Objective To identify a relationship between dermal thinning and wrinkle formation.
Design We assessed the wrinkle depth of the forehead and lateral canthus of 58 male and female human cadavers (range of age at death, 29-93 years) using image analysis and measured the dermal thicknesses in Azan-Mallory –stained skin sections obtained around the wrinkles.
Setting Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan.
Main Outcome Measures The maximum depth of the wrinkle was obtained from the forehead and lateral canthus. The dermal thickness was measured at the deepest point of the wrinkle (wrinkle point) and at a location where no wrinkle existed within 1 mm of its surface (nonwrinkle point). The ratio of the dermal thickness at the wrinkle point to the dermal thickness at the nonwrinkle point was calculated.
Results The dermal thickness underneath a wrinkle decreased as the depth of the wrinkle increased (P < .001). When the dermis became thinner than one-half of its original thickness, the dermis stopped thinning. Microscopic observations revealed that the junction between the dermis and subcutaneous layers under advanced wrinkles curved downward with invaginations of the dermis into the subcutaneous layer.
Conclusions The dermis under a wrinkle becomes thinner in association with the progression of wrinkles until the dermis becomes thinner than one-half of its original thickness. When the dermis stops thinning, wrinkles develop further by dermal invagination into the subcutaneous layer.