Medical laser apparatus used in the field of medicine and low-power laser treatment have been surveyed for last ten years. From a viewpoint of science and engineering, the effect of low-power laser irradiation has been discussed by considering the Honda-Fujishima effect in electrochemical photolysis of water, synergistic effect in surface phenomena related to plasrna-wall interaction and hypersonic effect in audio engineering.

View full abstract

The present review summarizes the cytological effects of low power laser irradiation. The most important effect is cell proliferation. The cytological effects depend on the cell cycle at a point of irradiation time6 and physiological state of cell. Dose and wavelength of irradiation determine the effects, however the high spatial coherence, one of the unique characters of laser, may not be related. Irradiated light may be primarily absorbed in the respiratory chain components (e. g. cytochrome, flavin) on the mitochondria, and then the activated components will promote the electron transport and the ATP synthesis. An irradiation of excessive dose will damage the inner-membrane of mitochondria with the light-generated free radicals, and then inhibit the cell proliferation.

View full abstract

Low reactive-level laser therapy (LLLT) has been used for patients with various chronic pain syndromes. The efficacy of LLLT in pain attenuation and its mechanisms have been reported by both clinical and experimental works. Including laser irradiation near on the stellate ganglion, repeated sessions of LLLT should be necessary for satisfactory pain attenuation. Although LLLT is noninvasive and safe with almost no adverse effects, its strict indication and adequate duration of therapy should be considered.

View full abstract

Although many clinical studies have tested usefulness of low power laser (LPL) irradiation for the wound healing, the mechanism of the effects by LPL irradiation has not been fully elucidated. The present study demonstrated that the enhanced LPL irradiation effect to the procollagen production was consistently observed in the serum-starved medium, not in the FCS-contained medium. These results suggested that some factors in FCS might interfere with LPL irradiation onto procollagen synthesis. This view is supported by the fact that LPL irradiation was much more effective in intractable ulcers and bloodless wounds, which could be lack in FCS. The LPL irradiation effect was not blocked by dexamethasone but methylene blue. It seems probable that the LPL enhanced effects to the procollagen product of the fibroblast might be occurred at the translational level not at the pretranslational level of the mRNA synthesis and cGMP might be involved in the enhanced effect of the procollagen synthesis in fibroblast.
In vivo study, the effect of the low power laser on the inflammatory stage of wound healing was investigated using delayed wound healing animal model. Round open wounds were made on the bilateral backs of doxorubicin treated pigs. Five-days LPL irradiation (for 3 min/day) suppressed the excess production of fibronectin caused by doxorubicin and also suppressed the number of the infiltrated inflammatory cells. Effectiveness of the LPL was also observed to keratinization. These results suggest that LPL may have immunosuppressive effect and also stimulate on delayed wound healing.

View full abstract

Low power output laser is applied in the treatment of pain and paralyses with the expectation of some reaction in living such as the improvement of peripheral circulatory disturbances and anagenesis. In this paper, the usefulness of the treatment with the low power Nd: YAG laser irradiation is examined in 30 cases with peripheral facial palsy. The irradiation output of the low power Nd: YAG laser device was set at 300mW. The irradiation was given to the disturbed side of the stellate ganglion and the stylomastoid foramen for 10-15 minutes per exposure and 1-2 times a week. As for the effectiveness of the treatment, 11 cases (36.7%) were assessed as markedly effective, 16 (53.3%) as effective, and 3 (10.0%) as ineffective; the over all effective rate was 90.0%. Since the low power Nd: YAG laser treatment was simpler than the stellate ganglion block and non-invasive, it is expected to be used widely in the future.

View full abstract

Extracorporeal circulation (ECC) using a pump-oxygenator is indispensable support for cardiovascular surgery. However, problems remain because of erythrocytic damage. So we studied the protective effect of low power He-Ne laser as a novel means of alleviating the erythrocytic damage caused by pump-oxygenator, in the absence of drug administration.
Experiments were using a hollow-fiber type membrane oxygenator, connected to a closed circuit filled with a human erythrocyte suspension (leucocytes and plasma were excluded). One of the circuits was used for laser irradiated group and the other for control. Two circuits were inserted into one double roller pump, and experienced same time, using the same sample. The laser group demonstrated significantly higher erythrocyte deformability and erythrocyte ATP levels, and lower free hemoglobin and lipid peroxide levels. A laser output power of 8.5mW was most effective in protecting the erythrocytes. Furthermore, in subsequent morphological observations using a scanning electron microscope, there were fewer spinous erythrocytes and more normal discocytes in the laser group when compared to the control group. This finding was consistent with the results of physiological and biochemical tests.
Low power He-Ne laser irradiation was shown to protect human erythrocytes from the damage caused by experimental pump-oxygenator, and the clinical application of low power He-Ne laser irradiation for ECC during cardiovascular surgery might be indicated.

View full abstract