Anatomical histological and mesoscopic study of the adipose tissue of the orbit

Our study aimed to define the organization of the orbital adipose tissue, which is constituted from white adipose tissue. Six orbital samples were taken by dissection from fresh cadavers. After fixation and paraffin-embedding, the blocks were sectioned in the three spatial planes (two in the frontal, two in the sagittal, two in the horizontal). Semi-serial sections of 7 microm were then stained with hematein, eosin, safran or Masson trichrome green. We noticed strong areas of adhesion with orbital bones located at the lacrimal gland, the orbital trochlea and the inferior orbital fissure. Our mesoscopic and histological results allowed the description of two types of orbital adipose tissue corresponding to morpho-functional topographic variations. One was constituted of thick conjunctival septa with small adipocytes near muscles and the lacrimal gland. This was a supporting tissue that gave the points of rotation. The other was constituted of thin conjunctival septa with larger adipocytes near the optic nerve, allowing its movements in the orbit. These morphological differences appeared to be correlated with the mechanical role of these two areas. The dense appearance could correspond to the functional trochlea of rectus muscles described. In contrast we did not observe the systematic radial and concentric conjunctival meshwork classically described. This study underlines the specificity of orbital adipose tissue, which could be useful for a better understanding of its normal and pathological partition and its involvement in ocular motility.