A corneal dendrite — a branching, tree-like epithelial lesion — is one of the most pattern-recognition-dependent findings in ophthalmology. The classic teaching is "dendrite = herpes simplex," but a meaningful minority of dendritiform lesions are pseudo-dendrites with entirely different causes and treatments. Misdiagnosing a pseudo-dendrite as HSV (or vice versa) can delay correct treatment or, worse, worsen the underlying condition.
True HSV dendritic ulcer: clinical features
- Linear branching epithelial defect with terminal bulbs at each branch end — this is the single most reliable distinguishing feature
- Swollen, heaped-up margins containing live virus (the base does not typically stain with fluorescein as densely as the margins do with rose bengal)
- Decreased corneal sensation is common and a useful supporting sign
- Fluorescein stains the defect itself; rose bengal or lissamine green stains the virus-laden margins
- Recurrence is the rule, not the exception — ask about prior episodes
Anatomic classification (AAO framework)
Rather than relying on inconsistent older terminology, HSV keratitis is now classified simply by which corneal layer is principally involved, since this directly determines treatment:
| Category | Key feature | Core treatment |
|---|
| Epithelial keratitis (dendritic / geographic) | Live viral replication in epithelium | Antiviral only |
| Stromal keratitis | Immune-mediated stromal inflammation, +/- necrosis | Antiviral + topical corticosteroid (steroid only after antiviral cover established) |
| Endothelial keratitis (disciform) | Endothelial inflammation with stromal/epithelial edema, keratic precipitates, no significant anterior chamber reaction | Antiviral + topical corticosteroid |
Current treatment (epithelial/dendritic disease)
- Topical: Ganciclovir 0.15% gel five times daily, OR trifluridine 1% drops nine times daily, tapered over 2-3 weeks as the epithelium heals
- Oral alternative (useful when compliance with frequent topical dosing is a concern, or in children): Acyclovir 400 mg five times daily or valacyclovir, for 7-10 days
- Debridement of loose, infected epithelium at the dendrite edge (after topical anesthesia) can hasten healing and reduce viral load — a useful adjunct, not a replacement for antivirals
- Avoid topical corticosteroids in pure epithelial disease — they promote viral replication and can convert a self-limited dendrite into a geographic ulcer
- Consider oral antiviral prophylaxis (e.g., acyclovir 400 mg twice daily for several months) in patients with frequent recurrences
- Red flag: a dendritiform ulcer that is non-healing, worsening, or increasingly painful despite appropriate antiviral therapy should raise suspicion for Acanthamoeba keratitis — reassess the diagnosis rather than simply extending antiviral treatment
Pseudo-dendrites: the differential diagnosis
These lesions look dendritiform but lack true terminal bulbs, tend to be more plaque-like or heaped-up, and — critically — do not respond to antivirals. Consider:
- Herpes zoster ophthalmicus (HZV) pseudo-dendrites — mucous plaque-like, raised, lack the discrete terminal bulbs of HSV; look for a vesicular rash in the V1 dermatome and Hutchinson's sign
- Healing epithelial defect after abrasion or recurrent erosion — epithelial regeneration lines can mimic a dendrite
- Neurotrophic keratopathy and persistent epithelial defect — often a consequence of recurrent HSV itself, so past herpetic disease doesn't exclude this as the current cause
- Thygeson's superficial punctate keratitis
- Limbal stem cell deficiency
- Exposure keratopathy
- Drug/toxin-related: topical beta-blocker toxicity; cornea verticillata from amiodarone or Fabry disease (whorl-like, not truly dendritic, but sometimes confused)
- Tyrosinemia (rare, but classically produces pseudo-dendrites in children)
The single most useful bedside discriminator remains careful slit-lamp assessment for true terminal bulbs and corneal sensation testing — reduced sensation strongly favors true HSV.
Key references: American Academy of Ophthalmology. Herpes Simplex Virus Keratitis: A Treatment Guideline. | Merck Manual Professional Edition, Herpes Simplex Keratitis. | UpToDate, Herpes simplex keratitis (last updated Jan 2025).