Definition: An infection of the cornea caused by the herpes simplex virus (HSV).

Epidemiology:

  • Most frequent cause of corneal blindness in the United States
  • Most common source of infectious blindness in the Western world. Approximately 2 million people worldwide have impaired vision from herpetic eye disease (Farooq 2012)

Pathophysiology:

  • Primary infection: occurs most commonly in the mucocutaneous or ocular distribution of the trigeminal nerve, and can present as a non-specific upper respiratory infection
  • Latency: the virus spreads from the infected epithelial cells to the cell body in the trigeminal ganglion where the virus persists indefinitely in a latent state
  • Reactivation: interneuronal spread of HSV within the ganglion allows patients to develop subsequent ocular disease without ever having had primary ocular HSV infection

    Corneal Layers - emaze.com

    Corneal Layers – emaze.com

  • HSV keratitis can be divided into 3 types: epithelial, stromal, and endothelial (White 2014)
    • Epithelial: caused by actively replicating virus and occurs in the outermost layer of the cornea
    • Stromal: caused by immune mechanisms and occurs in deeper layers
    • Endothelial: caused by chronic inflammation and occurs in deeper layers
  • Sequelae: Recurrent HSV keratitis can cause corneal scarring, ulceration, and perforation, ultimately leading toastigmatism and permanent vision loss.

Pic 2 - dendritic lesions optometrist.com.auSymptoms:

  • Eye pain
  • Corneal injection
  • Visual changes (blurry vision, decreased visual acuity)
  • Tearing
  • Discharge
  • Photophobia

Physical exam:

  • Visual acuity should be performed in all patients
  • Fluorescein staining
    • May reveal dendritic lesions (linear branching patterns with terminal bulbs)
    • If the lesion enlarges, it can form a geographic ulcer
  • Slit lamp exam
    Geographic Ulcer - lasereyeconsultant.co.uk

    Geographic Ulcer – lasereyeconsultant.co.uk

    • Used to identify disease in deeper (stromal + endothelial) layers
    • Stromal disease shows up primarily as an inflammatory infiltrate with stromal edema, vascularization, and scarring

Diagnostics:

  • The diagnosis of HSV keratitis is based on clinical eye exam.
  • In the absence of dendritic lesions, decreased corneal sensation should increase concern for herpetic keratitsis (Weiner 2013)
  • Viral culture
    • Gold standard test
    • Impractical in the ED: expensive, delayed
  • Ophthalmology may perform additional testing, such as viral culture/PCR and Tzanck smear, to confirm the diagnosis but these are not routinely recommended (Welder 2012)
  • Pitfalls: these tests are only positive when live virus is present, and cannot be used to diagnose stromal keratitis (White 2014)

Management:

  • Most cases of HSV epithelial keratitis resolve spontaneously within 3 weeks. However, the American Academy of Ophthalmology recommends treatment of epithelial keratitis to prevent recurrence and progression to stromal or endothelial keratitis.
  • Epithelial keratitis:
    • Trifluridine 1% solution: 1 drop Q2hours for 7 days OR
    • Ganciclovir 0.15% gel: five times per day
    • Oral antiviral agents (not FDA approved, but equal efficacy in studies) (Wilhelmus 2010)
    • Corneal debridement
  • Stromal and endothelial keratitis:
    • Urgent referral to ophthalmology
    • Topical corticosteroid
    • Oral antiviral agents for 10 weeks as prophylaxis reduces the rate of recurrent herpetic keratitis (Wilhelmus 1999)

Take Home Points:

  • Fluorescein is an essential tool in the diagnosis of HSV keratitis
  • Identifying the type of HSV keratitis is crucial, as it will guide treatment
  • Update tetanus vaccination
  • Consult ophthalmology if there is concern for HSV keratitis as these patients require close and frequent follow-up

References:

Farooq AV et al. Herpes simplex epithelial and stromal keratitis: an epidemiologic update. Surv Ophthalmol 2012; 57(5):448-462. PMID: 3652623

Wilhelmus KR et al. Antiviral treatment and other therapeutic interventions for herpes simplex virus epithelial     keratitis. Cochrane Database Syst Rev 2010; (12): CD002898. PMID: 4739528

Weiner et al. Demystifying the ocular herpes simplex virus. American Academy of Ophthalmology. Link

McDonald et al. Management of epithelial herpetic keratitis: an evidence based algorithm. Link

Welder et al. Herpes simplex keratitis. University of Iowa Health Care. Link

Wilhelmus KR et al. Herpetic Eye Disease Study. A controlled trial of topical corticosteroids for herpes simplex stromal keratitis. Ophthamology 1999; 101(12):1883-1896. PMID: 7997324

Chan RV et al. Herpes simplex keratitis – Latin America. American Academy of Ophthalmology. Link

White et al. Herpes simplex keratitis: A treatment guideline – 2014. Link