REDUCING FACIAL WRINKLE SIZE USING POLYMERS 135 SKIN IMAGING METHODS Facial images of the subjects were obtained with a VISIA-CR 2D facial imaging system (Canfi eld Scientifi c, Fairfi eld, NJ) and with an AEVA-HE 3D Imaging System (Eotech SA, Marcoussis, France). The VISIA records and automatically analyzes left, right, and frontal facial views, but does not capture depth information on facial features such as pores and wrinkles. VISIA-CR 2D images were taken as full face images with front, left, and right views. The AEVA-HE 3D system uses fringe projection and cameras to analyze the topography of the skin surface, including wrinkles and other surface features. The skin roughness is calculated as two parameters, the arithmetic mean of the surface roughness, Sa, and the root mean square of the surface roughness, Sq. Additional parameters used by the AEVA system are the curvature area and density, defi ned as the area of all features that have a cer- tain set curvature and the ratio of that area to the total area, respectively. We used a curvature set point of 0.5–1.0 mm, which corresponds to fi ne lines in the skin. The higher values of curvature area or density suggest more visibility of the fi ne lines. Finally, AEVA also reports total detected wrinkle area and volume, which are determined by the instrument software. AEVA images were recorded as full face images with 160 mm focal length lenses. The zones for analysis were the cheek and crow’s feet areas. CONSUMER PERCEPTION Subjects’ perception of product performance and acceptance was evaluated through self- administered questionnaires, using an internet-based survey administrator (SurveyMonkey). The subjects completed the questionnaires individually without any extrinsic infl uences such as other volunteers or the results of technical measurements. The consumer percep- tion questionnaires instructed subjects to consider the entire half face to which they had applied product when completing the questionnaire. STATISTICAL ANALYSIS For the clinical instrument data, we computed the descriptive statistics (means, standard deviation, and standard errors of the mean (SEM) of each parameter and the change of each parameter before and after product application. The percentage change from baseline was calculated by subtracting each subject’s baseline parameter value from the value after product application. Statistical analysis of the change in the parameters was conducted with Minitab® software (Minitab, Inc., State College, PA). The normality of the data distribution was confi rmed with the Kolmogorov–Smirnov test and the equality of variances was confi rmed with a Levene’s test. Once normality and equal variance were confi rmed, a paired t-test was conducted to compare the parameters before and after product application. In addition, a one-way analysis of variance (ANOVA) followed by Tukey’s test was conducted to compare the before and after application change of each parameter for the four different treatment products at 95% confi dence level (p-value 0.05). The consumer perception data were analyzed with Minitab® software as well. Perfor- mance parameters were evaluated through the use of a 6-point scale (1 = not at all 2 = slightly 3 = somewhat 4 = moderately 5 = very and 6 = extremely). A 5-point scale

JOURNAL OF COSMETIC SCIENCE 136 (1 = slightly 2 = somewhat 3 = moderately 4 = very and 5 = extremely) was employed to evaluate the perception of reduction in wrinkle visibility. To determine differences in the perception ratings among the test products, a one-way ANOVA at a 95% confi dence level ( p-value 0.05) was performed for each parameter followed by a Tukey comparisons test. Again, the normal distribution and equality of variances were confi rmed for each parameter through a Kolmogorov–Smirnov test and a Levene’s test, respectively, before the ANOVA. RESULTS POLYMER GLASS TRANSITION MEASUREMENTS The polymers investigated differ markedly in their response to environmental humidity (Figure 1). The PVP absorbs over 50% water at 90% relative humidity, leading to a decline in glass transition temperature to below freezing. The dependence of Tg on polymer con- tent confi rms the pattern measured by Buera et al. (14). On the other hand, the AMC absorbs much less water even at 90% relative humidity and its decline in Tg is much less steep. Signifi cantly, the Tg is near room temperature at high water levels. This indicates that at room temperature the glass transition of AMC solutions is reached after evapora- tion of a relatively small amount of water compared with PVP. MECHANICAL PROPERTIES OF THE SKIN Treatment of the facial skin with the polymer formulations made skin fi rmer in both Cutom- eter and Ballistometer measurements. All polymers increased fi rmness signifi cantly over baseline as measured by Cutometer parameters R0 and R3 (Figure 2). Moreover, the 4% AMC formulation increased skin fi rmness signifi cantly more than the placebo. There was no signifi cant difference in skin tightening between the 4% AMC, 2% AMC, and PVP formulations, nor was there a signifi cant difference between the 2% AMC, PVP, and placebo formulations. Fig ure 1. Glass transition temperature and water absorption of solid polymer material exposed to different levels of relative humidity.