Tendinopathy: The Role of Polarised Polychromatic Non-Coherent Light Commonly called Bioptron Light

Commonly called Bioptron Light Michos Ioannis1, Talias Michalis2, Lamnisos Dimitrios3, Dimopoulos Christos4 and Stasinopoulos Dimitrios3 1Department of Computer Science and Engineering, School of Sciences, European University Cyprus, Cyprus 2Department of Health Economics and Statistics, Open University of Cyprus, Cyprus 3Department of Health Sciences, School of Sciences, European University Cyprus, Cyprus 4Department of Computer Science and Engineering, School of Sciences, European University Cyprus, Cyprus


Introduction
Low Power Laser Light (LPLL) is a commonly used light-therapy modality among physiotherapists for the management of common musculoskeletal disorders such as tendinopathies [1]. The effect of LPLL on wound healing has been investigated in many studies during the last two decades with conflicting results [2]. Polarised polychromatic non-coherent light (Bioptron light) is another form of light therapy that is commonly used to treat wound healing in dermatology and plastic surgery [3][4][5]. Manufacturers claim that Bioptron light can be used in the treatment of common musculoskeletal disorders such as tendinopathies but experimental support is lacking [6][7][8][9]. Table 1 Manufacturer's explanation in the characteristic of polarized, polychromatic non-coherent light (Bioptron light).

Polarisation
Its waves move on parallel planes. In this device polarization reaches a degree of approximately 95%, which narrows and concentrates the beam.

Polychromy
Polychromatic light contains a wide range of wavelengths, including visible light and a part of infrared range. The wavelength of this device's light ranges from 480 nm to 3400 nm. This electromagnetic spectrum does not contain ultraviolet radiation.

Incoherency
This device's light is incoherent or out of phase light. This means the light waves are not synchronized.
Available literature is predominately in the form of manufacturers pamphlets [10]. Polarisation seems to be the most important characteristic of Bioptron light (Table 1) because the Bioptron light owes its proposed mode of action in this characteristic. LPLL and Bioptron light differ in their characteristics of radiation (Table 2). Three devices are commercially available to deliver Bioptron light: (i) the Bioptron 2, (ii) the Bioptron Pro and (iii) the Bioptron Compact III [1]. According to the manufacturer's user guide, these three devices do not differ in output characteristics [11]. However, according to experts in dermatology plastic surgery [3][4][5] and physiotherapy [6][7][8][9], the Bioptron 2 seems to be the most commonly used device in practice to deliver Bioptron light. Bioptron 2 (Figure 1) is a product from Harrier Inc. USA and was developed in Switzerland. The emission of light may be administered in one-minute steps and controlled by an integrated soft-start/soft-stop electronic switch. When the treatment with Bioptron 2 is over, there is a characteristic sound (beep tone). The output characteristics of Bioptron 2, according to the manufacturers' user guide [10], are: light wavelength=480-3400 nm; degree of polarization=95%; specific power density=40 mW/cm 2 ; energy density=2.4 J/cm 2 . Bioptron 2 is approved by the FDA (USA), TGA Australia, EEC and carries an ISO 9001 certificate and EN 46001 as a patented medicallyapproved product. Manufacturer literature recommends that the Bioptron 2 device should be used in practice as follows [10]: The probe of Bioptron 2 is held at a 90° angle (perpendicular) 5-10 cm above the clean bare skin of the "injured" site as this is claimed to achieve maximal penetration of light. The regimen is six minutes of stimulation for at least three times per week for four weeks. Following this protocol, the Bioptron light was found to be an effective treatment for patients with deep dermal burns [3,4] and ulcers [5]. However, there are a few studies to find out the effectiveness of this protocol in common musculoskeletal injuries such as tendinopathies [6][7][8][9].
The manufacturer claims that there are no side effects for the use of Bioptron light because there is no ultra-violet light in the Bioptron spectrum so there is no tanning or heat effect on the skin [10]. No reports of adverse effects were found in conducted trials [3][4][5][6][7][8][9]. Manufacturers also claim that Bioptron light is not harmful to the eyes, or to pregnant women or to patients with pacemakers [10]. No prophylactic measures for both, therapists and patients, were taken in conducted trials [3][4][5][6][7][8][9]. In addition, pregnant women and patients with pacemakers were not excluded from the trials [3][4][5][6][7][8][9]. Finally, the polarised polychromatic non-coherent light (Bioptron light) cannot cause cancer because it is known that the dangerous wavelength of light is below 250 nm and the wavelength of Bioptron light is outside of this range (480-3400 nm) [10]. The lack of side effects and contraindications of the Bioptron light is supported by the conducted trials [3][4][5][6][7][8][9] and confirmed by the approval of the FDA (USA), TGA Australia, EEC, the ISO 9001 certificate and EN 46001 as a patented medically-approved product.
LPLL has a biostimulating effect [11]. Biostimulation is the reactivation of cell functions that allows regenerative processes to take place again [3]. This effect is directed to those cells that have been damaged or do not function efficiently any more [4]. A considerable amount of research has been performed to determine which of LPLL characteristics was the most important for the biostimulation effect [11][12][13][14]. Several different LPLL with varying monochromatic outputs were equally successful, showing that the wavelength played no role in the healing effects [11,12]. Coherent (in-phase) and incoherent (out of phase) light can cause the same biostimulative effects [14]. Polarisation appears to be the key factor in biostimulation [13,15]. The Bioptron light is a truly polarised light that could induce biostimulative effects in living cells similar to LPLL. The way that Bioptron light obtains biostimulative effects is not known and is based on a variety of proposed mechanisms. Both parts, visible and infrared, of the electromagnetic spectrum of Bioptron light, can explain these mechanisms. These lead to the same final photoresponse, but start the cascade of metabolic events at different cellular levels that assist tissue healing.
One proposed mechanism of action of biostimulation is the absorption of visible light energy by the mitochondria [16]. This may cause a chain of molecular events leading to an increase in cell energy and activation of nucleic acid synthesis, which is essential for tissue repair [2].
The second mechanism is obtained by the infrared portion of the light spectrum [2]. In a hypothetical physical model for biostimulation, the cell membrane was stated to be the site of stimulation [15]. In this hypothesis the Bioptron light interacts with the polar heads of the lipid double layer of the cell membrane in which the biologically active proteins are incorporated. Due to the interaction with Bioptron light, structural changes may occur to give the membrane a reordered distribution of the surface changes and to modify the lipid protein connections. This conformation change may influence the cellular processes connected with the cell membrane: receptor function, energy production, immune responses and enzyme reactions [15].
Different biological effects have been reported after polarised light radiation, including the stimulation of cell proliferation (especially in fibroblasts), the release of growth factors and the enhancement of collagen synthesis [13,15,17,18]. It can be suggested that the tensile strength of tendons can be improved indirectly through the previously reported observations.
Another mechanism that might be responsible for Bioptron light therapy's therapeutic effect is the local peripheral vasodilations, which improve blood flow and the delivery of oxygen to the soft tissue area, facilitating the transport of nutrients needed for soft tissue healing [2].
More research is needed to find out if the bioptron light is an important factor in the management of tendinopathies.