Viral Keratitis

Intro & Etiology - Tiny Terrors

• Viral keratitis: Corneal inflammation caused by viruses; a significant cause of ocular morbidity & blindness.
• Etiology (Tiny Terrors):
  • Herpes Simplex Virus (HSV): Types 1 & 2; most common cause of infectious corneal blindness in developed countries.
    • HSV-1: Primarily orofacial, causes most ocular herpes.
    • HSV-2: Primarily genital, can cause ocular disease (neonatal).
  • Varicella-Zoster Virus (VZV): Causes Herpes Zoster Ophthalmicus (HZO).
  • Adenovirus: Causes Epidemic Keratoconjunctivitis (EKC) & Pharyngoconjunctival Fever (PCF).
  • Others: Cytomegalovirus (CMV), Epstein-Barr virus (EBV), Molluscum contagiosum.

⭐ HSV keratitis is notorious for its recurrent nature, often triggered by stress, fever, or immunosuppression, leading to progressive corneal scarring and vision loss if not managed appropriately.

• Classification (Basic):
  • Primary infection
  • Recurrent infection

Herpes Simplex Keratitis - Dendritic Deception

• HSV-1 (common), latent in trigeminal ganglion; reactivation causes recurrent keratitis. Major cause of infectious corneal blindness.
• Types & Features:

  Type	Key Features & Signs
  Epithelial	Dendritic Ulcer: Pathognomonic. Linear, branching, terminal bulbs. Stains fluorescein (base), Rose Bengal (edges). 📌 Dead Epithelial Ridges Rose Bengal. ↓Corneal sensation. Geographic Ulcer: Large, ameboid.
  Stromal	Interstitial Keratitis (IK): Immune, non-necrotizing. Stromal haze, ghost vessels. Disciform Keratitis (Endotheliitis): Central disc edema, KPs, Wessely ring.
  Uveitis	Anterior, ↑IOP. Often with stromal/endothelial disease.

• Management:

⭐ Topical steroids alone can worsen epithelial HSK (dendritic/geographic ulcers), leading to a "geographic" ulcer and ↑risk of stromal involvement/perforation.

Varicella Zoster & Others - Zoster's Sting & More

• Varicella Zoster Keratitis (VZK): Reactivation of VZV in the trigeminal ganglion.

  • 📌 Hutchinson's sign: Vesicles on tip/side/root of nose (nasociliary nerve involvement) → indicates ↑ risk of ocular involvement.

  • Corneal lesions: Pseudodendrites (raised, heaped-up epithelial cells, stain poorly with fluorescein but well with Rose Bengal, no terminal bulbs), nummular or disciform keratitis (immune), endothelitis, uveitis, neurotrophic keratopathy.

  • Treatment: Oral antivirals (e.g., Valacyclovir 1g TID, Acyclovir 800mg 5x/day for 7-10 days). Topical steroids for stromal/immune keratitis or uveitis, always under systemic antiviral cover. ⭐ > VZV pseudodendrites are typically elevated, stain poorly with fluorescein but well with Rose Bengal, and lack terminal bulbs, distinguishing them from HSV dendrites.

• Other Viral Keratitis:

  • Adenovirus: Highly contagious.
    • Epidemic Keratoconjunctivitis (EKC): Serotypes 8, 19, 37. May cause subepithelial infiltrates (SEIs) affecting vision.
    • Pharyngoconjunctival Fever (PCF): Serotypes 3, 4, 7. Associated with fever, pharyngitis, follicular conjunctivitis.
  • Molluscum Contagiosum: Umbilicated lesions on lid margin can shed viral particles → chronic follicular conjunctivitis, superficial keratitis. Treatment involves addressing lid lesions (e.g., excision, cryotherapy).

Diagnosis & Management - Viral Defense

• Diagnosis:
  • Clinical: ↓ sensation, dendritic (HSV) / pseudodendritic (VZV) ulcers.
  • Stains: Fluorescein, Rose Bengal (devitalized cells).
  • Lab: PCR (gold standard), Giemsa (giant cells).
• Management:
  • Antivirals: Topical (Acyclovir 3%, Ganciclovir 0.15%). Oral (Acyclovir 400mg HSV / 800mg VZV 5x/day).
  • Steroids: For stromal/disciform (Prednisolone 1%). MUST use with antivirals. Avoid in active epithelial lesions.
  • Cycloplegics: (Homatropine) for pain.
  • Debridement: ↓ viral load in dendritic ulcers.

⭐ Dendritic ulcer with terminal end bulbs is pathognomonic for HSV keratitis; stains with fluorescein (ulcer base) and Rose Bengal (infected epithelial cells at margin).

High‑Yield Points - ⚡ Biggest Takeaways

• HSV is the leading cause of viral keratitis, presenting with dendritic ulcers.
• Reduced corneal sensation is a hallmark sign.
• Treat epithelial HSV with topical antivirals (e.g., Acyclovir).
• Topical steroids: contraindicated in active epithelial HSV; used for stromal disease with antiviral cover.
• Disciform keratitis (stromal edema) and uveitis are common HSV complications.
• HZO keratitis is often preceded by Hutchinson's sign.
• Risk of neurotrophic keratopathy post-infection_._