Wood's Lamp
Wood's Lamp in Pediatric Practice
A Wood's lamp is a diagnostic device that emits long-wave ultraviolet light (UV-A) at 365 nanometers wavelength. It's used to detect various skin conditions, infections, and pigmentation disorders through fluorescence examination.
Key Features
- UV-A light source (365 nm wavelength)
- Nickel oxide filter
- Handheld or mounted design
- Battery-powered or electrical operation
- Built-in magnification (in some models)
Physical Principles
1. Light Properties
- Ultraviolet Spectrum
- UV-A wavelength: 365 nm
- Penetrates superficial skin layers
- Causes specific substances to fluoresce
- Fluorescence Mechanism
- Excitation of fluorescent compounds
- Emission of visible light
- Specific color patterns
2. Technical Specifications
- Filter Components
- Wood's glass (barium silicate)
- Nickel oxide content
- Blocks visible light
- Light Output
- Intensity: 4-10 watts
- Coverage area: 10-15 cm diameter
- Operating life: 5000-10000 hours
Examination Technique
1. Room Preparation
- Environmental Requirements
- Complete darkness essential
- Allow 1-2 minutes for dark adaptation
- Remove reflective surfaces
- Equipment Setup
- Warm-up period: 1-2 minutes
- Distance: 4-5 inches from skin
- Angle: 90 degrees to surface
2. Patient Preparation
- Pre-examination Steps
- Remove makeup/creams
- Clean examination area
- Explain procedure to child/parent
- Positioning
- Comfortable, stable position
- Access to examination areas
- Child-friendly approach
Clinical Applications
1. Infection Diagnosis
- Fungal Infections
- Tinea capitis (blue-green)
- Tinea versicolor (yellow-gold)
- Microsporum canis (bright green)
- Bacterial Infections
- Pseudomonas (green)
- Erythrasma (coral red)
- Propionibacterium (orange-red)
2. Pigmentation Disorders
- Depigmentation
- Vitiligo (enhanced white)
- Ash leaf spots (bright white)
- Hypopigmentation assessment
- Hyperpigmentation
- Melasma evaluation
- Post-inflammatory changes
- Café-au-lait spots
Diagnostic Findings
1. Color Interpretation Guide
- Fluorescent Colors
- Blue-green: Dermatophytes
- Yellow-gold: Malassezia furfur
- Coral red: Corynebacterium minutissimum
- Bright white: Vitiligo/TSC spots
- Green: Pseudomonas
- Normal Findings
- Blue: Normal skin oils
- White: Normal skin
- Dark purple: Normal hair
2. Documentation Guidelines
- Essential Elements
- Location of findings
- Color and pattern description
- Size and distribution
- Comparison with normal skin
- Follow-up Assessment
- Treatment response monitoring
- Progress documentation
- Pattern changes over time
3. Common Pitfalls
- False Positives
- Soap residue
- Moisturizer remnants
- Deodorant/cosmetics
- False Negatives
- Insufficient darkness
- Recent topical medications
- Inadequate lamp distance
