Understanding LED Therapy Parameters
excerpt from the book Treating the Face: A Comprehensive Guide for Acupuncturists and Health Professionals By Michelle Gellis
Wavelength, measured in nanometers (nm), determines how deeply the light penetrates the skin. Blue light, which ranges between 415–450 nm, targets the surface layers of the skin and is ideal for treating acne. Red light, at 620–700 nm, penetrates more deeply and is used for collagen stimulation and overall skin rejuvenation. Near-infrared light, often found at 850 nm, penetrates even deeper into soft tissues and joints, making it suitable for musculoskeletal and pain applications.
Irradiance (measured in milliwatts per square centimeter or mW/cm²) reflects the power density, indicating how much energy reaches the skin per second. This helps determine the efficiency of the light delivery.
Joules per square centimeter (J/cm²) measures the total energy delivered during a session. This value is crucial in determining the effectiveness of a treatment. For skin rejuvenation, the optimal energy range is typically between 3 to 6 J/cm². For deeper tissue or chronic pain treatment, effective dosing can reach 20–50 J/cm².
Lumen (lm) measures the visible brightness of a light source but is not an indicator of therapeutic benefit. In LED therapy, therapeutic results depend on wavelength, irradiance, and energy delivery—not brightness. For instance, red light at 640 nm or near-infrared at 850 nm can offer significant therapeutic benefits regardless of how bright the device appears. Even dim light, if at the correct wavelength and power, can stimulate tissue repair. Near-infrared light is invisible but still effective for deep tissue healing.
Summary of Parameters:
- Wavelength (nm): Determines depth of penetration and function
- Irradiance (mW/cm²): Indicates the amount of energy delivered per second
- Joules/cm²: Measures total energy delivered over time
- Lumen (lm): Indicates brightness but not therapeutic efficacy
Therapeutic Application Examples:
- Skin Rejuvenation: 3–6 J/cm² (approx. 2–4 minutes at 30 mW/cm²)
- Mild/Moderate Pain Relief: 20 J/cm² (approx. 11–12 minutes)
- Deep/Chronic Pain Relief: 50 J/cm² (approx. 27–28 minutes)
These metrics ensure accurate dosing and consistent outcomes, allowing clinicians to tailor treatments to individual needs.
