Related Subjects:
|Episcleritis
|Scleritis
|Assessing a Red eye
|Acute Angle Closure Glaucoma
|Allergic and Infective Conjunctivitis
|Anterior and Posterior Uveitis
|Herpes simplex keratitis (HSK)
⚠️ Always exclude viral retinitis after dilatation in immunocompromised patients (e.g. HIV, transplant) - this requires emergency same-day referral.
📍 About
- Herpes Simplex Keratitis (HSK) is a corneal infection with HSV, usually HSV-1.
- Most common form: epithelial keratitis (50–80% of ocular herpes cases).
- Other forms: blepharoconjunctivitis, stromal keratitis, iridocyclitis, acute retinal necrosis.
🦠 Aetiology
- Reactivation of latent HSV-1 in the trigeminal ganglion.
- Triggers: stress, fever, UV exposure, menstruation, immunosuppression, certain medications.
- Atopic patients are prone to severe or bilateral disease.
🩺 Clinical Features
- History: cold sores, recurrent red eye, immunosuppression.
- Symptoms: foreign body sensation, watery discharge, photophobia, red eye.
- Usually unilateral; bilateral cases suggest severe atopy or immunosuppression.
🔎 Types of HSK
- Epithelial: Classic dendritic ulcer. Branching pattern with fluorescein uptake; reduced corneal sensation. Risk of “geographic” ulcer if mismanaged with steroids.
- Stromal: Necrosis, infiltrates, vascularisation, keratic precipitates, raised IOP.
- Disciform: Central stromal thickening, epithelial oedema, Descemet’s folds, keratic precipitates.
- Metaherpetic (trophic) ulcer: Poor healing due to corneal denervation or drug toxicity → chronic epithelial defect.
💡 Always use fluorescein to confirm epithelial defect.
Look for dendritic branching pattern.
Recurrent episodes may cause corneal scarring and permanent visual loss.
🧪 Investigations
- Diagnosis is usually clinical.
- Corneal swab/biopsy for HSV PCR if uncertain.
🔀 Differentials
- Herpes zoster ophthalmicus.
- Bacterial keratitis.
- Fungal keratitis.
- Acanthamoeba keratitis (contact lens wearers).
💊 Management
- Avoid topical steroids alone - they worsen epithelial disease.
- Epithelial HSK: Topical aciclovir 3% ointment or ganciclovir 0.15% gel 5×/day. Urgent referral within 1–2 days.
- Recurrent HSK: Treat as above; beware stromal involvement → same-day referral.
- Stromal/disciform disease, bilateral cases, children, or contact lens wearers: Emergency same-day ophthalmology referral.
- Severe disease: May need systemic antivirals ± cautious topical steroids under specialist supervision.
- Surgical: Debridement for epithelial ulcers; corneal graft (PKP) for scarring in quiescent disease.
👁️ Patient Advice
- Avoid touching/rubbing eyes during cold sore outbreaks.
- Do not use steroid eye drops unless under specialist supervision with antiviral cover.
- Stop wearing contact lenses until completely healed.
⚠️ Complications
- Corneal scarring, thinning, or perforation.
- Recurrent uveitis.
- Secondary glaucoma.
- Permanent visual impairment.
📚 References
📌 Summary
Herpes Simplex Keratitis (HSK) = dendritic ulcer on fluorescein, reduced corneal sensation, risk of scarring with recurrences.
🚫 Steroids worsen epithelial HSK.
✅ Start topical antivirals promptly.
📅 Urgent ophthalmology referral if stromal disease, immunocompromised, or recurrent infection.
