LC-OCT: A Revolutionary Tool for Cosmetic Efficacy and Skin Safety Assessment
The field of cosmetic efficacy evaluation in China is developing rapidly, and the trend of cosmetic efficacy claim evaluation has gradually shifted from focusing mainly on macroscopic skin surface features in the early stages to microscopic skin tissue structure. The traditional method of studying skin tissue structure requires skin biopsies, which have strict ethical requirements and high testing costs.
With advancements in large-scale optical device technology, non-invasive detection methods have gained widespread application in in vivo microscopic skin tissue structure research due to advantages like high subject compliance and suitability for long-term monitoring of changes at identical sites. Among them, Line-field Confocal Optical Coherence Tomography (LC-OCT), combines the advantages of Reflectance Confocal Microscopy (RCM) and Optical Coherence Tomography (OCT), can simultaneously achieve horizontal and vertical skin tissue scanning, effectively improving visualization depth and image acquisition speed, and has attracted much attention in cosmetic efficacy evaluation.
Introduction to LC-OCT Imaging Technology
LC-OCT operates by measuring laser light reflection from cells, achieving in vivo cellular-level resolution of human skin in both horizontal (C-scan) and vertical (B-scan) modes, obtaining non-invasive vertical and horizontal tissue slices and 3D images. With an acquisition rate of 10 images per second, measuring a single test site takes only 30–60 seconds.
At present, this technology has been miniaturized and can be installed in ergonomic handheld probes to evaluate product efficacy in real-time in vivo, providing strong support for the diagnosis of skin lesions.
Application of LC-OCT in Cosmetic Efficacy Evaluation
Whitening and Spot-Reduction Efficacy Evaluation
Traditional whitening and spot removal evaluation methods (e.g. skin colorimetry, melanin testing, subjective assessment) mainly focus on surface color changes and cannot provide information on the morphology, distribution, and quantification of melanin.
LC-OCT non-invasively observes subcutaneous tissue structural changes at the cellular level. Use LC-OCT to image tiny color spots caused by photoaging and create a Dermal-Epidermal Junction (DEJ) fluctuation map of the color spots. By calculating the DEJ fluctuation and melanin volume density, studies show that after using whitening and spot removing products, the melanin in the epidermis of the subjects significantly decreased, but there was no significant change in DEJ fluctuation, indicating that LC-OCT can independently characterize the depth of pigmentation and provide a new method for evaluating the whitening and spot removing efficacy of cosmetics.
Anti-Wrinkle and Firming Efficacy Evaluation
Wrinkles and sagging is mainly due to changes in the structure of the dermis layer. The currently used imaging devices (high-frequency ultrasound, OCT, RCM, etc.) have limitations in evaluating skin structure due to limitations in device resolution and scanning penetration depth.
LC-OCT has cellular resolution and visualizes the network structure of the dermis by real-time acquisition of superficial images of the dermis. Thus, analyzing dermal fiber network density via LC-OCT imaging can serve as an effective method for evaluating anti-wrinkle and firming cosmetics efficacy.
Application of LC-OCT in Skin Safety Assessment
Follicle Visualization
LC-OCT achieves greater vertical visualization depth, enabling visualization of hair follicles. In hair removal treatment, LC-OCT can observe perifollicular inflammation and spongiotic hyperplasia, confirming diode lasers' targeted follicular effects while protecting surrounding epidermis. Therefore, LC-OCT can be effectively used for hair removal treatment or safety evaluation of hair removal products, and indicates the potential of LC-OCT to optimize treatment processes in other medical beauty processes involving lasers.
Sensitive Skin Grading
Traditional patch testing has problems such as high experience requirements for evaluators, false positives, and false negatives in the diagnosis and grading of contact allergic dermatitis. LC-OCT has the advantage of observing subcutaneous cellular structures and allows detailed microanatomical characterization of acute allergic contact reactions. Results show high-resolution LC-OCT imaging can detect subclinical changes in suspected patch test lesions and differentiate healthy skin, allergy, and irritation at the cellular level.
