The Light Touch

Get acquainted with laser photostimulation, because it is gaining credibility in the wound care arena.

by G. Kesava Reddy, PhD, MHA

Laser photostimulation is a noninvasive phototherapeutic physical modality in modern biology and medicine. The origin of this modality stems from natural light-used in healing for many centuries starting with the ancient Greeks and Romans who recognized the benefits of sunlight. Europeans introduced laser photostimulation more than 30 years ago, and researchers in other countries such as the Soviet Union and Australia used low intensity lasers to irradiate areas of skin and accelerate wound healing. During the past decade, the clinical application of low intensity laser photostimulation has gained widespread acceptance in Canada, Australia, and several European and Asian countries.

Laser light is generated in an organized manner, rather than the random pattern from an incandescent light bulb. But how does laser light differ from natural light? Conventional light is the visible part of the spectrum of electromagnetic radiation. It is composed of a range of colors and has a thermal effect. In contrast, the laser radiation has three distinguishing features: monochromaticity (a single, defined wavelength), coherence (the waves are in phasethe troughs and peaks of the waves coincide in time and space), and unidirectional (minimal divergence beam that is well collimated).

How does it Work?

Low intensity laser photostimulation works through a photochemical response to laser light that induces biochemical alterations in cells, leading to physiological changes. During laser application, photons enter the tissue and are absorbed in the mitochondria and cell membrane. The photonic energy converts to chemical energy in the form of adenosine triphosphate (ATP). Cell interaction with light at different wavelengths produces physiological changes, leading to alterations in cellular metabolism.

Certain chromophores like rhodopsin and porphyrins absorb light energy and cause chemical reactions in the cell, resulting in changes in the metabolic activities of the cell. These photochemical reactions between cells and light form the fundamental mechanism of modern therapeutic low-intensity laser photostimulation.

Low-intensity laser photostimulation has been applied in a variety of clinical and experimental settings over the past three decades. Claims of therapeutic benefits include accelerated wound healing, enhanced remodeling and repair of tendon injuries, pain attenuation, and immune system modulation.

Wound Treating

The idea to use lasers for wound healing arose from in-vitro studies in which fibroblasts exposed to laser photostimulation resulted faster cell proliferation than sham-irradiated cells. Mester et al revealed that a ruby laser treatment accelerated healing of mechanical wounds and burns in mice.' Other researchers investigated the healing rate of full thickness wounds when exposed to laser photostimulation. , In our recent study, we showed that laser photostimulation accelerated collagen production and quickened wound healing in diabetic rats." Similarly, using rabbit Achilles tendon models, we reported that the tissue repair process could be modulated using laser photostimulation.

Applying laser photostimulation is relatively simple. However, certain precautions should be followed to ascertain the amount of laser energy delivered to the tissues. In most cases, transparent dressing, or a clear, thin plastic sheet may he placed on the open skin wound during application.

Evidence suggests that the therapeutic effects of laser photostimulation start with the absorption of laser light by the cells. This is followed by signal transduction, amplification, and a photoresponse of several factors that are needed for wound healing or tissue repair. At the cellular level, laser photostimulation increases ATP production, mast cell recruitment and degranulation, growth factor release by macrophages, keratinocyte proliferation, collagen synthesis, and angiogenesis. At the tissue level, it accelerates the resolution of acute inflammation, which results in more rapid granulation and re-epithelialisation of the tissue-all of which helps the wound heal faster.

G. Kesava Reddy, PhD, MHA, is an associate research professor in the Department of Physical Therapy and Rehabilitation Sciences at the University of Kansas Medical Center, Kansas City, Kan. He can be reached via email: kreddy@kumc.edu.

References
1. Mester E, Spiry T, Szende 13, Tota JC. Effect of laser rays on wound healing. Am I Surg. 1971;122:532-535.
2. Abergel RP, Lyons RE, Castel JC, Dover RM, Uitto J. Biostimulation of wound healing by lasers: experimental approaches in animal models and in fibroblast cultures. / Dermatol5urg Oncol. 1987;13:127-133.
3. Lyons RE, Abergel RP, White RA, Dwyer RM, Castel JC, Uitto I. Biostimulation of wound healing in-vitro by a helium-neon laser. Ann Plast Surg. 1987;18:4750.
4. Hunter J, Leonard L, Wilson R, Snider G, Dixon J. Effects of low energy laser on wound healing in a porcine model. Lasers Surg Med. 198413:285-290.
5. Kana JS, Hutschenreiter G, Haina D, Waidelich W. Effect of low-power density laser radiation on healing of open skin wounds in rats. Arch Surg. 1981;116:293-296.
6. Reddy GK, Stehno-Bittel L, Enwemeka CS. Laser photostimulatron accelerates wound healing in diabetic rats. Wound Repair Regen. 2001;9:248-255.
7. Reddy GK, Stehno-Bittel L, Enwemeka CS. Laser photostimulation of collagen production in healing rabbit Achilles tendons. Lasers Surg Med. 1998;22:281-287.