During tissue damage, cellular integrity and function is compromised. Without a means to reverse or ameliorate such damage on a cellular level, such cells will either undergo apoptosis or necrosis. The use of light therapy in wound healing is not a new concept. NASA has been working on the use of LED–based light therapy unit for use in wound healing for more than a decade. Their research came about due to the effects noted when coherent light of a specific wavelength was shown to accelerate plant growth. Due to insufficient levels of wound healing taking place in astronauts in zero-gravity conditions, they investigated the use of such light therapy modules in wound healing, as sustaining a wound in space could seriously jeopardize a mission.
This research has continued and the remarkable effects of light therapy on wound healing have been the subject of numerous academic papers in peer reviewed journals. Numerous conditions have been treated using NASA-based LED arrays and the list of treatable conditions, and the parameters necessary to treat them, is growing steadily. However, a major drawback of the NASA units (and all other existing light therapy units) is that they are large, expensive, and very complex to use. The reason for this is that they allow a clinician to adjust numerous parameters for each condition, including beam strength, frequency, duration, and so forth. Reading up on the conditions for each type of wound and treating such conditions using currents systems is a highly specialized operation and light therapy to date can only be administered by sophisticated users having an intimate knowledge of light therapy.
We have now developed and patented a revolutionary new light therapy device to address the shortcomings of other systems currently available. The Photizo device incorporates built-in protocols for the five most general conditions treatable by light therapy. Accordingly, all the parameters necessary to treat, for example, a chronic wound, or an acute wound, have been incorporated in a single protocol button – merely by pressing the appropriate button, the whole protocol is run to treat the appropriate condition. As laser-based therapy has been used by Physiotherapists and cosmeticians for many years, many questions have been asked if this form of treatment is effective in treating pathological conditions. Leading research has shown that laser and LED-based light therapy have the same effect in tissue. Current opinion is that laser and light therapy machines are just convenient devices for delivering a certain wavelength and it is the wavelength that causes the effect and not the light-emitting device that is being used. However, LED-based arrays are currently the probes of choice, due to their lower cost, less maintenance being required, and being more robust when compared to laser-based units.
The Photizo device makes use of a 630nm (150mW probe) and optional 625nm and 850nm (1200mW probe) coherent light beam produced by a high intensity LED array. This ensures that all light is within 5% of the required wavelength, and is a major distinguishing factor between the Photizo device and other supposed light therapy devices. The Photizo device is manufactured according to ISO9000 standards and has extensive product backup and warranty maintenance.
Before commencing with the effects and benefits of light therapy, it may be useful to provide a quick overview of processes occurring in diseased or injured cells.
Cellular processes in injured cells
There are 4 intracellular systems that are particularly vulnerable:
- Aerobic respiration and the production of ATP;
- The maintenance of cell membrane integrity;
- The synthesis of new proteins and enzymes involved in cell repair; and
- The maintenance of the integrity of DNA synthesis and repair.
There are also several biochemical processes that mediate cellular injury:
- ATP depletion
- Oxygen-derived free radicals
- Loss of calcium homeostasis
- The maintenance of cell membrane integrity
- Irreversible mitochondrial damage
Current research shows that light therapy is active in ameliorating most of these processes to enhance cell survival and recuperation.
How does photon/light therapy work?
Until quite recently, it was uncertain why such striking results had been attained using light therapy units. However, research in the past 5 to 8 years has highlighted the intracellular mechanisms which are involved in and stimulated by LED-based light therapy. Microarray studies have shown, on a molecular basis, which genes are up regulated when treating cells with LED-based coherent light. In addition, biochemical studies have shown that the electron transport pathway in mitochondria is up regulated, thereby providing the cells with oxygen and ATP from inside. This occurs by exciting the cytochrome b structure, which donates more electrons to the electron transport chain, resulting in an increase of ATP synthesis.
The increase in ATP serves to power the cell from the inside following injury, assisting in reversing cellular degradation, thereby assisting in tissue recovery and allowing tissues to heal faster.
This means that there are two principal regulation paths by which light irradiation works:
- The first is the connection between the light activated redox functions of the mitochondria, changes in the redox state of the cytoplasm, the depolarization of the cellular membrane and the raise of intracellular pH (alkalization of the cytoplasm).
- The second is the photoacceptor control over the level of intracellular ATP. (Even small changes in the ATP level can alter the cellular metabolism significantly).
If light is administered at the correct dose, certain cell functions are stimulated (photoresponse), and this is particularly evident if the cell and tissue in question have impaired function. A cell whose overall redox potential (pH and oxygen status) is shifted to a reduced state, is more sensitive to irradiation. It is known that chromophores (located in the mitochondrion) in the form of cytochrome b act as a photo acceptors to absorb specific wavelengths, which lead to a photoresponse.
Primary cellular reactions to light therapy:
- Small amounts of singlet oxygen, (one oxygen molecule) build up when tissue is irradiated. Singlet oxygen is a “free radical” which itself influences the formation of ATP, which constitutes the cell’s fuel and energy store.
- It has been observed that the calcium ion balance in the cell is affected.
- It has been demonstrated that irradiation with light influences the oxidative processes in the cell (suggested that cytochrome, a respiratory chain component is also an important photoacceptor).
