Laser Therapy is a form of phototherapy which involves the application of monochromatic light over biological tissue to elicit a biomodulative effect within that tissue.
- Low-level Laser Therapy (LLLT) – the most widely-used name given to this form of photobiomodulation – can have both a photobiostimulative effect and a photobioinhibitive effect within the irradiated tissue – each of which can be used in a number of therapeutic applications.
- LLLT is gaining increasing acceptance in conventional medical, physiotherapy, acupuncture, dental, and veterinary practice – and refers to the “reaction between laser and the irradiated biological tissue” (Baxter, 1994).
- LLLT is a complementary form of treatment and, therefore, is not intended to replace other electrotherapeutic modalities, such as ultrasound, interferential therapy, and magnetic therapy. In a number of therapeutic applications, however, LLLT has been rated more highly in its effectiveness than these other modalities (Baxter et al, 1991).
Low-Level Laser Therapy
Laser Therapy works on the principle of inducing a biological response through energy transfer, in that the photonic energy delivered into the tissue by the laser modulates the biological processes within that tissue, and those within the biological system of which that tissue is a part. The Arndt-Schultz Law of Biomodulation infers that low dosages of photonic energy will stimulate those biological processes, and higher dosages will inhibit them.
The wavelength at which the laser emits determines the effective depth of penetration, within the tissue, of the laser energy delivered. Far-red to infra-red wavelengths (longer than 800nm) will penetrate deeper, and so are indicated for deeper acupuncture points and trigger points, and deeper tissue injuries. Visible red wavelengths (shorter than 800nm) do not penetrate as far, and are therefore more applicable to superficial tissue and treatment points. Photons emitted at shorter wavelengths do, however, have greater energy/mass which is measured in electron-volts (eV).
In clinical applications the effects of Visible Red laser are of use in, but not limited to, the treatment of open and post-operative wounds, decubitus & venous ulcers, acne, and other dermatological conditions. Visible Red laser has also been effective in the tonification and sedation of superficial acupuncture points.
The therapeutic effects of Visible Red laser are, however, also elicited by Infra-Red wavelengths.
Clinical Uses of LLLT
There are a number of potential clinical uses for LLLT, such as those in medical, dental, podiatric, chiropractic, osteopathic, and cosmetic applications. Some of the most popular applications of LLLT currently, however, are in physiotherapy, veterinary, and acupuncture practice.
The portability and diversity of battery and mains-powered diode laser systems allows treatment to be carried out in various clinical, hospital, and field locations. This opens up possibilities for the immediate (and thereby more effective) and on-going treatment of sporting and athletic injuries, such as muscle tears, haematomas and tendinopathies Due to its pain-relieving and wound-healing properties, LLLT has many uses in hospitals and aged-care homes, such as for the treatment of pressure sores in bed-ridden patients, and for enhanced post-operative wound healing and pain relief. The effect of LLLT is such that it can accelerate remodelling of scar tissue, and “give a more cosmetically-acceptable result” (Baxter, 1994) to post-operative scarring.
Trelles et al (1987) reviewed the use of local irradiation with Low-Level Laser in therapy. The stimulus was applied mainly to local lesions to elicit the following types of effect:
- biostimulatory effects in ulcers, granulomas, burns, septic wounds and trauma to superficial tissues;
- stimulation of local cell metabolism in damaged tissues in vivo and in vitro;
- stimulated activity of local tissue enzymes;
- enhanced scar formation and tissue regeneration, mitogenic activity, and osteogenic activity.
Trelles et al (1987) and Muxeneder (1987) also reviewed the effects of LLLT in vertebral pain, headaches and local immune responses. Other recorded therapeutic effects of LLLT (Illarionov et al, 1993) are:
- antineuralgic, antioedematous, antiseptic;
According to Laakso et al (1994), the “…analgesic response to phototherapy may be mediated through hormonal/opoid mechanisms…and…responses to LLLT are dose and wavelength dependent.”
Research being carried out around the world is constantly adding to the ever-expanding body of knowledge and understanding of the mechanisms and effects of LLLT.
