LOW-LEVEL LASER THERAPY (LLLT) AND SAFETY CONSIDERATIONS

Although the low-power HeNe lasers and diode lasers used for low-level laser therapy (LLLT) and photoactivation of biological processes are usually thought to be ''safe'', the possibility that such lasers can cause biological effects raises the question of whether such laser action may, under some conditions, be adverse and thus be unsafe. Some research data can be interpreted as evidence for adverse effects. Laser safety standards classify all CW HeNe lasers with an output power below 1 mW as ''Class 2,'' as they are not considered a realistic hazard, whereas most HeNe lasers with an output power between 1 and 15 mW are Class 3A or 3B. Most diode lasers used for LLLT are considered Class 3B. Safety control measures for ocular hazards are expected for Class 3A and 3B laser exposures, but any adverse effects of LLLT will result from long-duration, high-level doses to parts other than the eyes. The hazards will be systemic rather than ocular, and, thus, need evaluation. The safety implications of current knowledge regarding LLLT are discussed with regard to the demonstrated effects in cell cultures, and on vitamin D synthesis in regard to calcium metabolism in adults.