night. For permanent palsy, **Tarsorrhaphy** (suturing the lids together) is the definitive surgical treatment.

Q: All of the following are signs of mycotic corneal ulcer, EXCEPT:

Corneal vascularization. **Explanation:** The hallmark of a **mycotic (fungal) corneal ulcer** is its indolent nature and the relative absence of early vascularization. Unlike bacterial ulcers, which often trigger an acute inflammatory response leading to rapid neovascularization, fungal ulcers are characterized by **lack of corneal vascularization**. The fungi produce toxins and enzymes that suppress the host's early angiogenic response, making the ulcer appear "dry" and gray. **Analysis of Options:** * **Corneal vascularization (Correct Answer):** This is typically absent in fungal keratitis. Its presence usually suggests a bacterial etiology, a healing stage, or a chronic viral infection (like HSV). * **Large hypopyon:** Fungal ulcers often present with a massive, thick, and non-sterile hypopyon. It is frequently "immobile" due to its high fibrin content and may even be present when the ulcer is relatively small. * **Sterile immune ring (Wessely ring):** This is a classic sign of fungal keratitis, representing a host antigen-antibody reaction (Type III hypersensitivity) where fungal antigens meet host antibodies in the stroma. * **Feathery, finger-like extensions:** These are characteristic "satellite lesions" or hyphal extensions that project from the main ulcer into the surrounding stroma, reflecting the infiltrative growth pattern of filamentous fungi (e.g., *Aspergillus*, *Fusarium*). **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause:** *Aspergillus* (overall), but *Fusarium* is common in trauma with vegetative matter (e.g., a branch hitting the eye). * **Key Signs:** Dry, leathery appearance, raised margins, satellite lesions, and a "fixed" hypopyon. * **Diagnosis:** KOH mount (shows hyphae) and Sabouraud’s Dextrose Agar (SDA). * **Treatment:** Topical Natamycin (5%) is the drug of choice for filamentous fungi.

Q: Which of the following does not cause cornea verticillata?

Tay-Sachs disease. **Explanation:** **Cornea Verticillata** (also known as vortex keratopathy) is characterized by bilateral, symmetrical, golden-brown or greyish-white whorl-like opacities in the basal epithelium of the cornea. **Why Tay-Sachs disease is the correct answer:** Tay-Sachs disease is a lysosomal storage disorder (deficiency of Hexosaminidase A) characterized by a **cherry-red spot** at the macula due to ganglioside accumulation in retinal ganglion cells. It does **not** involve the corneal epithelium and therefore does not cause cornea verticillata. **Analysis of incorrect options:** * **Fabry Disease:** This is the most common systemic disease associated with cornea verticillata. It is an X-linked lysosomal storage disorder (alpha-galactosidase A deficiency) where glycolipids deposit in the corneal epithelium. * **Amiodarone & Chloroquine/Hydroxychloroquine:** These are the most common pharmacological causes. The drugs (or their metabolites) bind to lipids within the lysosomes of the corneal epithelium. * **Indomethacin:** Though less common than Amiodarone, Indomethacin is a well-documented cause of whorl-like corneal deposits. **NEET-PG High-Yield Pearls:** * **Mnemonic for Cornea Verticillata (CHAI-T):** **C**hloroquine, **H**ydroxychloroquine, **A**miodarone (most common), **I**ndomethacin, **T**amoxifen. * **Fabry Disease:** Cornea verticillata is often the first clinical sign and is present in almost all affected males and many female carriers. * **Clinical Significance:** Most drug-induced vortex keratopathies are asymptomatic and do not require drug discontinuation, as they rarely affect visual acuity. * **Differential for Cherry-red spot:** Tay-Sachs, Central Retinal Artery Occlusion (CRAO), Niemann-Pick disease, and Gaucher disease.

Q: What is Dellen?

