AGING AND MICRORELIEF OF SKIN 149 l'.

150 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS age (years) E •- •o =o 2'0 .'o 6'ø e•o ' age (years) Figure 4. Leg: evolution ooe the first axis ooe oeurrow versus age. a. Line density ___ S.oe. b. Mean d½lxh --- S.E. sarily deepen. Our measurements verify this. Important differences were observed be- tween the limbs and the face, especially as related to density and deepness of furrows. In the peri-orbital area, density plateaued at age 30-40. This could suggest that, statisti- cally, "crows feet" are set by 35 years of age. Depth, however, increased eightfold, reaching 200 microns in the sixties. On the leg the changes, as expected, were less impressive. The depth increased by only 65 to 80% and, as a consequence, the CDSS only increased slightly. The lateral leg is a site which is minimally subjected to physical forces of stretching deformations. Since it is relatively protected against UV radiation, the major surface changes probably reflect biologic or intrinsic aging. In youth, the skin relief shows a network of shallow furrows. The reservoir of deformation, as expressed by the CDSS, is low (1.02), since there is a limited demand for stretching and accommodation to muscle movements. Leg furrows were not greatly influenced by age. The first axis kept its orientation perpendicular to the direction of constraints, reflecting the dynamics of extension. The second one shifted progressively toward the limb axis. This is a classic response to joint movement. The leg perhaps resembles the forearm, which we studied previously (5), in that it is relatively protected and reflects mainly endogenous aging changes. We anticipated that aging would influence these two regions differently. It is