Mickey Mouse science? Is LPT really ineffective for wrist pain?

By Jan Tunér

“Extraordinary Claims Require Extraordinary Evidence”.  The authors of a study by Petrofskya et al. [1] make an extraordinary claim by boldly stating that Low Level Laser Therapy (LLLT) for patients with wrist pain is no more effective than any incoherent light source. What is their extraordinary evidence? This study is extremely flawed. The scientific flaws can be summarized as follows:

Three of the four light sources used are LEDs and not lasers. A search on the web sites of the reported companies gives no clue to any production of lasers. This mistake alone disqualifies the study from being published in a scientific journal. Lasers and LEDs are not exchangeable light sources in biomedicine.

No information of power of the light sources is given, nor applied energy (Joule) or energy density (J/cm2). This is the very minimal information required for a LLLT study. A decent study would also report spot size and power density.

The discussion about the penetration properties of laser light is based upon a paper from 1995. Infrared laser light can easily penetrate the skin barrier, with a peak around 810 nm [1, 2]. But indeed, red, blue and violet light has a poor penetration and red lasers are mainly indicated for superficial structures.

There is currently hardly any scientific background for the use of blue or ultraviolet lasers for LLLT. The depth of penetration is very poor and even if a laser had been used (and it was not), there would probably be no effect on a painful condition.

In the discussion, the authors elaborate on then various frequencies in LLLT. What they actually mean is wavelength. “Frequency”, although the same as wavelength in physics is avoided in LLLT discussions since it is more widely used to indicate “pulse repetition rate”.

The authors’ knowledge about the scientific literature is scant. 6 out of the 12 LLLT references are from the period 1989-1998. Therapeutic lasers in this period were often quite low powered and applied energies suboptimal. In the year 2000 PubMed had some 20 listings about LLLT. From that date, 3700 new papers have been added.

The authors have misinterpreted the reference 16. This paper does not report LLLT as ineffective but points out reasons for failures in LLLT research, such as in the very present study [4].

When LLLT studies are to be evaluated, it is crucial to include and evaluate the laser parameters. There is a “dosage window”. Staying below or above this window results in negative outcomes [5]. The authors have in the first place not reported their own parameters, let alone evaluated those of the quoted studies.

Summing up, the authors have grossly failed to present their extraordinary evidence for their extraordinary claim.

[NB:  A letter to this effect was submitted in mid-October 2014 to the Editors of the Journal in which this paper was published. As yet, however, no response has been received.]


  1. Jerrold S. Petrofskya et al. The effects of low-level laser therapy in patients with wrist pain: is this Mickey Mouse science? Phys Ther Rehabil Sci. 2287-7576, 2014, 3 (1), 1-6.
  2. Kolárová H, Ditrichová D, Wagner J. Penetration of the laser light into the skin in vitro. Laser Surg Med 1999; 24: 231-5.
  3. Joensen J, Ovsthus K, Reed R K, Hummelsund S, Iversen V V, Lopes-Martins R A, Bjordal J M. Skin Penetration Time-Profiles for Continuous 810 nm and Superpulsed 904 nm Lasers in a Rat Model Photomed Laser Surg. 2012; 30:688-94.
  4. 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; 16:245-8.
  5. http://waltza.co.za/documentation-links/recommendations/