Mechanisms of low level light therapy

Michael R. Hamblin, Tatiana N. Demidova

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

347 Citations (Scopus)

Abstract

The use of low levels of visible or near infrared light for reducing pain, inflammation and edema, promoting healing of wounds, deeper tissues and nerves, and preventing tissue damage has been known for almost forty years since the invention of lasers. Originally thought to be a peculiar property of laser light (soft or cold lasers), the subject has now broadened to include photobiomodulation and photobiostimulation using non-coherent light. Despite many reports of positive findings from experiments conducted in vitro, in animal models and in randomized controlled clinical trials, LLLT remains controversial. This likely is due to two main reasons; firstly the biochemical mechanisms underlying the positive effects are incompletely understood, and secondly the complexity of rationally choosing amongst a large number of illumination parameters such as wavelength, fluence, power density, pulse structure and treatment timing has led to the publication of a number of negative studies as well as many positive ones. In particular a biphasic dose response has been frequently observed where low levels of light have a much better effect than higher levels. This introductory review will cover some of the proposed cellular chromophores responsible for the effect of visible light on mammalian cells, including cytochrome c oxidase (with absorption peaks in the near infrared) and photoactive porphyrins. Mitochondria are thought to be a likely site for the initial effects of light, leading to increased ATP production, modulation of reactive oxygen species and induction of transcription factors. These effects in turn lead to increased cell proliferation and migration (particularly by fibroblasts), modulation in levels of cytokines, growth factors and inflammatory mediators, and increased tissue oxygenation. The results of these biochemical and cellular changes in animals and patients include such benefits as increased healing in chronic wounds, improvements in sports injuries and carpal tunnel syndrome, pain reduction in arthritis and neuropathies, and amelioration of damage after heart attacks, stroke, nerve injury and retinal toxicity.

Original languageEnglish
Title of host publicationMechanisms for Low-Light Therapy
DOIs
Publication statusPublished - 2006
Externally publishedYes
EventMechanisms for Low-Light Therapy - San Jose, CA, United States
Duration: 22 Jan 200624 Jan 2006

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume6140
ISSN (Print)1605-7422

Conference

ConferenceMechanisms for Low-Light Therapy
Country/TerritoryUnited States
CitySan Jose, CA
Period22/01/0624/01/06

Keywords

  • Action spectra
  • Biomodulation
  • Biostimulation
  • Cold laser
  • Low level laser therapy
  • Wound healing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology, Nuclear Medicine and Imaging

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