Localized thinning of the peripheral cornea. **Explanation:** **Dellen** (Fuchs’ Dellen) refers to a localized, saucer-shaped thinning of the peripheral cornea. It occurs due to **tear film instability** and localized dehydration of the corneal stroma. 1. **Why Option A is Correct:** The underlying mechanism is **focal stromal dehydration**. When there is an adjacent elevation (like a pterygium, chemosis, or a large subconjunctival hemorrhage), the eyelid is "tented" up, preventing the tear film from wetting the adjacent corneal surface. This leads to rapid evaporation and secondary thinning of the stroma. On examination, it appears as a dry, depressed area with clear margins. 2. **Why Other Options are Incorrect:** * **Option B:** Raised lesions at the corneoscleral junction are characteristic of conditions like **Phlyctenular keratoconjunctivitis** or Limbal Dermoids, whereas Dellen is a depression/thinning. * **Option C:** **Age-related macular degeneration (ARMD)** is a posterior segment disease affecting the retina, unrelated to corneal thinning. * **Option D:** **Marginal keratitis** is an inflammatory/hypersensitivity reaction to Staphylococcal exotoxins, characterized by infiltrates and ulcers, not simple dehydration-induced thinning. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogenesis:** Discontinuity of the precorneal tear film (not an inflammatory process). * **Clinical Feature:** A "saucer-like" depression near the limbus. Fluorescein pools in the depression but does not necessarily stain it (unless the epithelium is breached). * **Treatment:** Frequent application of artificial tears and lubricants; occasionally patching to rehydrate the stroma. * **Prognosis:** Usually reversible once the adjacent elevation is removed or the area is rehydrated.

Q: What is the most common cause of anterior staphyloma?

Corneal Ulcer. **Explanation:** **Anterior staphyloma** is a condition characterized by a bulging, ectatic cicatrix (scar tissue) formed by the incorporation of the iris into a thinned, perforated cornea. **Why Corneal Ulcer is the correct answer:** The most common underlying cause is a **perforating corneal ulcer** (often due to bacterial or fungal infections). When a central corneal ulcer perforates, the iris prolapses forward to plug the defect. Over time, the iris becomes covered by a thin layer of fibrous tissue and epithelium (pseudocornea). Because this newly formed tissue is weaker than the original cornea and cannot withstand normal intraocular pressure (IOP), it stretches and bulges forward, resulting in a dark, lobulated protrusion. **Why the other options are incorrect:** * **Herpes Keratitis:** While it can cause corneal scarring or thinning, it rarely leads to the massive perforation and iris incorporation required to form a staphyloma unless there is secondary bacterial superinfection or severe necrotizing keratitis. * **Myopia:** High myopia is associated with **posterior staphyloma** (bulging of the sclera at the posterior pole), not anterior staphyloma. * **Hypermetropia:** This is a refractive error associated with a shorter axial length and is not a cause of ectatic corneal diseases. **High-Yield Clinical Pearls for NEET-PG:** * **Appearance:** The staphyloma appears bluish-black because the pigmented iris tissue is visible through the thin, stretched pseudocornea. * **Vision:** Vision is typically reduced to "Projection of Rays" (PR) or "Hand Movements" (HM) due to total corneal opacity. * **Management:** For a blind, disfigured eye, the treatment of choice is **Evisceration** or **Staphylectomy**. * **Distinction:** Do not confuse this with **Keratectasia**, which is a protrusion of the cornea without iris involvement.

Q: Which part of the cornea is most affected in neuroparalytic keratopathy?

Inferior third of the cornea. **Explanation:** **Neuroparalytic keratopathy** (also known as neurotrophic keratitis) occurs due to the loss of sensory innervation to the cornea, specifically involving the **ophthalmic division (V1) of the Trigeminal nerve**. **Why the Inferior Third is Correct:** The sensory nerves of the cornea do more than just provide sensation; they release trophic factors (like Substance P and Nerve Growth Factor) essential for maintaining the health of the corneal epithelium. When these nerves are damaged, the corneal epithelium becomes friable and prone to desquamation. In neuroparalytic keratopathy, the **inferior third of the cornea** is most affected because this area is most exposed to environmental stress and minor trauma, and it is the region where the tear film is often thinnest or most unstable in the presence of reduced corneal sensitivity. **Analysis of Incorrect Options:** * **Superior third of the cornea:** This area is generally protected by the upper eyelid, which provides a constant moisture shield and reduces mechanical friction. * **Temporal third of the cornea:** While peripheral, it does not face the same degree of exposure or gravity-dependent drying as the inferior segment. **Clinical Pearls for NEET-PG:** * **Hallmark Sign:** The characteristic lesion is a **punched-out ulcer** with smooth, rolled-in edges and a non-reactive base. * **Key Feature:** There is a complete **absence of pain** despite significant corneal damage, which distinguishes it from other types of keratitis. * **Common Causes:** Herpes Zoster Ophthalmicus (most common), Herpes Simplex, and acoustic neuroma surgery (damage to the trigeminal ganglion). * **Management:** Treatment focuses on lubrication, tarsorrhaphy (to protect the cornea), and increasingly, the use of recombinant human nerve growth factor (Cenegermin).

