In vivo multiphoton imaging of the eyelid skin

Multiphoton tomography (MPT) has become an important imaging method for non-invasive and high-resolution imaging of the skin in vivo. Due to the nonlinear excitation, by using near-infrared (NIR) light, 3D information is intrinsically provided. In combination with fluorescence lifetime imaging (FLIM), it is possible to obtain both structural and metabolic data. Human in vivo measurements are usually limited to easily accessible regions. However, often imaging of specific body parts such as the eyelid are of interest for cosmetic reasons. By using the clinically certified multiphoton imaging tomograph MPTflex this demand can be fulfilled. An articulated mirror arm and scan-detector head enable imaging at otherwise difficult-to-access areas. We show the characterization of the epidermal and upper dermal layers of the eyelid skin of human volunteers in vivo based on endogenous autofluorescence intensity, lifetime, and second-harmonic generation signals. Skin properties such as the epidermal thickness were also assessed. Furthermore, the influence of an anti-aging cream on the eyelid and forearm skin was investigated. Changes of the skin epidermis autofluorescence lifetime were observed after two-weeks long application of an anti-aging cream. The SHG-to-AF aging index of dermis (SAAID) increased during that time.