Use current evidence to apply laser therapy for wound
healing and pain relief.
By Roberta Chow, MB BS (Hons), FRACGP, FAMAC, MApplSci (Med Acu), PhD
The field of laser therapy keeps evolving as clinicians and researchers
continue exploring potential uses and investigating the body's response
Exploring non-thermal therapeutic applications of lasers began after the
first production of a red laser from ruby crystals in 1960. Literature
spanning the last 40 years provides evidence of significant affects of
visible and infrared wavelengths on different cell types. Over time,
therapeutic applications have followed parallel courses, which include
wound healing, pain modulation and laser acupuncture, and provide insight
into the diverse clinical effects of lasers.
Low-level laser therapy (LLLT) uses light with specific characteristics-single
wavelength, coherence and parallelism-to treat medical conditions. Historically,
different terms have been used for LLLT, such as cold laser, low-power laser
therapy and photobiomodulation.
Laser devices with "low" output produce therapeutic effects by
non-thermal absorption of photons by cells. These actions are in contrast
to high-power lasers in surgery, where a focused laser beam produces intense
heat to vaporize tissue. The absorption of photons by enzymes within the
respiratory chain of mitochondria is the primary event by which the
electromagnetic energy of a laser is transduced into electrochemical and
electrophysical effects. These actions initiate a
cascade of secondary intracellular events that alter cell-specific functions,
inducing tertiary physiological changes in tissues that cause therapeutic
benefits, such as wound healing, pain relief and tissue repair.
Enhancing Wound Healing
Enhancing wound healing was one of the earliest clinical applications of
laser therapy. Endré Mester, a Hungarian physician, applied a ruby laser
to treat leg ulcers of varying etiology. His study of more than 2,000
patients with intractable ulcers demonstrated the healing effects of lasers,
especially venous ulcers, and provided the rationale for research that
followed. Many studies, including randomized controlled trials (RCTs) of
wound healing, have been performed.
Clinicians have gained some understanding of the mechanisms for laser-induced
wound healing after studying the effects of lasers on fibroblasts, macrophages
and other cells critical to tissue repair. Studies of fibroblast cultures provide
evidence that lasers absorbed by mitochondria stimulate ATP production to initiate
intracellular events, such as increased mitosis and procollagen formation.
Micro-DNA studies of laser effects on fibroblasts demonstrate up- and
down-regulation of 111 genes associated with fibroblast activation and
tissue repair.' In macrophages and neutrophils, lasers modulate several
functions, including phagocytic activity and degranulation.
Although in-vitro studies demonstrate stimulation of cell function and
RCTs show enhanced wound healing, not all clinical studies show benefits.
That leads to conflicting findings in meta-analyses.[3,4]
The intrinsic complexity of laser therapy is illustrated by these studies,
since the heterogeneity of laser parameters and wavelengths is a major
factor in the diverse outcomes. From these studies, it appears that visible
wavelengths maybe more effective than infrared wavelengths to stimulate
tissue repair. As such, the importance of appropriate laser parameters
Research into the pain modulating effects of lasers followed a path
similar to wound healing, with evidence for the efficacy of LLLT for
painful clinical conditions steadily accumulating in recent years.
Meta analyses and systematic reviews reveal that lasers can be effective
for chronic joint disorders, chronic pain, rheumatoid arthritis and neck
pain.[3,5-12] Single RCTs and published case series
for painful conditions suggest the possibility of broad clinical applications
for laser therapy.
Recent research provides an understanding of mechanisms for pain relief.
Researchers have identified anti-inflammatory effects across a range of
laser wavelengths and doses. Evidence also suggests that infrared wavelengths
may have selective, inhibitory effects on nociceptors, and block fast axonal
flow in A and C fibers and cause a reversible neural blockade.
Tissue repair can also produce long-term benefits to relieve chronic pain
conditions. Understanding how each of these effects interacts to relieve
pain is the subject of ongoing research.
