Thickness of the Medial Pretarsal Adipose Tissue in the Upper Eyelid among the Japanese Population.

PURPOSE:To investigate the medial pretarsal adipose tissue thickness of the upper eyelid in the Japanese population. METHODS:Sixty-two whole upper eyelids were harvested from 35 Japanese cadavers and fixed in paraffin. The samples were cut into 5 µm sagittal microsections and stained with hematoxylin and eosin, as well as Masson's trichrome. Data obtained from images and measurements were taken with Aperio ScanScope and ImageScope software and underwent statistical analysis. RESULTS:The samples were divided into 3 shapes sagittal cross-sections of the eyelid (triangular, rectangular, and flat) corresponding to the shape of the medial pretarsal adipose tissue. Type I (triangular shape, 48.4%) had a ratio of fat thickness at 1⁄2 tarsal height to peak fat thickness of <0.9, and type IIa (rectangular shape, 30.6%) and IIb (flat shape, 21.0%) had pretarsal adipose tissue thickness to tarsal height ratio of ≥0.2 and <0.2, respectively. The mean values of tarsal thickness at 1⁄2 tarsal height were 1021 µm for the type I group, 1100 µm for the type IIa group, and 764.4 µm for the type IIb group (p = 0.01). The mean values of fat thickness at 1⁄2 tarsal height were 410.6 µm for the type I group, 303.3 µm for the type IIa group, and 242.6 µm for the type IIb group (p = 0.26). CONCLUSIONS:The thickness of the medial pretarsal adipose tissue was different according to the shape of the sagittal cross-section of the eyelid. Awareness of the medial pretarsal adipose tissue thickness contributes to effective suture placement and safe suture depth during blepharoptosis surgery.