Since then, a number of light devices have been cleared by the FDA, starting the flourishing of a whole new era in electrotherapy. However, with this new freedom for chiropractors to use lasers have come a slew of claims from some manufacturers that are confusing to the chiropractic consumer. In this article, I attempt to clear up some of this intellectual murkiness and help doctors of chiropractic better understand laser therapy, starting with the basics.
What Is a Laser?
A laser is simply a machine that takes electricity and produces photons - tiny primary light particles that are forced into a collimated, coherent stream. "Collimated" means that the light beam is focused into a very narrow column and not allowed to spread. "Coherence" means that the waves of light are in phase. By contrast, the soft, diffuse emissions of a light bulb are neither collimated nor coherent.
Laser Power
The power of a light device is expressed in milliwatts (mW); the number of milliwatts per second is called a joule. The joule is the most commonly used clinical term to describe the output of a laser treatment, because it combines the amount of light emission plus the time. The devices that apply to this discussion are generally in the group called Class 3B Lasers. This includes most lasers between 5 and 500 mW. By contrast, high-powered lasers used by medical doctors for dermatology and surgery are typically between 10,000 and 25,000 mW.
In Europe and Asia, there is a clear trend among physical therapists and chiropractors to use more powerful lasers. This movement toward higher-powered devices has occurred because research indicates that treatment time is often inversely proportional to the dose. There is also some indication that very low-power lasers can be ineffective.1
At the present time, low-level lasers possessing a minimum of 500-1,000 mW are becoming more popular throughout Europe and Asia because a 1,000 mW laser can treat an area 100 times faster than a 10 mW laser. Thus, assuming the same number of joules, a 10-minute treatment with a 10 mW laser requires only about six seconds when performed with a 1,000 mW laser!
Does the Frequency Make Any Difference?
One controversial area of light therapy concerns the effectiveness of frequencies. Since light can be oscillated, like many other electrical modalities, the possibility exists that changing the beam from a nonmodulated current to a sine wave might have beneficial effects. Settings called "Rife" or "Nogier" frequencies are being used by a small group of practitioners who swear they are effective treating everything from diabetes to cancer. Although you will find vehement proponents of these specific effects of using specialized frequencies for healing, little blinded research supports these claims at the present time. However, a number of clinicians claim there is growing clinical evidence that some frequencies may be more effective than others.2
Are All Light Sources the Same?
There are two types of devices on the market that produce light: noncollimated, noncoherent LEDs (light-emitting diodes) or laser (semiconductor) diodes. Some researchers claim that lasers are more effective than LEDs.3 Other scientists emphatically state that photons are photons, in spite of the type of diode, and they all have the same clinical effect.4 We do know that both have very powerful therapeutic effects and are quite similar. The advantage of a laser is that moving the light source away from the body will not reduce the dose as much as with an LED. Also, laser light, because it is collimated and coherent, may have more momentum and the ability to create increased friction inside the body. This may have clinical benefits. The advantage of the LED is that it is less expensive and therefore can be made into big clusters or unattended pads, allowing a doctor to treat wider surface areas cost-effectively.
How About Wavelength?
Unlike an infrared lamp, a therapeutic light device is monochromatic and emits light in only one wavelength. Most therapeutic devices are in the optical window of 600-1,000 nanometers (one micron). There is some indication that 1-micron devices may have slightly deeper penetration, with the lower wavelengths being more superficial, especially when used on patients with darker skin.5 However, the penetration of these different diodes is often quite similar, and increased treatment times can make up for any variance in wavelength. The bottom line: If you are buying a laser or LED device, make sure it is within this optical window.
Enough Is Enough
Most experts agree that a treatment point or trigger point requires approximately 2-5 joules and that the maximum full-body dose is approximately 150 joules. Consequently, a 100 mW laser produces 6 joules per minute, whereas a 10 mW laser produces only .6 joules per minute.
How Do I Learn More?
In my opinion, the most informative book presently available is Laser Therapy by Dr. Jan Tuner, a world-renowned expert on low-level laser therapy. For more information on this text, visit www.thorlaser.com/usa. If you have questions about laser therapy, please feel free to contact me. I started using lasers in 1985 and can help answer any technical questions about your low-level laser.
References
- Tuner J, Hode L. It's all in the parameters: a critical analysis of some well-known negative studies on low-level laser therapy. Journal of Clinical Laser Medicine and Surgery 1998;16(5):245-48.
- Tuner J, Hode L. Laser Therapy: Clinical Practice and Scientific Background. Prima Books of Sweden, 2002.
- Bihari I, Mester A. The biostimulative effect of low-level laser therapy of longstanding crurual ulcer using HeNe laser, HeNe plus infrared lasers and non-coherent light. Laser Therapy 1989;1(2):97-102.
- Whelan H, Smits R. Effect of NASA light-emitting diode irradiation on wound healing. Journal of Clinical Laser Medicine and Surgery 2001;19(6):305-14.
- Zhao Z, Fairchild P. Dependence of light transmission through human skin on incident beam diameter at different wavelengths. SPIE 1998;3254:354-61.
Curtis Turchin, DC, MA
Woodside, California
(650) 369-3336
Dr. Curtis Turchin received his undergraduate degree in biomedical sciences from the University of Southern California, a master's in education from San Francisco State University and a doctorate in chiropractic from Palmer College. He was director of clinical sciences for the company that developed the first FDA-cleared light device, and is now president of Apollo PT Products. Dr. Turchin is the author of Light and Laser Therapy and Treating Addictions With Laser Therapy, and has authored numerous articles in research and other publications.