Imaging of lashes

Imaging is a minimally invasive technique to quantify various parameters of human lashes. Observational studies with different age categories demonstrated that lashes change with age.^{22, 23} Characteristics such as the orientation, length, thickness and pigmentation were measured from photographs of the lower and upper lids.^{22, 23} Human and mouse eyelash life cycle phases have been estimated with photographs in several studies.^{7, 9, 13, 33} However, the measures were variable from one study to another due to non-standardized methodologies. To improve accuracy, Thibault et al. observed preselected lashes over a nine-month period by measuring their length each week.⁹ Once again, while imaging of lashes estimates the parameters of the life cycle, more advanced techniques described above, such as xenotransplantation and follicle cultures, are routinely used to measure the same parameters for hair.²⁹

Imaging techniques have also been utilized for ethnic differences between the lashes of Caucasian and Asian women.⁷ Digital photographs were used to calculate the lift-up and curl-up angles of the upper lashes and phototrichogram (allows in vivo study of the growth cycle)³⁴ for the number, length and thickness of lashes.⁷ Smaller lash details such as the cuticle textures and layer density were observed ex vivo with electron microscopy.⁷