Discussion

Narrowband incoherent IR-A LED photobiomodulation within the action spectra of 580 nm to 860 nm should rejuvenate exposed skin by positively modulating overall cellular levels, increasing dermal collagen synthesis, and down-regulating matrix metalloproteinases. The final clinical result of LED photobiomodulation should therefore correlate with progressive dermal structural changes triggered by sequential exposures to specific wavelengths. Two major potential drawbacks of this interesting approach to skin rejuvenation are identified by the short temporal coherence (coherence length) and the low spatial or lateral coherence characterising narrowband LED, making treatment distance between light source and irradiated surface crucial for the effectiveness of photobiological events. The more monochromatic the light, the longer the length where the light field is coherent in volume, and the smaller the divergence of the light beam at the point of irradiation ²³. These particular physical aspects of LED radiation allow for uniform irradiance on highly irregular skin surfaces, like the human face. Most LED delivery systems consist of linear stripes of variable length, regularly distributed along flat or curved panels. This feature showed to be only partially effective in ‘recontouring’ the complex anatomy of the human face.

In the present study a novel narrowband sequentially combined 840 nm CW + 880 nm PW LED facial mask light delivery system has proven to be safe and effective in reducing facial wrinkle count, improving overall skin texture, tone, and elasticity. A minor increase in surface spotty dyspigmentation count was detected by computerised facial feature analysis by Visia Complexion Analysis, 15 and 45 days after the treatment. This particular finding could be explained as a sub-clinical post-inflammatory hyperpigmentation (PIH) due to a micro-thermal paracrine-cytokine signaling up-regulation of keratinocyte and fibroblast alpha-Melanocyte Stimulating Hormone (MSH) release P53-dependent ^24–25. The majority of study subjects considered the treatment quite effective (90–100%) and acceptable, both intra-operatively, and post-operatively. The combination of CW emission immediately followed by PW emission may possibly explain the high degree of clinical success in improving premature facial skin ageing.

The initial part of LED irradiation, consisting of CW light emission, could have been associated with a photobiochemical and moderately photothermal ‘priming’ of exposed cells, preparing the ground for a better response to the on–off biostimulatory effect induced by PW irradiation during the final part of the treatment. The idea of evenly distributing LED arrays along the inner surface of an anatomically designed polystyrene facial mask has shown to be quite effective in keeping light delivery distance as short and constant as possible (8 mm ± 4 mm), all along the complex surface anatomy of facial skin. This particular innovative feature could have been responsible for a consistent optimisation of facial irradiance and consequently, for the overall photobiological effectiveness of this treatment.

Small sample size and full-face treatment represent two study limitations, but split-face studies are already planned to further prove the efficacy of this interesting non-invasive skin rejuvenation protcol.

Conclusion

Predominantly non-thermal high-energy LED photobiomodulation performed with an innovative facial mask light delivery system using a sequential combination of 840 nm CW and 880 nm PW irradiation has proven effective in positively modifying skin tone and texture of prematurely aged facial skin. Clinical results were confirmed by objective and subjective assessment 15 and 45 days after completion of full treatment sessions. Textural, wrinkle, and skin elasticity modifications were found more pronounced 15 days after the end of the eight LED treatments and showed a slight decrease after 45 days, thus indicating the need for a periodical repetition to keep tissue functional improvements. Sequential combined narrow-band CW + PW LED treatment was reported to be painless, safe, and easy to perform.

The combination of such visible and consistent aesthetic improvement and the feasibility of the treatment sessions led all study subjects, in the end, to agree in recommending an anti-ageing treatment with EPI-C Plus 840–880 nm LED facial mask. The innovative LED array distribution on the inner aspect of an anatomically designed facial mask positively contributed to the consistency of clinical results owing to the almost constant minimal distance between light sources and facial skin surfaces. More studies are needed to identify maintenance treatment intervals to keep clinical results within an acceptable range, aiming at an effective, long-lasting ‘healty ageing’ protocol.