LASER THERAPY TERMINOLOGY
“Cold Laser”, “Low-Level Laser Therapy (LLLT)”, and “Low-Intensity Laser Therapy (LILT)” are all terms commonly used in the laser therapy field. 5 In general, these terms refer to “treatment using irradiation with light of low power intensity so that the effects are a response to the light and not due to heat.” 6 With the recent advancement of laser technology producing higher power devices (>0.5 W), another term, “High-Intensity Laser Therapy (HILT),” has entered the scientific literature and clinical space. HILT can create warmth on the surface of the skin during treatment but the main mechanism of action, like with the lower power lasers, is biochemical effects from light rather than heat. Unfortunately, these terms do not comprehensively describe the mechanisms related to therapy lasers, nor do they adequately distinguish them from other light-based therapies. This lack of clarity has led to significant confusion about the laser modality and a need for better nomenclature. 5 In September 2014, the North American Association for Light Therapy (NAALT) and the World Association for Laser Therapy (WALT) convened and agreed upon the term “Photobiomodulation Therapy” as the preferred nomenclature. Photobiomodulation Therapy (PBM) was added to the MeSH database in November 2015 and is the preferred name for researchers and key opinion leaders in the field because it more clearly characterizes the modality. 5 Even with this declaration from the laser therapy organizations, a variety of terms continue to be used and confusion remains. The key point is that laser therapy, no matter the terminology used, affects the body through a process called photobiomodulation (PBM). “PBM is the mechanism by which nonionizing optical radiation in the visible and near-infrared spectral range is absorbed by endogenous chromophores to elicit photophysical and photochemical events at various biological scales without eliciting thermal damage.” 7 It is a mechanism that leads to “physiological changes and therapeutic benefits,” 7 such as relief from muscle pain, arthritis, joint stiffness, and muscle spasm.
While both high and low power lasers can deliver photobiomodulation therapy, it is important to note that high power lasers differentiate themselves from their low power counterparts. HILT not only provides photobiomodulation therapy, but it also alleviates pain and stiffness through heat. HILT can reach deeper target tissues and reduce treatment times due to the higher power, and recent studies demonstrate that HILT can give patients better results than those treated with a low power laser. 7,8,9
Low Intensity Laser
High Intensity Laser
Power increases with HILT
Volume of photons per second at target depth increases with HILT
Treatment time decreases with HILT
Heat
Stimulating Cellular Activity via Photobiomodulation
Heat becomes an additional mechanism of action with HILT
Read on for summaries of recent research supporting the use of photobiomodulation therapy for common clinical conditions.
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