Adipose body of the orbit.

The adipose body of the orbit (ABO) fills most of the orbital cavity, surrounding the eyeball, muscles, nerves, and vessels. It was studied in histologic section in the three basic planes in the fetus, neonate, and adult. In the retrobulbar area, that is, posterior to the eyeball, adipose tissue occupies the space around the optic nerve and penetrates between the recti muscles, describing a four-leafed clover pattern in frontal section. The fatty tissue of the retrobulbar area also includes the peripheral ring of fat that lies between the muscles and the walls of the orbit. In the part of the peribulbar area located between the muscular insertions on the eyeball anteriorly and the emergence of the optic nerve from the sclera posteriorly, the pattern of adipose tissue is identical to the peripheral ring of fat and the fat between the muscles in the retrobulbar area. External to the muscular insertions and the anterior part of the eyeball, there is a thin ring of histologically similar fatty tissue that is continuous anteriorly with the fatty bodies of the upper and lower eyelids. Histologic examination shows that the lobules are large in that part of the retrobulbar area within the muscle cone and that they are smaller with more fibrous septa in the remaining restricted regions, such as the area between the eyeball and muscles and in the rings around the muscles and around the eyeball. In no case was a septum found separating the peripheral adipose ring from the fat located within the muscle cone. Copyright 2002 Wiley-Liss, Inc.