Efficacy of minimally invasive nonthermal laser-induced optical breakdown technology for skin rejuvenation

Abstract

We demonstrate the efficacy of a novel minimally invasive nonthermal skin rejuvenation technique for wrinkle and fine-line reduction based on laser-induced optical breakdown. The optical breakdown caused by tightly focused near-infrared laser pulses creates a grid of intradermal lesions without affecting the epidermis, leading to skin rejuvenation. The pilot in vivo efficacy test performed on five subjects successfully demonstrates wrinkle and fine-line reduction, and improvement of other skin features without pain or any other unpleasant sensations or any social downtime associated with the treatment. The efficacy is evaluated objectively and subjectively by assessing the improvement of wrinkles and/or fine lines or skin texture after the treatment. The treatment is safe without side effects or social downtime, and all test subjects reported that the treatment is "perceptible but not painful." Four out of the five subjects who participated in this pilot study were assessed to have "minor" to "significant" improvements of wrinkles and fine lines by the professional panels. The results of this clinical study are expected to bring a paradigm shift in the present laser- and light-based skin rejuvenation methods by introducing a safe treatment procedure without damaging the epidermis, with no or little social downtime and with an efficacy that might be comparable to ablative techniques.

Fig. 1

Schematic representation of lesion creation in dermis using laser-induced optical breakdown (a). Skin specimen taken 30 min after treatment, stained with Herovici staining. Control skin specimen stained with Herovici staining (b). Circled are microlesions visualized by the staining technique (c). Skin specimen taken at 30 days after treatment was stained with Herovici staining. The mature collagen (collagen I) stained in red whereas the young collagen (collagen III) stained in blue

Fig. 2

Photos of subject 1 before the treatment and 1 week, 1 month, and 3 months posttreatment

Fig. 3

Fitzpatrick wrinkle grade (0, no lines; 1–3, fine lines; 4–6, fine to moderate-depth wrinkles, moderate number of lines; 7–9, moderate to deep wrinkles, numerous lines with or without redundant skin folds) for subjects 1, 2, 3, and 5, assessed by three dermatologists (D1, D2, and D3) before, 1 week, 1 month, and 3 months after treatment

Fig. 4

Mean improvements of skin features for subjects 1, 2, 3, and 5 assessed by the dermatologist team at different timelines after the completion of treatment: 1 week (red bar), 1 month (green bar), and 3 months (blue bar). Individual score of improvement from each dermatologist is differentiated by three symbols: dermatologist 1 (circles), dermatologist 2 (diamonds), and dermatologist 3 (stars), respectively

Fig. 5

The mean improvements of skin features assessed by the independent expert panel