Morphological Study of the Relationship Between Solar Elastosis and the Development of Wrinkles on the Forehead and Lateral Canthus

Figure 1. Image analysis variables used to quantify the degree of solar elastosis. The ratio of solar elastosis dermal thickness to full dermal thickness (elastosis ratio) was assessed at wrinkle points and at nonwrinkle points. a Indicates full dermal thickness at a wrinkle point; b, solar elastosis dermal thickness at the wrinkle point; c, full dermal thickness at a nonwrinkle point; d, solar elastosis dermal thickness at the nonwrinkle point; D, dermis; E, epidermis; SC, subcutaneous tissue; and SE, solar elastosis.

Figure 2. Representative images of forehead wrinkles (from the left, external appearance, 3-dimensional replica images, and tissue specimens [insets are enlarged on the far right]). A, Shallow wrinkle in an 80-year-old man (maximum depth, 0.17 mm; elastosis ratios of 0.16 at wrinkle point and 0.17 at nonwrinkle point). B, Mid-depth wrinkle in an 80-year-old woman (maximum depth, 0.22 mm; elastosis ratios of 0.05 at wrinkle point and 0.34 at nonwrinkle point). C, Deep wrinkle in a 72-year-old woman (maximum depth, 0.59 mm; elastosis ratios of 0.26 at wrinkle point and 0.51 at nonwrinkle point). Microscopic observations of the external appearance were made along the blue line. Three-dimensional replica images were obtained and analyzed at the same area as the external appearance. Color bar indicates the level of the surface. D indicates dermis; E, epidermis; FM, facial muscle; I, inferior direction; S, superior direction; SC, subcutaneous tissue; SE, solar elastosis; and *, wrinkle point. Elastica–van Gieson stain, original magnification ×40. The external appearance and 3-dimensional replica images in C are reproduced from our previous article.⁹

Figure 3. Representative images of lateral canthus wrinkles (from the left, external appearance, 3-dimensional replica images, and tissue specimens [insets are enlarged on the far right]). A, Shallow wrinkle in a 54-year-old woman (maximum depth, 0.12 mm; elastosis ratios of 0.02 at wrinkle point and 0.06 at nonwrinkle point). B, Mid-depth wrinkle in a 66-year-old man (maximum depth, 0.54 mm; elastosis ratios of 0.58 at wrinkle point and 0.80 at nonwrinkle point). C, Deep wrinkle in a 72-year-old woman (maximum depth, 1.4 mm; elastosis ratios of 0.68 at wrinkle point and 0.83 at nonwrinkle point). Microscopic observations of the external appearance were made along the blue line. Three-dimensional replica images were obtained and analyzed at the same area as the external appearance. Color bar indicates the level of the surface. D indicates dermis; E, epidermis; FM, facial muscle; I, inferior direction; S, superior direction; SC, subcutaneous tissue; SE, solar elastosis; and *, wrinkle point. Elastica–van Gieson stain, original magnification ×40. The external appearance and 3-dimensional replica images in C are reproduced from our previous article.⁹

Figure 4. Relationships between elastosis ratios and wrinkle depths at wrinkle points. A, In forehead regions (y = 0.0001 x + 0.083, R² = 0.02). B, In lateral canthus regions (for shallow wrinkles <0.6 mm, y = 0.0006 x^1.06, R² = 0.22; for deep wrinkles ≥0.6 mm, y = 2.27 x^−0.25, R² = 0.007). NS indicates not significant.

Figure 5. Relationships between elastosis ratios and wrinkle depths at nonwrinkle points. A, In forehead regions (y = 0.0006 x + 0.14, R² = 0.17). B, In lateral canthus regions (for shallow wrinkles <0.6 mm, y = 0.0052 x^0.76, R² = 0.21; for deep wrinkles ≥0.6 mm, y = 3.46 x^−0.25, R² = 0.05). NS indicates not significant.