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Learn tips about Class IV laser therapy and other health related topics on the LightForce Therapy Lasers blog!  Check back weekly for updated posts.

FAQs About Laser Therapy Blog Header

Contributed by Mark Callanen, PT, DPT, OCS

Unlike in the movie Spinal Tap, where having an amplifier that “goes to 11” doesn’t mean it’s actually going to be louder than any other amplifier, having a laser with higher power will enable you to do things a much lower power laser will not. Looking into a Class IV laser (one that has over 0.5 W of power) is a wise investment if you are planning on putting a laser in your clinic.

The biggest challenge with low level laser therapy (LLLT), more correctly referred to as photobiomodulation therapy, is getting light energy in sufficient quantity to injured tissues. Skin does an excellent job scattering and reflecting most of the light that it is introduced to it. Additionally, melanin absorbs most of the remainder of light into the skin, leaving very little to get transmitted below skin level. When normal white light or sunshine hits the skin, very few photons get past this impressive gate keeper.

Certain wavelengths of light energy penetrate the skin better than others. Unfortunately, additional barriers exist under the skin that want to grab or reflect more of the remaining light that gets past the skin1. These include hemoglobin, oxyhemoglobin, fat, and water to name a few. Therefore, careful consideration has to be given when choosing therapeutic wavelengths to maximize a laser’s effectiveness on influencing the healing process of muscle, nerve, tendon, and other connective tissue.

Wavelengths around the near infrared portion of the spectrum (800 to 1000 nm) are ideal for exciting chromophores in tissue under the skin and not getting absorbed by the obstacles previously listed2. Even when using ideal wavelengths, there is a significant loss of light energy from the surface to only a few centimeters below the skin. Rabbit studies have confirmed that only 2-3% of surface light reached the peroneal nerve when applied on shaved skin3.

As if the natural barriers to light weren’t enough, most injuries involve dozens to hundreds of square centimeters of tissue damage. When larger areas need to be treated, even more power is needed at the surface to maintain the same therapeutic dose at depth over the entire treatment area2. Therefore, even if you are using a laser that has the appropriate wavelengths to penetrate tissue ideally, but has a very low level of overall power, you will only be able to effectively treat very small areas. Additionally, treatments may take 30 minutes or longer to get it done2!

A review of how power and time relate to the overall joules applied to an area will help clarify this problem. Laser dosage is defined as joules/cm2. It is a function of (wattage x time)/ area. If a laser has low power (wattage) and/or you need to treat a large area, these two factors can only be overcome by significantly increasing treatment time to maintain the desired dosage.

This is the plight of Class IIIb lasers and is a primary reason a lot of early laser research had underwhelming outcomes. Insufficient dosage to injured tissue will not affect significant change at the mitochondria, and the positive effects of photobiomodulation will not be realized.

Class III vs Class IV_LightForceThis concept helped influence the FDA in 2004 to accept the use of Class IV lasers for photobiomodulation. Class IV lasers start where Class IIIb leave off at 0.5W of power. This higher wattage allows for sufficient laser energy to be passed onto nerve, muscle, ligament, tendon, and/or capsular tissue in a reasonable amount of time. Normal treatment sessions range from 2-6 minutes, which is quite acceptable in a clinical setting. Higher powered lasers will also allow clinicians to have the versatility to treat injured tissue in multiple areas in a given session, which greatly improves the overall effectiveness of the laser when adding it to a plan of care.

Class IV lasers are generally more expensive than Class IIIb technology, but there is no real comparison when it comes to clinical application. “You get what you pay for” is applicable here. Other factors to consider when comparing laser products include: where the device is manufactured, warranty parameters, application heads, and what type of customer service is available to help educate your staff on how to effectively use the laser after it is purchased.

While cost is an important variable with any purchase, careful consideration should be given to these factors as well as how you intend to use the laser. Getting a device that best fits your patient population and your clinic’s budget will help create a win-win for your patients and your facility from whichever laser platform you decide to purchase.


