Characteristics of Upper Eyelid Thickness in Asians.

Purpose: This study examines the characteristics of upper eyelid thickness in Asians microscopically.

Materials and methods: Histological evaluations of 20 upper eyelids (10 right and 10 left) from 14 Japanese cadavers (age range, 36-97, years; average, 68.9 years) were performed. Specimens were fixed in 10% formalin, stained with Masson trichrome and Elastica van Gieson, and analyzed for anterior protrusion of preaponeurotic fat and skin and subcutaneous tissue thickness at 10 mm from the eyelid margin. Statistical analyses included 1-way ANOVA and the Tukey multiple comparison test, with significance set at p < 0.05.

Results: Upper eyelid thickness was classified into 3 types: very thick, moderately thick, and thin types. The very thick type (7 eyelids in 6 cadavers) showed significant anterior protrusion of preaponeurotic fat beyond the superior tarsal edge, pushing the orbicularis oculi muscle anteriorly, with thick subcutaneous tissue. The moderately thick type (5 eyelids in 4 cadavers) exhibited preaponeurotic fat fully reaching the septum-aponeurosis junction with minimal anterior muscle displacement, with less thick subcutaneous tissue. The thin type (8 eyelids in 6 cadavers) demonstrated preaponeurotic fat failing to reach the septum-aponeurosis junction, with thinner subcutaneous tissue. Subcutaneous tissue was significantly thicker in very thick types compared with moderately thick types (p = 0.002) and thin types (p = 0.000). It was similar in the moderately thick type and the thin type (p = 0.356). Skin thickness did not differ significantly between groups (p = 0.078).

Conclusions: Upper eyelid thickness in Asians is primarily influenced by the anterior protrusion of preaponeurotic fat and subcutaneous tissue thickness, with significant variations across the 3 identified types.