Jan Tunér DDS, Swedish Laser-Medical Society

Low level laser therapy (LLLT) has been practiced for more than 30 years but there are still many sceptics, claiming that there is no scientific documentation for this kind of treatment. While this was partly true in the 80s and early 90s, it is no longer the case and critics ought to familiarize themselves with modern research.

Since the first paper was published in 1967, some 2500 reports have been published worldwide. More than 100 positive double blind studies (1) are there for those who want to learn about LLLT. In dentistry alone (2), some 275 papers have been published. 85 institutions in 37 countries are represented, which illustrates the world-wide interest in LLLT. Of these 275 papers more than 90% report on positive effects on LLLT. 

Critics often refer to studies with a negative outcome. This is a fair point, but a large part of these studies contains flaws, and after a serious scrutiny it is obvious that they cannot be used (3). Typical flaws are extremely low dose, ineffective treatment technique, miscalculation of the dose, unsuitable inclusion criteria and low power density. A combined knowledge about laser physics, medicine and low level laser therapy clinic seems to be necessary to carry out a proper study. Some negative studies are impeccable and should be taken quite seriously. All parameters cannot be effective and we learn from the failures.

The positive double blind studies are unfortunately not too easy to find. Among the 100 selected for evaluation, only 28 could be found on Medline. Many of them have been published in regional or national publications, not indexed on Medline. This is a relative quality marker. Only 57 had been published in journals, 33 were abstracts and 10 could only be found as references. An overall rating on a scale 0-5 was 3.6 for the published papers and 3.0 for the 33 abstracts and the 57 published papers together. No less that 19 indications are found in these papers; pain, arthritis and wound healing being the most prominent ones. It is difficult to accept that one kind of therapy can influence so many conditions. However, if the general influence of light on biological systems is considered, it is more understandable.

Several meta analyses of the available literature have been published. Some of these have not accounted for the flaws in the studies, only the study design. More recent US university meta analyses on wound healing (4), tissue regeneration and pain (5) have a very significant outcome.

It is a reasonable claim to say that LLLT is well documented, certainly better documented that the uncontroversial ultra sound therapy. So why the controversy? There are several reasons. To begin with, industry supplied inferior lasers in the 80ies. While the LLLT pioneer Endre Mester (using 25 mW ruby- and helium-neon lasers) recommended 1.5 J/cm2 as a suitable dose for wound healing, the industry produced lasers in the range of fractions of a mW to a couple of mW. Even researchers tried to use those midget lasers and often failed. The advent of stronger lasers at reasonable prices have improved the situation considerably. It is now well accepted that doses around 4 J/cm2 are a good standard for wound healing and that pain treatment requires higher doses. These doses were not practically reachable with the lasers of the 80s. It is also logical that the enthusiastic reports from clinicians differed from those of some researchers. To simplify things it can be said that therapists treated sick people and researchers treated experimental conditions in healthy individuals. Further, the sensitivity for LLLT differs a lot from individual to individual and certainly many a therapist met patients who were responding even to rather low doses of laser light and were suprised at what they saw. 

In conclusion it can safely be stated that low level laser therapy is much better documented than many persons tend to beleive and that the scientific background is sound enough to say that it is a safe and effective treatment modality. However, the biological effects of laser light on various conditions are very complex and more research is needed to find out the optimal parameters.

Further information about LLLT can be found on the Internet portal "LaserWorld", www.laser.nu, which is a non-profit site sponsored by the Swedish Laser-Medical Society. 

References:

1. Tunér J. What is in the LLLT literature? In: Lasers in Medicine and Dentistry. Basic science and up-to-date clinical application of Low Energy-Level Laser Therapy, LLLT. Eds: Simunovic Z, Trobonjaca T. European Medical Laser Association, Locarno, Switzerland. 2000, pp. 217-226. ISBN 953-6059-30-4.
   Tunér J, Hode L. 100 double blind studies - enough or too little? SPIE Proc., in press.
   
2. Tunér J, Hode L. Low Level Laser Therapy, clinical practice and scientific background. Prima Books in Sweden, 1999. ISBN 91-630-7616-0.
   
3. Tunér J, Hode L. It's all in the parameters: a critical analysis of some well-known negative studies on Low Level Laser Therapy. J Clin Laser Med Surg. 1998; 16 (5): 245-248.
   
4. Bounkeo J M et al. The efficacy of laser therapy in the treatment of wounds: a meta-analysis of the literature. Proc. Third World Congress of the World Association for Laser Therapy, Athens, Greece, May 10-13 2000, p. 79.
   
5. Parker J et al. The effects of laser therapy on tissue repair and pain control: a meta-analysis of the literature. Proc. Third World Congress of the World Association for Laser Therapy, Athens, Greece, May 10-13 2000, p. 77.