Anisotropy of light propagation in human skin

TLDR

Anisotropy in skin light propagation is attributed to collagen fibre orientation along Langer's skin tension lines. The study aims to explore how this anisotropy can inform non‑invasive diagnostics and guide incision placement to reduce scarring. Spatially resolved diffuse reflectometry revealed a directional dependence in visible and near‑infrared light propagation through human skin, with the reduced scattering coefficient varying by up to a factor of two, a result supported by Monte Carlo simulations.

Abstract

Using spatially resolved, steady state diffuse reflectometry, a directional dependence was found in the propagation of visible and near infrared light through human skin in vivo. The skin's reduced scattering coefficient mu(s)' varies by up to a factor of two between different directions of propagation at the same position. This anisotropy is believed to be caused by the preferential orientation of collagen fibres in the dermis, as described by Langer's skin tension lines. Monte Carlo simulations that examine the effect of partial collagen fibre orientation support this hypothesis. The observation has consequences for non-invasive diagnostic methods relying on skin optical properties, and it could be used non-invasively to determine the direction of lines of cleavage in order to minimize scars due to surgical incisions.