Is light-emitting diode phototherapy (LED-LLLT) really effective?

Abstract

Background: Low level light therapy (LLLT) has attracted attention in many clinical fields with a new generation of light-emitting diodes (LEDs) which can irradiate large targets. To pain control, the first main application of LLLT, have been added LED-LLLT in the accelerated healing of wounds, both traumatic and iatrogenic, inflammatory acne and the patient-driven application of skin rejuvenation. Rationale and Applications: The rationale behind LED-LLLT is underpinned by the reported efficacy of LED-LLLT at a cellular and subcellular level, particularly for the 633 nm and 830 nm wavelengths, and evidence for this is presented. Improved blood flow and neovascularization are associated with 830 nm. A large variety of cytokines, chemokines and macromolecules can be induced by LED phototherapy. Among the clinical applications, non-healing wounds can be healed through restoring the collagenesis/collagenase imbalance in such examples, and 'normal' wounds heal faster and better. Pain, including postoperative pain, postoperative edema and many types of inflammation can be significantly reduced. Experimental and clinical evidence: Some personal examples of evidence are offered by the first author, including controlled animal models demonstrating the systemic effect of 830 nm LED-LLLT on wound healing and on induced inflammation. Human patients are presented to illustrate the efficacy of LED phototherapy on treatment-resistant inflammatory disorders.

Conclusions: Provided an LED phototherapy system has the correct wavelength for the target cells, delivers an appropriate power density and an adequate energy density, then it will be at least partly, if not significantly, effective. The use of LED-LLLT as an adjunct to conventional surgical or nonsurgical indications is an even more exciting prospect. LED-LLLT is here to stay.

Keywords: Grotthus-Draper law; acne rosacea; dissecting cellulitis; irritant contact dermatitis; nonhealing wound; photochemical cascade; photophysical reaction.

Fig. 1:

Range of typical bioreactions associated with a surgical laser and their approximate temperature range. Note that some degree of photoactivation almost always occurs simultaneously with HLLT-mediated reactions. (Data adapted from Calderhead RG: Light/tissue interaction in photosurgery and phototherapy. In Calderhead RG. Photobiological Basics of Photosurgery and Phototherapy, 2011, Hanmi Medical Publishers, Seoul. pp 47–89)

Fig. 2:

The process of cellular photoactivation by low level light therapy (LLLT). Visible light induces a primary photochemical response particularly associated with mitochondrial cytochrome c-oxidase, whereas near IR induces a primary photophysical response in the cellular and organelle membranes. However the eventual photoresponse is the same. (Based on data from Karu & Smith, Refs 6 & 9)

Fig. 3:

Patient satisfaction curves compared for LED-mediated skin rejuvenation with 633 nm alone, 633 nm + 830 nm combined and 830 nm on its own, showing the numbers of patients who rated their improvement as excellent on a 5-scale rating. The first set of columns represents the findings immediately after the 8^th of 8 weekly sessions, twice per week for 4 weeks. The 2^nd, 3^rd and 4^th sets of columns are the findings at post-treatment weeks 4, 6 and 8 respectively. At all stages, LED phototherapy with 830 nm produced superior satisfaction. The increase over the post-treatment period is interesting, suggesting improved results through continued tissue remodeling as part of the LED-mediate wound healing process. (Data adapted from Ref 24)

Fig. 4:

Mechanisms underlying the three main LLLT endpoints, particularly associated with the wavelength of 830 nm, although 633 nm has beneficial effects as well.

Fig. 5:

HeaLite II LED phototherapy system, Lutronic Corp, Goyang, South Korea.

Fig. 6:

The wound healing value compared between the group treated with 830 nm LED (Tx group) with LED and the unirradiated Con group without LED. Note that the 1 LED-irradiated animal in the 0–25% group had somehow removed the wound dressing very early in the experiment. (Adapted from Ref 28)

Fig. 7:

The changes in dermatitis-associated inflammatory cells following 830 nm LED irradiation in the rat model (A: Control specimen, B: LED irradiated specimen). A marked reduction in inflammatory infiltration is evident.

Fig. 8:

Improvement in a patient (24-year-old female) with treatment-resistant post-chemical peel irritant contact dermatitis (AHA-related ICD) seen above at baseline, and below 10 days later following 3 830 nm LED treatment sessions, 3 days apart, 20 minutes per session (60 J/cm²)

Fig. 9:

Dramatic improvement in a case of dissecting cellulitis of the scalp (34-year-old male) (a) at baseline and (b) following 830 nm LED treatment (twice per week for 2 weeks, 20 min per session to give 60 J/cm²)

Fig. 10:

Improvement of acne rosacea (33-year-old female) at baseline (a) and following LED treatments (once per every week for 6 weeks, 20 min and 60 J/cm² per session) (b). Although not very well noted in the grayscale illustrations, the small acneiform papules have disappeared, with a clear decrease seen in the redness on both cheeks.