Analyzing the in vivo cutaneous effects of diode laser treatment using line‐field confocal optical coherence tomography

Line-field confocal optical coherence tomography (LC-OCT) is a burgeoning optical imaging device that allows real-time, high resolution, in vivo assessment of skin.1 LC-OCT uses a laser to gauge the reflection of light from cellular structures.2 LC-OCT has the capability to generate three-dimensional image by visualizing up to 500 μm using quasihistological vertical (optical coherence tomography) and horizontal (reflectance confocal microscopy) views.2 LC-OCT allows greater depth of visualization, and faster image acquisition allowing real-time monitoring, quantitative analysis, and visualization of hair follicles that can allow optimization of aesthetic procedure such as laser hair removal. According to 2020–2021 Aesthetic Plastic Surgery National Databank Statistics, hair removal is one of the most widely performed nonsurgical procedure in the United States.3 Diode lasers are regarded as a revolutionary technology in the field of depilatory treatment, providing an efficient and long-term solution by targeting the hair follicles. They offer a great patient experience by minimizing discomfort and pain, as well as reducing the risk of adverse effects through the incorporation of cooling systems.4 Additionally, diode lasers provide quick treatment sessions due to their ability to treat a large area along with high repetition rates.4 As previously known, diode lasers for hair removal involve selective photothermolysis, which selectively targets the melanin pigment in the hair follicles while minimizing absorption by the epidermis leading to perifollicular erythema and edema as the optimal endpoint.4 The goal of our study was to visualize and evaluate these changes through the lens of LC-OCT and highlight the possible utility of this nascent imaging device. Laser hair removal using diode laser was performed on three subjects with Fitzpatrick skin type II. Preset mode for their skin types was used on diode laser. LC-OCT was used to capture images before and after laser treatment session. Images were captured in vertical, horizontal, and 3D modes. Hair follicles were seen located in the dermal layer and presented with different brightness and shapes. When analyzing pre- and post-treatment images, perifollicular inflammation was appreciated in vertical, horizontal, and 3D views post-treatment, presenting as hyper-reflective cells, mild spongiosis, and perifollicular edema (Figures 1, 2). Inflammation and spongiosis are more prominent around the hair follicle, confirming that diode laser specifically targets hair follicles and spared surrounding epidermis. Based on these findings, LC-OCT confirms that preset laser settings work well in hair removal. Most laser devices come with preset modes for each skin type that are effective, and many practitioners prefer to use these preset settings. In our study, LC-OCT confirms the effectiveness of preset modes. In rare instances where a preset mode is not effective, settings can be modified to change the wavelength and fluence, followed by clinical and LC-OCT correlation. This may allow treatment optimization and personalization that will result in maximum efficacy, reducing adverse effects such as skin irritation, pigmentation, and burns. LC-OCT may allow for treatment optimization not just for laser hair removal but for other cosmetic procedures involving lasers. The data that support the findings of this study are available from the corresponding author upon reasonable request.