Journal of Clinical and Aesthetic Dermatology

APR 2018

An evidence-based, peer-reviewed journal for practicing clinicians in the field of dermatology

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32 JCAD JOURNAL OF CLINICAL AND AESTHETIC DERMATOLOGY April 2018 • Volume 11 • Number 4 O R I G I N A L R E S E A R C H duration used in the study (100ms) is similar to a biologically occurring time period. The time period in question might be, for example, the half-life of a mitochondrial membrane ion channel or that of another membrane in the cell that responds to light. The nitric oxide photodissociation theory might also provide a partial explanation, specifically in terms of the requirement for different pulsing patterns during LED therapy. An understanding of the light-producing mechanism of fireflies provides insight. Fireflies similarly pulse their light. A flash of light is produced when oxygen reacts with the luciferyl intermediate. The flash switches itself off though. Light dissociates nitric oxide from cytochrome c oxidase. Oxygen is then allowed to bind again. Subsequently, the mitochondria consume oxygen, enabling the luciferyl intermediate to build up until more nitric oxide arrives. 41 In this study, we used a specific sequential pulsing code with a 50-percent duty cycle based on previous in-vitro studies performed in our laboratory. 8,35,37 The best combination of parameters to downregulate hyperpigmentation was pulse duration (PD) set at 500µs, pulse interval (PI) at 150µs, number of pulses per pulse train (PT) set at three, and pulse train interval (PTI) at 1,550µs (Figure 5). Longer PTIs, or dark zones, might play a key role in optimizing tissue response for melasma. Some possible explanations are that several peak power pulses (at 90mw/cm 2 ) are needed first, followed by a longer pause (PTI) not only to reduce possible tissue hyperthermia that could increase melanocytic activity but also for probable inhibition of pigment-related cell signaling pathways. Clinical trial. This split-face pilot study with a successful response (Figure 6) to pulsed PBM brings an alternative treatment modality to melasma, which is a complex, almost untreatable, acquired pigmentary disorder. In this study, the PBM-treated side versus the control side showed statistically significant results for pigment reduction using three measurement methods (4-point scale observation by three physicians, MASI score, and melanin index score). To our knowledge, it is the first study reporting the use of PBM for melasma. Limitations. There are two study limitations: the small number of patients involved and the short length of follow-up. Long-term results are FIGURE 4. Mechanical microdermabrasion decreases photon scattering and increases epidermal turnover and blood flow (vasodilation), leading to the induction of an immediate mild inflammatory infiltrate—The mobilization phase is immediately followed by the modulation phase, since photobiomodulation works best on dynamic inflammatory processes modulating specific cell signaling pathways. FIGURE 5. Pulsing pattern definitions—pulse duration (PD): LED on; pulse interval (PI): LED off; pulse train (PT): number of pulses/train; pulse train interval (PTI): LED off (longer interval or dark zone); in this example, PT=3 FIGURE 6. Patient 7 at baseline and at Week 12

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