Ophthalmology · Slit-lamp photograph with fluorescein (cobalt blue light)

Dendritic Ulcer (Herpes Simplex Keratitis)

A branching, fluorescein-stained epithelial defect on the cornea — the dendritic ulcer of herpes simplex (HSV) epithelial keratitis.

Cornea under blue light with a bright green branching lesion stained by fluorescein
Dendritic pattern after fluorescein staining.Image: Imrankabirhossain, via Wikimedia Commons — CC BY-SA 4.0.

Written & reviewed by: Kinase Medical Team · Last reviewed: 30 September 2026 · Editorial policy

Key features

  • Branching (dendritic) epithelial lesion with terminal bulbs and swollen borders on slit-lamp examination.
  • Fluorescein shows the dendritic ulceration; rose bengal or lissamine green also stain the lesion.
  • Usually HSV-1; the virus stays latent in the trigeminal ganglion and reactivates, so disease is often recurrent.
  • Repeated attacks can reduce corneal sensation and cause scarring; HSV keratitis is a leading infectious cause of corneal blindness.
  • Treatment: topical antivirals, cycloplegics and oral acyclovir.

Differential diagnosis

Differential diagnosis of Dendritic Ulcer (Herpes Simplex Keratitis)
ConditionHow to tell it apart
Varicella-zoster keratitisCan look similar clinically; PCR of corneal scrapings identified VZV in some lesions labelled HSV.
Acanthamoeba or fungal keratitisAmoebic and fungal keratitis have been misdiagnosed as HSV keratitis; consider them when the lesion is atypical or does not respond to antivirals.

How it appears in NEET PG

Presented as a fluorescein-stained cornea under cobalt blue light; questions ask for the organism, the characteristic shape or the drug to avoid.

Frequently asked questions

Why does a dendritic ulcer stain with fluorescein?

Fluorescein pools wherever the corneal epithelium is broken, so the branching epithelial defect lights up green under cobalt blue light.

Where does herpes simplex virus stay latent in ocular herpes?

In the trigeminal ganglion. Reactivation sends virus back along the sensory nerve to the cornea.

Can steroids be used for a dendritic ulcer?

Antivirals are the treatment. Topical steroids can prolong the infection and risk corneal melting and perforation, so they are used only with extreme caution.

Sources

  1. Azher TN et al. Herpes simplex keratitis: challenges in diagnosis and clinical management. Clin Ophthalmol 2017 (PMC review)
  2. Harrison's Principles of Internal Medicine (textbook)

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For exam preparation and medical education only — not a substitute for clinical judgement, diagnosis or treatment of any patient.