A 32-year-old woman presents with unilateral eye pain, photophobia, and blurred vision for 5 days. Slit-lamp examination reveals dendritiform ulcer with terminal bulbs and swollen eyelid. What is the most common causative agent of viral keratitis?

Question

Accepted Answer

A. Herpes simplex virus type 1. ## Most Common Cause of Viral Keratitis

**Key Point:** Herpes simplex virus type 1 (HSV-1) is the most common cause of infectious keratitis worldwide and the leading cause of corneal blindness in developed nations.

### Clinical Features of HSV Keratitis

| Feature | HSV-1 Keratitis |
|---------|------------------|
| **Ulcer morphology** | Dendritiform (tree-like) with terminal bulbs |
| **Sensation** | Reduced corneal sensation (pathognomonic) |
| **Recurrence** | Common (50% within 5 years) |
| **Laterality** | Usually unilateral |
| **Associated signs** | Vesicular lid involvement, conjunctivitis |

### Epidemiology

**High-Yield:** HSV-1 accounts for ~90% of all herpetic keratitis cases. Primary infection usually occurs in childhood (asymptomatic or mild); recurrent keratitis develops in seropositive individuals due to reactivation of latent virus in trigeminal ganglion.

### Pathogenesis

1. Primary infection → latency in trigeminal nerve
2. Reactivation triggered by stress, fever, immunosuppression, or UV exposure
3. Virus travels along nerve axons to cornea
4. Epithelial ulceration with characteristic dendritic pattern

### Diagnostic Clue

**Clinical Pearl:** The combination of dendritiform ulcer with **reduced corneal sensation** (due to trigeminal nerve involvement) is virtually diagnostic of HSV keratitis. This distinguishes it from other viral causes.

### Treatment Rationale

- **Topical acyclovir** 5 times daily is first-line for epithelial keratitis
- Oral acyclovir for recurrent disease and prophylaxis
- Avoid topical corticosteroids in epithelial disease (risk of geographic ulcer)

**Warning:** Do not confuse HSV keratitis with adenoviral keratoconjunctivitis, which presents with follicular conjunctivitis and subepithelial infiltrates rather than dendritiform ulcers.

Answer

B. Enterovirus 70

Answer

C. Adenovirus

Answer

D. Varicella-zoster virus

A 32-year-old woman presents with unilateral eye pain, photophobia, and blurred vision for 5 days. Slit-lamp examination reveals dendritiform ulcer with terminal bulbs and swollen eyelid. What is the most common causative agent of viral keratitis?

Explanation

Most Common Cause of Viral Keratitis

Clinical Features of HSV Keratitis

Epidemiology

Pathogenesis

Diagnostic Clue

Treatment Rationale

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Feature	HSV-1 Keratitis
Ulcer morphology	Dendritiform (tree-like) with terminal bulbs
Sensation	Reduced corneal sensation (pathognomonic)
Recurrence	Common (50% within 5 years)
Laterality	Usually unilateral
Associated signs	Vesicular lid involvement, conjunctivitis