New classification for single-system light treatment

Abstract

Background and Aims: Although the use of the laser in medical applications has increased dramatically during the last three decades, it is significant that during the last few years non-laser light sources have gained prominence in photomedicine and photosurgery, particularly the use of lightemitting diodes (LEDs) and intense pulsed light (IPL). The author therefore believed it was important to devise a new classification of light/tissue interactions, and that the well-accepted acronym LLLT and HLLT should now stand for low level light therapy and for high level light treatment, since the 'L' in 'laser', LED and IPL stands for 'light'. Rationale: The author herein presents a classification, which is based on the level of reaction induced by the light incident on tissue, rather than being based on the system used to deliver the light energy. When the level of tissue reactivity to light of very low incident power and energy densities is well below the cells' damage threshold, so that instead of being damaged the cells are directly activated by the low incident photon density, the changes in the irradiated tissue are pho- toactivative and reversible: the author hereafter refers to this group of reactions as low level light therapy (LLLT). When the level of tissue reactivity to light of very high incident power and energy densities is over the cells' damage threshold, so that the cells are directly destroyed, the changes in the irradiated tissue are photodestructive and irreversible: the author hereafter refers to this group of reactions as high level light treatment (HLLT). For levels of tissue reaction intermediate to HLLT and LLLT, the author suggests the new term, medium level light treatment (MLLT), as described in detail herein. Conclusions: When the new classification system of light treatment (LT) is understood and used, the author feels this offers an accurate and simple method of classifying light/tissue reactions by the therapeutic reaction itself, rather than by the light source, laser, LED, IPL system or other, used to produce the reaction. © 2011 JMLL, Tokyo, Japan.