A critical review of low energy laser bioeffects

The biological and medical effects of low energy laser and sources of non-ionizing radiation, inaccurately known as 'biostimulation', have been receiving wider attention recently. This is undoubtedly due to the previously disparaging claims which were made in this field being proven to be at least partially correct. This modality of therapy is now in relatively common use mainly in Europe where it gave rise to a thriving low energy laser industry. Even in the USA, low energy laser therapy is gaining momentum and is the subject of some extensive controlled clinical trials. Until those and other scientific medical triasl become publicm, it can be said, with a few reservations, that a large proportion of the published research on the bioeffects of low energy lasers, especially that dealing with treatment of diseases, has not been performed to rigorous scientific standards. Consequently, the data had been published mostly in peripheral journals and the scientific and medical community grouped 'biostimulation' with such suspected modalities of therapy as acupuncture and worse (the use of He-Ne laser for acupuncture did not help to clarify the situation). This attitude to low energy laser effects resulting in misunderstanding and neglect, which exacerbated the alienation of the subject from mainstream science and medicine, as well as to the fact that the few established biological phenomena associated with low energy light effects remained on a phenomenal level of knowledge and to the absence of concrete theory as to their mechanisms. In this article we shall attempt to critically review most of the available data regarding the interaction of low energy laser radiation with tissues. The therapeutic effects of this modality of treatment on patients and diseases wil be the subject of another review. The present review will not cover the parts of the field of photobiology dealing with subcellular events and most of the field of microbeam cellular surgery, but will concentrate on medically applicable phenomena only. It must be emphasized that although most of the experiments described were performed using laser radiation, it is not clear whether coherent radiation is essential for those responses. It is not unlikely that some or most of the phenomena described below can be achieved with non-coherent narrow-band sources.