A quantitative assessment of the human skin surface using polarized light digital photography and its dermatologic significance

Background: Quantitative and objective investigations of parallel-polarized light (PPL) photography for dermatologic purposes are scarce. Objective:: To determine the significance of quantitative analysis of PPL photography to develop objective measurement methods of skin surface characteristics. Method:: For PPL photography, a digital camera, a light-emitting diode illuminator, and polarizing filters were arranged and kept constant. We analyzed the PPL photography images of the glabella, the medial aspect of the forearm, and the posterior aspect of the lower leg, and measured the CIELAB values. A dermatologist evaluated the clinical severity of the actual photographed sites with respect to glossiness and dryness. These clinical severities were compared statistically with the CIELAB values. Results: According to the correlation analysis, the L^* value was negatively correlated with dryness (r=-0.29869, P=0.0047) and glossiness (r=-0.35367, P=0.0185). Conclusion: The method used in this study is applicable to the quantitative evaluations of other dermatologic diseases or conditions, especially in relation to skin surface changes.