This leads to a number of secondary effects which have been studied and measured in various contexts:
- Increased cellular metabolism
- Increased collagen synthesis in fibroblasts
- Increased action potential of nerve cells
- Effects on the immune system
- Increased new formation of capillaries by the release of growth factors
- Increased activity of leukocytes
- Transformation of fibroblasts to myo-fibroblasts
The healing process and how light therapy assists in these processes
Following trauma, blood, cellular fluids and waste products block or inhibit the entrance of oxygen and nutrients necessary for proper functioning of the cell, and disposal of waste products is impaired. If the cell has the necessary energy, nutrients and oxygen, the cell can repair itself. If the necessary elements are compromised or not available there is a “point of no return” and the cell starts the process of dying.
Repair mechanisms start clearing the area by disposal via the lymph system, phagocytosis and the blood system. This is done by increasing vascularity, lymphatic system activity and phagocytosis. Once this process is completed the tissue repair and/or regeneration can start.
The next step is to once again increase blood supply, release of ATP, collagen production, RNA and DNA synthesis, fibroblastic activity and an increase in tissue granulation and connective tissue projections. When all these processes are done, healing is completed.
Effects of light therapy
Increases the formation of new capillaries to replace damaged ones. This speeds up the healing process by carrying more oxygen and nutrients needed for healing. Accelerates waste disposal.
Stimulation and regulation of collagen production
Collagen is the most essential protein used to repair damaged tissues, and to replace old tissues. By increasing collagen production less scar tissue is formed.
Stimulate the release of ATP
ATP is the major carrier of energy to the cells. An increase in ATP allows the cells to accept nutrients faster and to dispose of waste products by increasing the energy levels in the cell. ATP provides the chemical energy that drives the chemical reactions of the cell.
Increase the lymphatic system activity
Edema has two components e.g. a liquid part which can be evacuated by the blood system and a second proteinaceous component which is comprised of proteins which have to be evacuated by the lymphatic system. Research has shown that the lymph vessel diameter and the flow of the lymphatic system can be doubled with the use of light therapy. The venous and arterial diameters can also be increased. This means that both parts of edema can be evacuated faster to reduce swelling.
Activation and upregulation of genes involved in cellular repair
This helps damages cells to be replaced promptly.
Reduced excitability of the nervous tissue
The photons of light therapy enter the body as negative ions. This results in an influx of positively charged ions like calcium among others to the area being treated. These ions assist in reducing the excitability of nerves, thereby relieving pain. Secretion of endomorphins and serotonin secretion also reduce pain.
Stimulation of fibroblastic activity
Fibroblasts are present in connective tissue and are capable of forming collagen fibres, which essential for tissue repair.
Increase in phagocytosis
Phagocytosis is the scavenging process for ingesting dead or degenerated cells for the purpose of clean up. This is most important in the destruction of the infection and this process must be completed before the healing process can start.
Induce a thermal-like effect in the tissue
Light therapy raises the temperature of the cells although there is no heat generated produced from the diode it selves. This is an important distinction between LED-based units and other light-based products – the increase in blood flow and vascularity are NOT due to heating by the probe – the probe stays cool at all times.
Stimulates tissue granulation and connective tissue projections
Granulation and connective tissue projections are part of the healing process of wounds, ulcers or inflamed tissue.
Response in patients
Patients generally experience the following:
- Dramatic reduction of swelling in the affected area
- Pain relief
- Less scar formation
- Rapid healing
- Stimulation of the immune system, thereby accelerating the antibody complement pathway
Benefits of light therapy in wound healing
- Reviving damaged cells – stimulation of repair processes (if treated in 4-6 hours of injury)
- Faster onset of granulation
- Faster wound closure
- Less risk of infection
- Less pain and swelling
- Stimulation and regulation of collagen tissue
- Securing successful skin grafts – this is an especially useful benefit.
The big question: Treatment dose
This is a very complicated issue. Doses that are too low will result in no, or only a weak effect. If a dose above the highest one suitable is administered, weaker or no biological effects will result, and even greater doses will effect an inhibiting result.
The correct dose and treatment interval differ on whether treating “open cells” like wounds, whether the condition in the tissues are acute or chronic, or whether one wishes to treat pain or achieve a more long term healing effect. Doses do not have to be perfect to produce a good biological response. A general guideline for a treatment dose is to set the dose in a “therapeutic window” (where a photoresponse will take effect) of 2 -10 Joule/cm2.
Important information about light therapy devices
What is the wavelength of the probe?
Wavelengths of 600 – 690 nm lie in the infra-red visible
Range and are useful in effecting tissue repair.
What is the effective power output of the probe?
The output power is important to know because it determines the time spent in delivering the effective dose. For example: a continuous wave, 100mW probe will deliver 1 Joule in 19 seconds, while a 50mW probe will deliver 1 Joule in 38 seconds.
Is the light continuous or pulsed?
Pulsed (e.g. duty cycle 50/50) means an on/off cycle which effectively cuts the output power in half – doses have to be increase accordingly.
Interesting points about penetration
- Different tissue types absorb light to different degrees and different wavelengths have different penetration patterns, thus affecting penetration depth.
- Dirty and dark skin reduces penetration.
- Highly vascularised tissue absorbs more light than less vascularised tissues.
- Haemoglobin in the blood is responsible for most of the absorption of light, so when you press lightly with the probe against the skin the mechanical removal of blood greatly increases the penetration depth of the light.
- Bone absorbs light.
- “Penetration depth” is the depth where 60% of the given dose is still present in the tissues.
- Treating in contact with the skin results in less refraction of the light.