148 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1.50 I .40. 1.30 I .20 1 1.00- 0 20 40 60 80 age (years) Figure 2. "Crow's foot" wrinkles: evolution of the CDSS with age. LEG The main axis of the primary lines was oriented at 125 ø in childhood, turning back to 73 ø in both adults and the aged (Figure 3). The secondary axis, present in fifty percent of children and adults, was first at 95 ø, then shifted to 151 ø. Only thirty percent of the aged maintained a secondary axis close to the leg axis (165ø). The number of primary lines (Figure 4a) increased up to age 35, plateauing at this age. Similarly, the depth of furrows increased up to age 35, plateauing from age 35 to 65. The depth of furrows then increased with further aging (Figure 4b). Consequently, the CDSS increased mod- estly in a similar fashion (Figure 5). DISCUSSION One difficulty in interpreting age-associated changes in the skin relief concerns the relative contribution of each factor involved in the process: mechanical stress, actinic damage, and biological aging. We approach the problem by selecting two very different skin sites for study. Linear wrinkles as "crows j%t" originate in aging skin as a result of contraction of the peri-orbital muscles which terminate in the skin itself. Especially in lax, actinically damaged skin, muscle action throws the skin into deep folds which eventually become permanent etchings. With the passage of time and loss of elasticity, "crows feet" neces-

AGING AND MICRORELIEF OF SKIN 149 l'.