1. Hamblin MR, Demidova TN. Mechanisms of low level light therapy. Proc. of SPIE Photonics. 2006; 6140: 614001-01-12. doi: 10.1117/12.646294
2. Chris E. Stout, Matt Kruger and Jeffrey Rogers, (Eds)- © 2011 Bentham Science Publishers Ltd. Current Perspectives in Clinical Treatment & Management in Workers’ Compensation Cases, 2011, 15: 191-201.
3. Anders JJ, Bethesda, MD. In Vitro and In Vivo Optimization of Infrared Laser Treatment for Injured Peripheral Nerves. Lasers Surg Med. 2014 Jan;46(1):34-45. doi: 10.1002/lsm.22212. Epub 2013 Dec 11.


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There is currently a lot of discussion in rehab circles surrounding the efficacy and therapeutic potential of light-based modalities. From professional sports teams to private practices, these technologies are starting to be used on a daily basis to treat injured tissue. Light-based therapy used to treat pain and inflammation can be delivered by both lasers and LEDs, and consumers often want to know the operational and therapeutic differences between them. Let’s take a look at the similarities and differences between the two.

Both laser and LED therapies rely on being able to deliver an adequate amount of energy to the target tissue in order to precipitate a photochemical process known as photobiomodulation (PBM). PBM “is a nonthermal process involving endogenous chromophores eliciting photophysical and photochemical events at various biological scales. Some processes that are impacted include, but are not limited to, the alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regeneration.”1

Both sources of light share the same mechanism of action and are both commonly generated using diode technology. When used and studied in therapeutic applications, both lasers and LEDs are often built to emit similar wavelengths, either in the red or near-infrared spectrum, and have been shown to have pain and inflammatory reduction properties.2 Significant differences between the two do exist, however; including the power generated, the specificity of wavelength, and the physical characteristics of the beam generated from the diode.

Laser light is unique, in that it is monochromatic, coherent, and collimated. These traits make it well-suited to many medical applications.3 The monochromatic, or single wavelength, beam is ideal for stimulating chromophores in biological tissue that only respond to very specific wavelengths. Coherent photons are organized where non-coherent photons are not. This property is important to minimize photon scatter as light interacts with tissue. Lastly, since injured tissue is normally deep in the body, laser’s columnated beam helps focus energy in a narrow, direct path which is ideal for treating tissues at depth.

LEDs usually emit light in a small band of wavelengths (~20 nm wide) but cannot emit a single specified wavelength (~1 nm wide). This bandwidth impacts their ability to dial in the wavelength to optimally target desired tissues. Additionally, LEDs produce neither a collimated nor coherent beam, which is less ideal when treating deeper tissues. Lastly, LED’s operate at significantly lower power (wattage) than most lasers, which impacts their ability to reach deeper tissues in smaller windows of time.

When trying to target deeper tissues, wavelength is a critical variable that can play a significant role in the light’s ability to penetrate tissue. But it is not the only determining factor in therapeutic effectiveness. Power is a second variable that also plays a large role in determining both proper use and consistency of outcomes for light-based therapies.4 Lasers are generally capable of producing much higher powers than LEDs, which significantly impacts their ability to reach deeper tissues.

This is due to the concept of therapeutic depth, which involves getting an adequate amount of photonic energy to injured tissue to have a photobiomodulation effect. Since a significant amount of light is lost as it passes through tissue, having more initial power at the surface improves the modality’s ability to provide adequate amounts of energy at depth.

For superficial uses, such wound healing5, therapeutic effects can be achieved with a minimal amount of energy applied to the surface, for which LEDs are well suited. For deeper or more wide-spread conditions, such as fibromyalgia6 or chronic low back pain7, a greater amount of energy must be delivered for a sufficient therapeutic effect to be achieved.

Knowing what types of injuries will be treated with your light-based modality will impact which device will be most beneficial to the practice. LEDs often get a lot of initial attention because they are much cheaper than laser technology. Lasers used to treat deep tissue (that offer a wider range of power), however, give providers the most flexibility in terms of treatment capabilities as they can be used to treat both superficial and deep conditions. Weighing the considerations listed above should help you make the right decision when it comes time to purchase one of these devices.


