The effect of coherent light on the proliferation of resting and mitogen (PHA) transformed T-lymphocytes was investigated in vitro. T-cells were separated from human peripheral blood by Ficoll-Isopaque and rosetting techniques. Mitogen- and non-mitogen pulsed lymphocytes were irradiated using the following energy densities: 1.2, 3.6, 6.0, 8.4,10.8, and 13.2 J/cm². The wavelength (820 nm) and pulsing frequency (5000 Hz) were kept constant as was the power output (50 mW). Controls were sham-irradiated. Following 3 days of incubation, cell proliferation was assessed using ³H-thymidine incorporation. There was a significant stimulation of lymphocyte proliferation following exposure to 1.2 and 3.6 J/cm² in the group not treated with PHA. However, the higher energy densities of 10.8 and 13.2 J/cm² were inhibitory to T-cell proliferation. Laser irradiation following mitogen addition to T-lymphocytes had an inhibitory effect on lymphocyte proliferation in all the groups studied. The results obtained suggest that the responsiveness of T-lymphocytes to laser therapy varies according to: (1) the amplitude of energy density, and (2) the status of T-cell activation, only cells unstimulated by mitogen being capable of a positive response.

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Low incident doses of Helium-Neon (HeNe) laser therapy are routinely used in our institute as an adjunct to chemotherapy for treating cases of tuberculosis. Although the mechanism of the action of laser therapy in the treatment of this pathology is not completely clear, macrophage cells are however recognized as the key cells in treating the pathology of tuberculosis. The present study was thus designed to see the in vitro effect of laser over the macrophages. The macrophages were isolated from five healthy volunteers and five pulmonary tuberculosis (PTB) cases and cultured in microwells. The macrophages in multiple wells irradiated on third, fifth and seventh day with HeNe laser (wavelength of 632.8 nm and an output power of 3 mW ) for 10, 5 and 2 mins. The cell counts carried out on the tenth day showed that the irradiated wells had increased cell proliferation ( p < 0.01 ) than the non-irradiated wells for all exposure times, and it was optimal for the wells exposed for 5 min. Microscopic examination revealed increased cell size, with a larger nucleus and RNA content. The release of TNF- α, and granulocyte macrophage-colony stimulating factor (GM-CSF) were greater for the wells exposed to the laser. The results were similar for the macrophages from the healthy volunteers and the tuberculosis cases. Thus, the findings suggest that laser irradiation activates macrophages from healthy subjects as well as from patients suffering from PTB.

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This article presents an analysis of a number of frequently cited studies on the effects of low level laser therapy (LLLT). In many of these studies, the analysis uncovered one or more reasons for the negative findings reported, the most common being the use of extremely low doses. Other reasons included faulty inclusion criteria, inaccurate control group definition, ineffective methods of therapy, inadequate attention to systemic effects and tissue condition, and low incident power density. A weakness often encountered in these studies is their failure to provide sufficient data on laser parameters. Since negatively inclined studies such as these are often quoted as “proof” of the ineffectiveness of LLLT, it is important that they be subjected to a proper critical analysis. 1,400 articles were reviewed for this analysis, the emphasis being on double-blind studies. Of the 135 localized double-blind studies, 85 reported positive findings. Though important, the critical examination of scientific literature is decidedly unglamorous. It involves hours and days of searching through a wide variety of different sources, and by no means all information is yet available on-line. There are numerous pitfalls, too, especially for those who opt to read abstracts only - criticism of sources is impossible unless an article can be studied in its entirety. Basing an opinion from abstracts obtained from online services such as Medline is risky. In addition, only a very small number of the early LLLT research reports are available from the major databases. In the following analysis of the available literature, we have chosen to analyze those studies unable to demonstrate the effectiveness of LLLT. Although priority was given to double-blind studies, non-double-blind studies were also included in certain typical cases. Certain studies were also included merely on the grounds that they are among the most frequently cited. The 1,400 articles reviewed for this analysis are now being stored in computeried form.

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Patients of more than 60 years of age and affected by chronic low back pain were randomly assigned to two groups. Group A, consisting of 38 patients, was irradiated with a pulsed GaAs diode laser, 904 nm, pulse width 200 nsec, pulse frequency 10,000 Hz, peak power of 20 W, average power 40 mW, spot size 150 cm² in area, and an angle of divergence of 6°. The laser was applied in the point technique with a dose of 4 J/cm² per point in the area of pain. Group B, consisting of 33 patients, was treated with sham irradiation with a deactivated laser system. Neither the patient nor the operator knew to which group each patient was randomly assigned. The use of analgesic drugs and physical therapy was excluded in both groups. Ten daily consecutive sessions were carried out once per day. Pain was evaluated through an analogue and visual scale at the beginning and at the end of the treatment. Laser treatment was considered effective when pain relief was more than 60%. A follow up was carried out over the following 6 months. The treatment was effective in 71% of patients in group A, and 36.4% of group B (p < 0.007). The pain disappeared completely in 44.7% of group A and 15.2% of group B (p < 0.01). During the six month follow-up period, in those patients in whom the response to the treatment was effective, the pain recurred in 34.8% of group A and in 70% of group B. No cutaneous, ophthalmologic or systemic side effects were observed. These results suggest that irradiation with GaAs laser at the doses used and techniques applied in this study, relieves chronic low back pain in older patients in a statistically significant percentage of the patients but without causing any adverse side effects.

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