Photobiomodulation

Photobiomodulation, also known as low level laser therapy (LLLT), cold laser therapy, and laser biostimulation, is an emerging medical and veterinary technique in which exposure to low-level laser light can stimulate or inhibit cellular function leading to beneficial clinical effects.^[1] The technique is also known by the more ambiguous terms phototherapy and laser therapy, which may also be used to describe other medical techniques. The "best" combination of wavelength, intensity, duration and treatment interval is complex and sometimes controversial with different diseases, injuries and dysfunctions needing different treatment parameters and techniques. These are still being explored and increasingly published by the academic community.

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History

In 1967 a few years after the first working laser was invented, Endre Mester in Semmelweis University experimented with the effects of lasers on skin cancer. While applying lasers to the backs of shaven mice, he noticed that the shaved hair grew back more quickly on the treated group than the untreated group.^[2]

Clinical applications

Clinical applications include treating soft tissue injury, chronic pain, wound healing and nerve regeneration, and possibly even resolving viral and bacterial infections. One clinical application showing great promise is the treatment of inflammation, where the anti-inflammatory effect of location-and-dose-specific laser irradiation produces similar outcomes as NSAIDs, but without the potentially harmful side-effects.^[3]

Mechanism

Certain wavelengths of light at certain intensities (delivered by laser, LED or another monochromatic source) will aid tissue regeneration, resolve inflammation, relieve pain and boost the immune system.^{[citation needed]} The exact mechanism is still being explored and debated but it is agreed that the mechanism is photochemical rather than heat-related.^{[citation needed]} Observed biological and physiological effects include changes in cell membrane permeability, up-regulation and down-regulation of adenosine triphosphate and nitric oxide.

Contentious areas are: "the best" wavelength, dose, dose-rate effects, beam penetration, the role of coherence and pulses (peak power and repetition rates). Laser average power is typically in the range of 1-500 mW; some high peak power, short pulse width devices are in the range of 1-100 W with typically 200 ns pulse widths. The average beam irradiance then is typically 10 mW/cm² - 5 W/cm².^{[citation needed]} The wavelength is typically in the range 600-1000 nm but some research has been done and products are available outside this range.

Safety

See also: laser safety

During the use of lasers, doctors operator and patient normally wear dense filter spectacles in case of accidental or reflected exposure to avoid damaging the eye.

See also

• Photomedicine
• Light therapy

References

• Tuner, Jan and Hode, Lars, The Laser Therapy Handbook.