1. http://www.litecure.com/about-photobiomodulation/
2. Kim, W.-S., & Calderhead, R. G. (2011). Is light-emitting diode phototherapy (LED-LLLT) really effective? Laser Therapy, 20(3), 205–215. http://doi.org/10.5978/islsm.20.205
3. Azadgoli B, Baker RY. Laser applications in surgery. Annals of Translational Medicine. 2016;4(23):452. doi:10.21037/atm.2016.11.51.
4. Knappe, V & Frank, Frank & Rohde, Ewa. Principles of Lasers and Biophotonic Effects. Photomedicine and Laser Surgery. 2004;22: 411-7. 10.1089/pho.2004.22.411.
5. Harry T. Whelan, et al. “Effect of NASA Light-Emitting Diode Irradiation on Wound Healing .” Journal of Clinical Laser Medicine & Surgery. July 2004, 19(6): 305-314. https://doi.org/10.1089/104454701753342758
6. Panton, Lynn, et al. “Effects of Class IV Laser Therapy on Fibromyalgia Impact and Function in Women with Fibromyalgia.” The Journal of Alternative and Complementary Medicine. May 2013, 19(5): 445-452. https://doi.org/10.1089/acm.2011.0398
7. Vallone, Francesco, et al. “Effect of Diode Laser in the Treatment of Patients with Nonspecific Chronic Low Back Pain: A Randomized Controlled Trial.” Photomedicine and Laser Surgery. August 2014, 32(9): 490-494.

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FAQs About Laser Therapy Blog Header

Contributed by Mark Callanen, PT, DPT, OCS

Photobiomodulation therapy (also known as laser therapy) is a nonthermal, photochemical process that results in beneficial therapeutic outcomes, including the alleviation of pain and inflammation, immunomodulation, and promotion of wound healing and tissue regeneration. It also promotes muscle relaxation and increased local circulation. While this sounds similar to the effects of ultrasound, the two modalities are actually quite different.

Therapeutic ultrasound works by a piezoelectric effect. A vibrating crystal in the head creates cavitation in tissue via sound waves. This cavitation produced in therapeutic ultrasound machines causes friction among water molecules and in turn creates heat in the tissue. This warming effect promotes local vasodilation.

When deep tissue lasers are used, there is often minor heating at the epidermis, as melanin and hair will absorb light energy. While the minor heating can help relax muscles and decrease pain, the heat sensed at the skin is not what creates the improvements in microcirculation and local vasodilation – these effects result from a process called photobiomodulation (PBM).1,2

Local perfusion increases after specific wavelengths of light reach the inner mitochondrial membrane of injured cells and excite the chromophore Cytochrome C. When energized adequately, activated Cytochrome C oxidase frees up bound nitrous oxide (NO), which improves vasodilation in the local area and promotes healing.3 In addition to freeing up NO, there are a host of other beneficial cellular interactions that take place during photobiomodulation that positively influence the inflammatory cascade and improve tissue healing by impacting the mitochondria directly.3

The chart below shows several differences between the laser and ultrasound modalities. Given that laser’s mechanism of action impacts the metabolism of the mitochondria and ultrasound does not, the influence the two modalities has on tissue(s) is quite different.

Laser vs Ultrasound

An added benefit of PBM therapy is that it can be used over metal implants, while ultrasound cannot. Since light is simply reflected off metal, use over total joints is not a contraindication. Given laser’s ability to have positive effects on inflammation and pain, it is the ideal modality to use on post-operative total joint patients with pain and swelling.

As research continues to build and better outcomes are achieved consistently, health professionals are increasingly viewing PBM therapy as a clinical asset worth investing in. Unlike ultrasound, laser’s ability to quickly impact pain, inflammation, and tissue repair make it a very versatile modality – one that clinicians find themselves reaching for again and again. So if you are looking at bringing a modality into into your practice, take a look at deep tissue therapy lasers – the only thing you will regret is not getting one sooner.


1. Mrowiec J 1997, ‘Analgesic effect of low-power infrared laser radiation in rats’, Proc SPIE, vol. 3198,no. 83, pp. 83-89.
2. Asagai, Y. 2000, “Thermagraphic study of low level laser for acute phase injury”, Las Ther, vol 12. pp 31-33.
3. Chris E. Stout, Matt Kruger and Jeffrey Rogers, (Eds)- © 2011 Bentham Science Publishers Ltd. Current Perspectives in Clinical Treatment & Management in Workers’ Compensation Cases, 2011, 15: 191-2.


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