ABSTRACT
In 1967, a few years a²er the ›rst working laser was invented, Endre Mester in Hungary wanted to test if laser radiation might cause cancer in mice (Mester et al. 1968). He shaved the dorsal hair, divided them into two groups, and gave a laser treatment with a low powered ruby laser (694 nm) to one group. ™ey did not get cancer and to his surprise the hair on the treated group grew back more quickly than the untreated group. ™is was the ›rst demonstration of “laser biostimulation.” Since then, medical treatment with coherent light sources (lasers) or noncoherent light sources consisting of ›ltered lamps or light-emitting diodes (LED) has spread throughout the world. Currently, low level laser (or light) therapy (LLLT), also known as “cold laser,” “so² laser,” “biostimulation,” or “photobiomodulation,” is routinely practiced as part of physical therapy and is under investigation for many serious conditions and even life-threatening diseases. In fact, light therapy is one of the oldest therapeutic methods used by humans (historically as solar therapy by Egyptians, later as UV therapy for which Nils Finsen won the Nobel prize in 1904 (Roelandts 2002) ). ™e use of lasers and LEDs as light sources was the next step in the technological development of photomedicine and phototherapy. In LLLT, the question is no longer
whether light has biological ežects, but rather how energy from therapeutic lasers and LEDs works at the cellular and organism levels and what are the optimal light parameters for dižerent uses of these light sources.
