What is it?

More recently, the term “photobiomodulation” has been used to refer to laser therapy, literally: photo=light, bio=biologic, modulation=change.

So the definition of photobiomodulation is the use of light to cause biologic changes to influence healing (1).

Visible light falls into a spectrum of wavelengths, from 400-700nm, traveling in different phases and directions (ie. incoherent) (1,3). For perspective, violet light is a wavelength of 400nm and green is 510nm. Non-visible light includes ultraviolet with shorter than 400nm and infrared with longer than 700nm (1). To effect biologic change, laser light must be monochromatic (1 single wavelength), coherent (photon packets of energy are travelling in the same phase and direction), and collimated (so there is minimal parting of the beams that would lead to loss of energy over time). Therapy lasers may have multiple components in order to provide multiple wavelengths, but each component only produces one wavelength. This allows the absorption of light to be targeted very specifically to wavelength dependent chromophores (photon receptors sitting on the membranes of mitochondria, which are important energy and protein generators in the cells of the body), thereby targeting specific tissues. Coherence and collimation allow for precision treatment, reducing the risk of heat damage or other side effects (2). All of these properties allow laser light to penetrate into specific tissues for therapeutic benefit (3).