Herpes simplex

• Herpes simplex virus (HSV) infection is the most common cause of keratitis and is called herpes simplex keratitis.
• HSV-1 = eye, lips and face

  HSV-2 = genital infection with rare ophthalmic involvement
• Primary infection with HSV is usually acquired in childhood and is commonly subclinical or mild with symptoms of blepharoconjunctivitis and upper respiratory tract infections.
• Following the resolution of the primary infection, HSV travels through the sensory nerve to the trigeminal ganglion, establishing latency.
• Risk factors for herpes simplex virus infection include:

  • Primary infection: direct contact with infected secretions or lesions
  • Reactivation/ recurrent disease: trauma involving the trigeminal nerve, stress, immunosuppression, previous reactivation
• Typical symptoms of herpes simplex epithelial keratitis include:

  • As with other forms of keratitis: discomfort, grittiness, red eye, reduced visual acuity and photophobia
  • Epiphora (watering of the eye) as opposed to purulent discharge seen in bacterial ulcer
  • A previous history of cold sores
• Typical clinical findings on examination may include:

  • Lids and lashes: mild eyelid erythema and oedema
  • Conjunctiva: diffuse or circumlimbal injection
  • Cornea: dendritic ulcer (pathognomonic sign) with linear branching morphology and terminal bulbs. The bed of the ulcer will stain green with fluorescein, while the ulcer margin will stain with rose Bengal
  • Reduced corneal sensation
• Viral keratitis will show a positive fluorescein stain (dendritic ulcer) while bacterial keratitis will not.
• HSV keratitis can be diagnosed clinically with the identification of a dendritic ulcer.

  Conjunctival and corneal swabs can be sent for a confirmatory viral PCR. It is however important to investigate other microbial causes of keratitis when the diagnosis is equivocal.
• Management:

  • Discontinue contact lens
  • Topical antivirals
  • Epithelial debridement
  • Steroids are contraindicated in active epithelial disease
  • May need long term oral antiviral prophylaxis in recurrent disease
• The majority of dendritic ulcers will resolve even without treatment. Prolonged or recurrent disease may result in corneal scarring, glaucoma, and cataracts.