Dr. Kendric C. Smith at the Department of Radiation Oncology, Stanford University School of Medicine, concludes in an article entitled The Photobiological Effect of Low Level Laser Radiation Therapy (Laser Therapy, Vol. 3, No. 1, Jan - Mar 1991) that "1) Lasers are just convenient machines that produce radiation. 2) It is the radiation that produces the photobiological and/or photophysical effects and therapeutic gains, not the machines. 3) Radiation must be absorbed to produce a chemical or physical change, which results in a biological response."

Light therapy has also been given the name "phototherapy". A study done by the Mayo Clinic in 1989 suggests that the results of light therapy are a direct effect of light itself, generated at specific wavelengths, and are not necessarily a function of the characteristics of coherency and polarization associated with lasers. In a study entitled Low-Energy Laser Therapy: Controversies and New Research Findings, Jeffrey R. Basford, M.D. of the Mayo Clinic's Department of Physical Medicine and Rehabilitation, suggests that the coherent aspect of laser may not be the source of its therapeutic effect. He states "firstly, the stimulating effects (from therapeutic light) are reported following irradiation with non-laser sources and secondly, tissue scattering, as well as fiber optic delivery systems used in many experiments rapidly degrade coherency. Thus any effects produced by low-energy lasers may be due to the effects of light in general and not to the unique properties of lasers." This view is not difficult to accept when it is remembered that wave-length dependent photo biochemical reactions occur throughout nature and are involved in such things as vision, photosynthesis, tanning and Vitamin D metabolism. In this view, laser therapy is really a form of light therapy, and lasers are important in that they are convenient sources of intense light at wavelengths that stimulate specific physiological functions (Lasers in Surgery and Medicine 9:1-5, Mayo Clinic, Rochester, Minnesota, 1989).