Anatomical and Histological Study of the Upper Tarsus in Asian

The aim of this study was to observe and analyze the anatomical and histological characteristics of the upper tarsus in Asian.

A total of 15 Asians (14 adults, 1 child) were used. The sagittal sections with thickness of 3 μm in the middle of the upper eyelid were prepared and stained with hematoxylin-eosin, Masson trichrome and anti-smooth muscle actin antibody staining, and then were observed and photographed under light microscopy.

On the sagittal section, the upper end of the tarsus was connected with the Müller muscle and the part of the posterior layer of the levator aponeurosis; the lower end was the inflated part of the palpebral margin; the superficial surface was connected with the pretarsal fascia; and the deep surface was connected with Müller muscle aponeurosis and palpebral conjunctiva. Histologically, the tarsus was similar to the structure between dense fibrous connective tissue and cartilage, and its main structures include meibomian glands and its ducts, accessory lacrimal glands, glands of Moll, glands of Zeis, eyelash hair follicles, Riolan muscle, blood vessels, and collagen fibers. Through the observation of the tarsus of a child, compared with the adult specimen, the meibomian gland tissue was more abundant; the collagen fibers density was significantly lower and arranged orderly; the blood vessel density was significantly higher; α-SMA positive smooth muscle cells could be seen in the upper end of the tarsus and its superficial and deep surfaces.

In this study, the internal and adjacent anatomical structures of the upper tarsus in Asians were observed under a microscope, and according to the histological characteristics, the tarsus was divided into 3 parts and 3 types. Through the preliminary analysis, the tarsus was likely to show different histological characteristics in different individuals and age groups of Asians. There was a certain correlation between the degree of meibomian gland atrophy, the degree of collagen fibrosis and the density of blood vessel in the tarsus.