Examining Laser Acupuncture
Laser stimulation of acupuncture points is a different application from
its use for wound healing and pain. In laser acupuncture, the laser
"needle" stimulates acupuncture points in the skin, comparable
to metallic needles.
This action activates acupuncture pathways from the spinal cord to the
It's essentially a neural stimulus that requires detailed knowledge of the
location of function specific, anatomically defined points. This is in contrast
to the effects of lasers in tissue repair and pain modulation, which rely on
the direct effects of a laser on targeted tissue.
In addition, there's no sensation with laser acupuncture; sensation is
thought to be a prerequisite for effective acupuncture. Unlike the
pain-relieving effects of needle acupuncture—which can be blocked by
Naloxone—laser acupuncture is only partially blocked, suggesting somewhat
The noninvasive nature of laser acupuncture is a clinical advantage because
there are no risks of skin penetration. Therefore, it's considered safe. The
evidence base is less well-developed for laser acupuncture, although it's
But it can be challenging to understand and apply current evidence. Laser
therapy has attracted controversy since its earliest clinical applications.
Aside from current evidence-based medical applications of non-thermal light
to treat neonatal bilirubinemia, psoriasis or seasonal affective disorder,
the proposal that a laser could induce significant clinical effects has
been viewed skeptically.
However, evidence supports laser-induced alterations in cell physiology
in a range of cells. At the other end of the spectrum, while the evidence
for clinical applications is more limited, several systematic literature
reviews and meta-analyses provide evidence of the benefits.
Several factors in laser therapy make clinical research and applications
intrinsically complex, which helps account for diverse findings. These
factors can be grouped into two broad categories: laser-related and
patient-related. You need to understand these categories to evaluate
the effectiveness of laser therapy.
The most important laser-related factors include: wavelength, which
can be divided into visible and infrared; output power of the laser
(from milliwatts to watts); duration of application (from seconds to
minutes); and mode of application, such as in contact with the skin or
scanned from a distance. Using a drug analogy, combinations of each of
these parameters constitute the laser "dose" while the
wavelength is considered the "class" of drug. Identifying the
optimal combination of these parameters for specific indications is
necessary to achieve the best clinical outcome.
For instance, optimal parameters have been identified to treat tendonitis
and osteoarthritis. However, these methods haven't been established for
many other conditions and RCTs fail to describe laser parameters, which
makes it difficult to assess laser "dose".
The complex interaction of laser parameters in clinical applications is
the basis for many disparate study outcomes. Patient-related factors,
which vary from person to person, result in positive responses to laser
therapy. Although they aren't clearly understood, they include the melanin
content of skin, thickness of subcutaneous fat and muscle tissue, and depth
of target tissue. Each component influences penetration of a laser
Laser therapy offers potentially important clinical advantages that make
its empirical use acceptable, even in areas where evidence is still
accumulating. The evidence for topical anti-inflammatory effects of lasers
is strong and important in an environment where the adverse effects of oral
NSAIDs are associated with high morbidity and costs.
Indeed, the demand for non-drug options is an important stimulus for
exploring the place of laser therapy for chronic conditions, such as
rheumatoid arthritis and osteoarthritis. In addition, the finding that
lasers can cause a noninvasive neural blockade has important implications
for managing a range of painful conditions. For instance, therapeutic
options for treating otonhealing ulcers are limited and lasers show
potential to offer an additional modality for stimulation of tissue
New therapeutic applications of laser therapy are being explored in
experimental models, such as peripheral nerve repair, spinal cord
regeneration, stroke and myocardial infarction. Extending research
into human clinical trials may offer new treatment options.
Understandiarg and evaluating the range and complexity of clinical
applications of laser requires high-quality research. Presently, the
low risk, coupled with demonstrated benefits in many RCTs, provide
clinicians with an opportunity to exercise clinical judgement with
But the concept of light as a therapeutic modality requires a paradigm
shift from a drug-centered medical practice. The basic science of
light-tissue interaction is becoming elucidated, which enables applications
to expand. Accepting laser therapy as a mainstream medical modality depends
on continuing research at basic science and clinical levels in order to
set the platform for a new branch of medicine.
