Wood’s Light Examination
The Wood’s Light Examination is a useful and inexpensive tool in clinical practice. It is powered by alternating or direct current that converts ultraviolet light into visible light, and it usually has an accompanying magnification lens. It provides a simple diagnostic method in the evaluation of
● Many dermatological problems
● Fluorescein-staining evaluation of eye injuries
OVERVIEW
● Most common dermatological lesions that fluoresce are listed on the table below.
● Detection of chemicals applied to the skin. Affected areas are a different color from that of the surrounding skin.
● Prior cleansing of the area to be examined causes false-negative result.
● Certain skin lesions do not fluoresce.
● Systemic antibiotic therapy, such as with tetracyclines, can cause fluorescence in some lesions.
● Cosmetics present on the skin interfere with fluorescence.
● Detection of eye injuries with fluorescein. When applied to the eye, fluorescein has a higher concentration of uptake in areas in which there has been disruption of the cornea or sclera. Under a Wood’s light, the injured area fluoresces as a bright yellow-green.
● Detection of porphyrins in the urine. These appear bright red.
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Fluorescence of Lesions and Parasites With the Wood’s Light
| LESION | FLUORESCENCE |
|---|---|
| Erythrasma | |
| Corynebacterium minutissimum | Varying shades of pink to coral red |
| Tinea Capitis (Three Varieties) | |
| Microsporum audouinii | Brilliant green |
| M. canis | Brilliant green |
| Trichophyton schoenleinii | Pale green |
| Tinea Versicolor | Yellow to deep green |
| Pseudomonas aeruginosa | Blue green to green |
| Pigmentation Alterations | |
| Albinism | Cold bright white |
| Ash-leaf spot of tuberous sclerosis | Blue-white |
| Depigmentation | Cold bright white |
| Hypopigmentation | Blue-white |
| Hyperpigmentation | Purple-brown |
| Leprosy | Blue-white |
| Vitiligo | Blue-white |
| Squamous cell carcinoma* | Bright red |
| Common Parasitic Infestations | |
| Scabies | Magnification of track and/or mite |
| Pediculosis (capitis, corporis, pubis) | Visualization of louse |
* The diagnosis of this dermatological disorder should be made by pathological assessment.
RATIONALE
● Skin—To allow the clinician to differentiate dermatological presentation of types of bacterial, fungal, and pigmented lesions found on the skin
● Eye—To allow the visual assessment of injuries to the cornea and conjunctiva with fluorescein staining
● Urine—To screen for porphyria—a rare metabolic disorder
● Clinical evaluation of dermatitis, the eye, or urine by the unaided eye alone may result in an inappropriate assessment and render an unsuccessful treatment regimen.
INDICATIONS
● Skin or hair lesions
● Corneal abrasion
● Suspicion of porphyria
CONTRAINDICATIONS
● None
PROCEDURE
Wood’s Light—Skin
Equipment
● Wood’s light
● Darkened room
Procedure
● Have the client position himself or herself comfortably.
● Explain to the client that the Wood’s light has the same characteristics as a typical black light; the room will be darkened, and the black light will be turned on to examine for fluorescence of the lesion in question.
● Have all lights turned off.
● Hold the Wood’s light approximately 6 to 8 inches from the lesion in question, and observe the characteristics of the fluorescence of the lesion.
BIBLIOGRAPHY
Driscoll C, Bope ET. The Family Practice Desk Reference. 4th ed. St. Louis, MO: Mosby; 2002.
Habif T. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. St. Louis, MO: Mosby; 2011.
Murtagh J. Practice Tips. 5th ed. New York, NY: McGraw-Hill; 2008.
Pfenninger JL, Fowler GC. Procedures for Primary Care Physicians. St. Louis, MO: Mosby; 2011.
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