In vivo Three-Dimensional Birefringence Analysis Shows Collagen Differences between Young and Old Photo-Aged Human Skin

Polarization-sensitive optical coherence tomography (PS-OCT) permits non-invasive visualization of dermal birefringence, mainly due to collagenous structures. The purpose of this study is to use PS-OCT to assess intrinsic-age-related and photo-age-related differences in three-dimensional dermal birefringence. We measured dermal birefringence of the cheek skin and photo-protected interior upper arm skin from old and young volunteers. The algorithm that we used automatically produces the transversal dermal birefringence map from the polarization-sensitive OCT volume. This allowed quantitative comparison and visualization of the transverse distribution of the dermal birefringence. We found that dermal birefringence of the cheek skin was significantly smaller in the old group than in the young group (young group, 0.295±0.037° μm−1; old group, 0.207±0.03° μm−1; P=0.003), whereas the interior upper arm showed no age-dependent difference. The transversal map of the cheek showed a heterogeneous decrease in dermal birefringence due to photoaging. The maps suggested that the peripheral regions of some infundibula were surrounded by a strong collagen network. Three-dimensional analyses of dermal birefringence using PS-OCT help to quantify the diagnosis of photoaging.