Differences in the surface and subsurface reflection characteristics of facial skin by age group.

Background/purpose: The age-dependent changes of facial skin imperfections such as spot or wrinkles have been investigated repeatedly by means of various objective measurements. However, the age-dependent changes in the optical-reflection characteristics that create a perception of a shine or a glow of the skin have received little attention. We evaluated the age dependence of the optical-reflection characteristics of the surface and subsurface facial skin layers of three age groups.

Methodology: The facial skin of 83 Japanese females ranging in age from 20 to 49 years was examined using a high-resolution digital camera equipped with a linear polarizing filter under polarized illumination. Surface and subsurface reflection components were extracted by means of an image-processing technique. In addition to the reflection characteristics, skin hydration, the melanin index, and the hemoglobin index were also measured.

Results: Significant age-dependent changes were found in the evenness of the surface reflection and in the intensity of the subsurface reflection. In contrast, no difference was observed in the intensity of the surface reflection or in the evenness of the subsurface reflection. The melanin index showed a significant age-dependent difference, with a trend similar to that of the subsurface reflection intensity, but the skin hydration and hemoglobin index showed no difference by age group.

Conclusion: Surface and subsurface reflection characteristics show age-dependent changes. Younger skin has a greater subsurface reflectivity and a more even surface reflectivity. These optical characteristics of the skin might be related to the perception of consumers that younger skin is brighter and more radiant with an internal glow, whereas aged skin is shinier or glossier.