The formation, structure, and firmness of the desired eyelid fold are determined by biological components beneath the surface, especially in the areas surrounding the eyes where fat is stored. The size of these fatty tissues can fluctuate based on water retention levels, which are influenced by puberty, sleep quality, diet, stress, rubbing the eyelids, and decrease with age.
Regardless of gender, age, and ethnic background, adult human eyeballs exhibit no statistically significant differences in dimensions. On the other hand, the dimensions of adult human skulls, which significantly impact facial shape, do display statistically significant variations linked to gender, age, and ethnic background. The manner in which the skin envelops the periorbital area, shaped by the spherical eyeball, determines the alignment of skin tension lines, which can either enable the formation of a double eyelid crease or strengthen an existing crease.
The supratarsal crease is a wrinkle in the upper eyelid skin that conforms to a specific skin tension line. When water retention levels fluctuate, the crease may alter its configuration to align with a different skin tension line. Due to the unique nature of each eye, even minor differences can determine how one eye is affected by changes in skin water retention.