References for "Light Years: Use current evidence to apply laser
therapy for wound healing and pain relief."
March 2007, Vol. 16, No. 3, p. 53-55
By Roberta Chow, MB BS (Hons), FRACGP, FAMAC, MApplSci (Med Acu), PhD
- Karu, T. (1999). Primary and secondary mechanisms of action of visible to near-IR radiation in cells. Journal of Photochemistry and Photobiology, 49, 1-17.
- Zhang, Y., Song, S. et al. (2003). cDNA microarray analysis of gene expression profiles in human fibroblast cells irradiated with red light. Journal of Investigative Dermatology, 120(5), 849-857.
- Enwemeka, C. S., Parker, J.C. et al. (2004). The efficacy of low-power lasers in tissue repair and pain control: a meta-analysis study. Photomedicine and Laser Surgery, 22(4), 323-329.
- Flemming, K., & Cullum, N. (1999). Laser therapy for venous leg ulcers. Cochrane Database of Systematic Reviews (No. CD001182. DOI: 10.1002/14651858.CD001182.).
- Bjordal, J., Couppe, C. et al. (2003). A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. Australian Journal of Physiotherapy, 49, 107-116.
- Brosseau, L., Robinson, V. et al. (2005). Low level laser therapy (Classes I, II and III) for treating rheumatoid arthritis. Cochrane Database of Systematic Reviews (Issue 4. No. CD002049. DOI: 10.1002/14651858.CD002049.pub2).
- Chow, R. T., & Barnsley, L. (2005). A systematic review of the literature of low-level laser therapy (LLLT) in the management of neck pain. Lasers in Surgery and Medicine, 37(1), 46-52.
- Umegaki, S., Tanaka, Y. et al. (1989). Effectiveness of low-power laser therapy on low-back pain. Double-blind comparative study to evaluate the analgesic effect of low power laser therapy on low back pain. The Clinical Report, 23, 2838-2846.
- Soriano, F., & Rios, R. (1998). Gallium arsenide laser treatment of chronic low back pain: A prospective, randomized and double blind study. Laser Therapy, 10(4), 175-180.
- Basford, J., & Sheffield, C. et al. (1999). Laser therapy: A randomised, controlled trial of the effects of low-intensity Nd:YAG laser irradiation on musculoskeletal back pain. Archives of Physical Medicine & Rehabilitation, 80(6), 647-652.
- Ozdemir, F., Birtane, M. et al. (2001). The clinical efficacy of low-power laser therapy on pain and function in cervical osteoarthritis. Clinical Rheumatology, 20(3), 181-184.
- Chow, R. T., Barnsley, L.B., et al. (2006). The effect of 300mW, 830nm laser on chronic neck pain: A double-blind, randomized, placebo-controlled study. Pain, 124, 201-210.
- Chow, R., & David, M. et al. (2007). 830-nm laser irradiation induces varicosity formation, reduces mitochondrial membrane potential and blocks fast axonal flow in small and medium diameter rat dorsal root ganglion neurons: implications for the analgesic effects of 830-nm laser. Journal of the Peripheral Nervous System (in press).
- Bjordal, J., & Couppe, C. et al. (2001). Low-level laser therapy for tendinopathy: Evidence of a dose-response pattern. Physical Therapy Reviews, 6, 91-99.
Roberta Chow, MB BS (Hons), FRACGP, FAMAC, MApplSci (Med Acu), PhD, is a general practitioner with a special interest in pain management using laser therapy. She recently completed her PhD at the University of Sydney in Australia, after studying the effects of laser therapy on neck pain and exploring possible mechanisms of pain relief.
Originally published in Advance for Directors in Rehabilitation - March 1, 2007