LLLT & Physiotherapy
Electrotherapy and low-level laser are used in physiotherapy to assist in the attenuation of pain and to stimulate tissue repair. As such, their application is also bound by the Arndt-Schultz Law of Biomodulation, as described above. Thus, it can be seen that the dosage delivered by the practitioner during a laser treatment is determined by the condition being treated, and the desired therapeutic effect. For example, if the desired effect of an initial treatment is that of pain attenuation, an inhibitory dosage (8.0 to 16.0 Joules/cm2) would be indicated.
Australian research has also shown that dosages of between 0.5 and 5 Joules/cm2 (Laakso et al, 1994) applied to Myofascial Trigger Points will effect an analgesic response through the body’s hormonal/opoid mechanisms. If the desired effect is that of tissue repair, then the required dosage per treatment point will generally fall within the optimal therapeutic window between 0.5 and 5 Joules/cm2.
Available laser Output Power may range from 5mW to 500mW per laser emitter, with the higher powers indicated for larger muscle groups and treatment of the back. Near-infrared lasers penetrate further into the tissue. Multi-diode cluster probes may be effective in reducing overall treatment times where large tissue areas are to be treated. However, it must be noted that multi-diode LED and LED+Laser cluster probes often contain multiple wavelengths, which can lead to a degredation of the effectiveness of laser therapy (Karu, 1998).
Treatment will be effected by application of the laser probe to points along tendons and ligaments, and at the origins and insertions of muscles. Larger muscles can be treated by application of the laser in a grid pattern to a series of points across the body of the muscle, or by scanning or painting the laser head across the affected area.
Joint conditions, such as osteoarthritis, can be treated by applying the laser probe to a series of points along the joint line, aiming the probe tip at the articular surface where possible, and to the origins and insertions of muscles around the joint.
Open wound healing can be accelerated through laser therapy, by the application of 1-to-4 Joules/cm2 to a series of points in a 1cm square grid pattern across the surface of the wound, or by scaning or painting the wound surface with the laser.
As a gereral rule, optimal biostimulation is effected by the application of smaller dosages-per-point to more points at the treatment site.
Optimal bioinhibition is achieved through applying higher dosages-per-point, but to fewer treatment points.
Contraindications and Safety
- Irradiation Of The Eyes Class 3b lasers are potentially harmful to the retina. Although accidental retinal damage is highly unlikely, it is recommended that laser protective eyewear, with the correct filter for the wavelength and power being used, be worn.
- Pregnancy Laser is NOT contra-indicated for use over the pregnant uterus, however it should be used with caution. It is ideal as an adjunct to other modalities used for the treatment of back pain or other complaints.
- Carcinoma Do not use the laser over any known primary or secondary lesions.
- Thyroid Laser should not be used over the thyroid gland.
- Haemorrhage It is conceivable that laser-mediated vasodilatation may worsen the haemorrhage.
- Steroid Injections Patients may suffer an exacerbation of symptoms after laser therapy in conjunction with a recent steroid injection. For this reason laser should be used with caution following a steroid injection on or near the same site. We recommend one or two treatment points only at the minimum recommended dosage for that probe.
- Anti-Coagulants It is possible that probe pressure may cause slight bruising after treatment.
- Anti-Inflammatories Patients taking anti-inflammatories for acute soft tissue injuries may not respond as quickly to laser therapy as those who are not. Ideally, we would suggest a combination of ice and laser therapy without the use of an anti-inflammatory.
- Pins, Metal Plates and Plastics are Not Contraindicated Laser may be safely used over stitches, as well as pacemakers, metal implants, pins, plates and plastics.
- Tattoos and Other Pigmented Tissues Dark pigments, such as tattoos and melanin, may absorb light at the wavelengths used in laser therapy. Where probes with high power densities are in use, the absorption of laser energy by these pigments may cause localised heating, and subsequent discomfort or injury, of the irradiated tissue. We recommend conducting patch-tests on darker-pigmented tissues.
- General Hygeine Clinical hygiene standards and protocols should be applied.
- Legal and Regulatory Requirements Practitioners should be aware of local regulations governing the use of low-level laser therapy equipment.