Wood's Lamp in Herpes Zoster Ophthalmicus
Wood's lamp has no established role in the diagnosis or management of herpes zoster ophthalmicus and should not be used for this condition.
Why Wood's Lamp Is Not Indicated
Wood's lamp is an ultraviolet-A light source designed to detect pigmentary changes in the skin, particularly areas of depigmentation that may not be visible to the naked eye in pale skin 1. Its primary validated use is in dermatologic conditions such as vitiligo, where it delineates areas of pigment loss and helps assess disease activity 1.
The device has no diagnostic utility for herpes zoster ophthalmicus because:
- Herpes zoster ophthalmicus is diagnosed clinically by the characteristic periorbital vesicular rash distributed along the ophthalmic division of the trigeminal nerve, not by pigmentary changes 2, 3
- Ocular involvement requires slit-lamp biomicroscopy with fluorescein staining to identify pseudodendritic keratitis, punctate epithelial keratitis, stromal disease, and anterior chamber inflammation 4
- Wood's lamp cannot detect viral keratitis, conjunctivitis, uveitis, or any of the sight-threatening complications of herpes zoster ophthalmicus 4, 2
Essential Diagnostic Approach for Herpes Zoster Ophthalmicus
Instead of Wood's lamp, the correct diagnostic evaluation includes:
Clinical Examination
- Inspect for vesicular rash in the distribution of the first or second trigeminal branch, progressing from maculae and papules to vesicles, pustules, and crusts 3
- Look specifically for Hutchinson's sign (vesicles on the tip of the nose), which indicates nasociliary nerve involvement and predicts higher risk of ocular complications 2
Slit-Lamp Biomicroscopy
- Perform fluorescein staining to identify pseudodendritic lesions (non-excavated, unlike HSV dendrites), punctate epithelial keratitis, and stromal involvement 4
- Assess for anterior chamber inflammation, keratic precipitates, and elevated intraocular pressure 4
Dilated Fundus Examination
- Conduct when posterior segment disease such as acute retinal necrosis or progressive outer retinal necrosis is suspected 4, 3
Common Pitfall to Avoid
Do not confuse Wood's lamp utility in vitiligo (where it is recommended for patients with skin types I and II to assess depigmentation 1) with any role in infectious or inflammatory eye disease. The evidence supporting Wood's lamp is limited to pigmentary disorders 1, and there is no literature suggesting benefit in viral infections of the eye or periocular tissues.
Immediate Management Priority
Once herpes zoster ophthalmicus is diagnosed clinically, initiate systemic antiviral therapy within 72 hours of rash onset—valacyclovir 1000 mg three times daily for 7 days is preferred 4—and refer urgently to ophthalmology for slit-lamp examination and monitoring of ocular complications 4, 2.