Anisotropy of light propagation in human skin

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 propagat ion at the same position. This anisotropy is believed to be caused by the p referential orientation of collagen fibres in the dermis, as described by L anger's skin tension lines. Monte Carlo simulations that examine the effect of partial collagen fibre orientation support this hypothesis. The observa tion has consequences for non-invasive diagnostic methods relying on skin o ptical properties, and it could be used non-invasively to determine the dir ection of lines of cleavage in order to minimize scars due to surgical inci sions.