The Use of P45 Plastination Technique to Study the Distribution of Preseptal and Preaponeurotic Fat Tissues in Asian Eyelids.

This study evaluated the anatomical features of preseptal and preaponeurotic fat tissues in the upper eyelids of individuals of Asian heritage. Specifically, we attempted to elucidate the role of these tissues in the formation of sunken upper eyelids and devise an easy and feasible approach to rectify this. Sixteen heads (32 facial halves) from fresh adult cadavers were processed using the P45 plastination techniques. The polymer resulted in transparent plastination, and the sagittal median section of the eyeballs was dissected. Gross anatomy results of 12 adult cadaveric heads (24 facial halves) were included as supplementary data. The orbital septum was observed on sagittal section slides prepared with P45 sheet plastination. Based on the amount of fat distribution, the upper eyelid was classified into three groups: preseptal fat predominant type, preaponeurotic fat predominant type, and orbital septum equilibrium type (relative distribution of 31.3, 12.5, and 56.3 % in plastinated slices, and 29.2, 16.7, and 54.2 % in gross anatomical studies). Major tissues on P45 sheet plastination slices in the supraorbital region were preseptal fat, preaponeurotic fat, frontalis muscle and frontalis muscle aponeurosis, and partial orbicularis oculi muscle. The muscle fibers of the frontalis muscle and orbicularis oculi were interconnected and extended backward to connect with the orbital septum through preseptal fat. In conclusion, the morphology and external appearance of the upper eyelids depend on the relative relationship between preseptal and preaponeurotic fat tissues. Mildly or moderately sunken upper eyelids can be corrected by modifying the soft tissue in the supraorbital margin.