Irradiance, dose, and fluence determine how much light a skin surface actually receives much more than wattage alone. Therefore, these concepts are important when you want to compare red light therapy devices fairly.
What is irradiance?
Irradiance describes how much optical power falls on a given surface and is usually expressed in mW/cm².
What is fluence or energy dose?
Fluence is the amount of energy per unit area and is often expressed in J/cm². Simply put: fluence = irradiance × time.
Why wattage is not enough
Electrical power does not directly indicate how much light energy your skin receives. Optics, distance, LED efficiency, and treatment surface also play a role.
Why distance is important
Irradiance can change when you stand closer to or further from a device. Therefore, you should always evaluate a protocol based on the recommended measurement distance.
Is more always better?
No. PBM uses specific parameters; unlimited more light does not automatically mean better results.
What to look for?
- Wavelength(s)
- Irradiance
- Distance
- Treatment time
- Treatment area
- Instructions for use
Conclusion
Do not compare red light devices based on wattage alone. Look at the complete light protocol.
Sources: PBM consensus and umbrella review of RCTs.