Q: Anterior staphyloma is seen in which of the following conditions?

Sloughing corneal ulcer. **Explanation:** **Anterior Staphyloma** is a condition characterized by the protrusion of a scarred, vascularized pseudocornea lined by iris tissue. It is a late complication of a **sloughing corneal ulcer** (Option A). **Pathophysiology:** When a corneal ulcer leads to total perforation, the aqueous humor escapes, causing the iris to fall forward and plaster against the back of the remaining peripheral cornea or necrotic debris. This "plugging" leads to the formation of a **pseudocornea** (organized exudates and fibrous tissue). Due to the blockage of aqueous drainage, secondary glaucoma develops. The increased intraocular pressure causes this weak, thin pseudocornea to bulge forward, resulting in an anterior staphyloma. **Analysis of Incorrect Options:** * **B. Scleritis:** While severe scleritis can lead to thinning (scleromalacia perforans), it typically results in **intercalary or ciliary staphyloma**, not anterior. * **C. Glaucoma:** While high pressure is necessary for the "bulge," primary glaucoma alone does not cause anterior staphyloma unless there is prior corneal perforation and scarring. * **D. Pathological Myopia:** This is classically associated with **posterior staphyloma**, where the sclera bulges posteriorly at the macula. **High-Yield Clinical Pearls for NEET-PG:** * **Types of Staphyloma:** * **Anterior:** Follows corneal perforation (Sloughing ulcer). * **Intercalary:** At the limbus (up to 2mm from limbus). * **Ciliary:** Over the ciliary body (2–8mm from limbus). * **Equatorial:** At the exit of vortex veins. * **Posterior:** At the posterior pole (Pathological Myopia). * **Management:** Partial staphyloma may be treated with staphylectomy; total staphyloma usually requires **evisceration** or **enucleation** due to the risk of cosmetic disfigurement and lack of visual potential.

Question 1

Neuroparalytic keratitis is most commonly associated with damage to which cranial nerve?

Accepted Answer

Trigeminal nerve (CN V)

Answer

Oculomotor nerve (CN III)

Answer

Abducens nerve (CN VI)

Answer

Facial nerve (CN VII)

Question 2

Corneal ulcer can lead to which of the following complications?

Accepted Answer

Anterior staphyloma

Answer

Posterior staphyloma

Answer

Lenticonus

Answer

Keratoconus

Question 3

A patient presents with acute eye pain and watering for 3 days. Examination reveals a 3x2 mm corneal ulcer with rolled out margins, feathery, finger-like projections, and minimal hypopyon. What is the most likely diagnosis?

Accepted Answer

Fungal keratitis

Answer

Bacterial keratitis

Answer

Acanthamoeba keratitis

Answer

Herpes Simplex Virus keratitis (HSV-I)

Question 4

Neuroparalytic keratitis is associated with paralysis of which cranial nerve?

Accepted Answer

7th cranial nerve

Answer

3rd cranial nerve

Answer

4th cranial nerve

Answer

6th cranial nerve

Question 5

All of the following are signs of mycotic corneal ulcer, EXCEPT:

Accepted Answer

Corneal vascularization

Answer

Large hypopyon

Answer

Sterile immune ring

Answer

Feathery, finger-like extensions into the stroma

Question 6

Which of the following does not cause cornea verticillata?

Accepted Answer

Tay-Sachs disease

Answer

Indomethacin

Answer

Chloroquine

Answer

Fabry disease

Question 7

What is Dellen?

Accepted Answer

Localized thinning of the peripheral cornea

Answer

Raised lesions in the corneoscleral junction

Answer

Age-related macular degeneration

Answer

Marginal keratitis

Question 8

What is the most common cause of anterior staphyloma?

Accepted Answer

Corneal Ulcer

Answer

Herpes Keratitis

Answer

Myopia

Answer

Hypermetropia

Question 9

Which part of the cornea is most affected in neuroparalytic keratopathy?

Accepted Answer

Inferior third of the cornea

Answer

Temporal third of the cornea

Answer

Superior third of the cornea

Question 10

Anterior staphyloma is seen in which of the following conditions?

Accepted Answer

Sloughing corneal ulcer

Answer

Scleritis

Answer

Glaucoma

Answer

Pathological myopia

Diseases of the Cornea — MCQs

Diseases of the Cornea — MCQs

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