Skin optics

The current status of tissue optics is reviewed, distinguishing among the cases of dominant absorption, dominant scattering, and scattering about equal to absorption. Previously published data as well as some current unpublished data on (human) stratum corneum, epidermis, and dermis are collected and/or (re)analyzed in terms of absorption coefficient, scattering coefficient, and anisotropy scattering factor. It is found that the individual skin layers show strongly forward scattering (anisotropy factors between 0.7 and 0.9). The absorption and scattering data show that for all wavelengths considered, scattering is much more important than absorption. Solutions to the transport equation for a multilayer skin model and finite beam laser irradiation that take this into account are not yet available. Hence, any quantitative dosimetry for skin treated with (laser) light is inaccurate.