What is Photobiomodulation?
Photobiomodulation is known by many names - cold laser therapy, low level light therapy, soft laser therapy, therapeutic laser, and many more. They all describe the same action - the use of electromagnetic energy to affect biological processes.
While this may sound like science fiction, photobiomodulation happens around us all the time. It is the method plants use during photosynthesis as well as how our skin cells form Vitamin D when exposed to sunlight. Laser therapy utilizes a laser-beam of light (meaning very orderly and uniform) to penetrate deeply into tissues and produce positive biological and chemical changes. This light is non-heat-producing and outside the visible light spectrum, somewhere in the 800- to 1,000-nanometer range (the visible spectrum is from 380-750 nanometers).
Lasers are classified based on their ability to cause harm if used improperly. In general, they are classed into 1 of 4 broad classes (I, II, III, IV). Class III and IV lasers are applicable for treatment of superficial lesions and wounds as well as deeper tissues, however Class III require longer treatment times to achieve effective target doses.
What Does Photobiomodulation Do?
The effects of photobiomodulation are a result of photons - packets of electromagnetic energy - interacting with cells. Within cells, certain molecules called chromophores absorb this energy and transfer it into metabolic processes. The results are increased ATP production (ATP is the “fuel” on which cells run), increased levels of nitric oxide and reactive oxygen species, increased metabolic activity, and increased cell growth and reproduction. Photobiomodulation also results in release of endogenous opioids as well as a reduction in neuron impulses leading to a reduction in pain.
Laser therapy also promotes resolution of inflammation by decreasing the release of proinflammatory substances and inducing a transient vasodilation. This allows nutrients to be brought into the area while waste products are flushed out. There is a similar effect on lymph vessels, contributing to lymph drainage and reduction of edema. Also an increased amount of pro-healing cytokines are released. Angiogenesis, fibroblast replication and migration, collagen production, and wound contraction are all also achieved. Photobiomodulation also stimulates bone healing by accelerating the development of new bone and fracture healing.
When To Use Photobiomodulation
Laser therapy is helpful after surgical and dental procedures. Most post-operative patients only require a single treatment immediately after the procedure - such as elective surgeries, minor dental procedures, and closure of minor wounds. More extensive tissue disruption should receive additional treatments (2 to 6) daily or every other day. Laser therapy is also useful for acute or chronic conditions involving pain, inflammation, and healing. Chronic conditions (such as arthritis or disc degeneration) need treatments extending over longer periods of time and are frequently followed by ongoing treatments to maintain effect.
The one absolute contraindication to laser therapy is exposure of the retina by a direct or reflected beam transmitted through the pupil. Laser therapy should also be used with caution over areas into which medication or vaccines have been injected, over a malignancy or surgical site from which a malignancy has been removed, or areas of active hemorrhage. Also, prolonged treatment with high doses should not be used over active bone growth plates, the testicles or uterus, or the thyroid gland.
Classically, treatment over hyperpigmentation, tattoos, and metal implants (TPLO) was seen as unsafe, however studies have shown laser therapy to be safe and indicated in all these scenarios. Also there is no concern with treating patients on photosensitizing medications.
Source: “Laser Therapy: Fact or Fancy”, John C. Godbold, Jr. DVM. Today’s Veterinary Practice. July/August 2019. Pgs 66-69.