ABSTRACT
The orbital septum is a thin, firm, multilayered fibrous tissue that originates from the arcus marginalis, the thickened periosteum of the superior and inferior orbital rim. In the Occidental upper eyelid, the septum extends toward the tarsal plate where it fuses with the levator aponeurosis 2 to 5 mm above the superior tarsal border ( 2 ). The site of fusion and/or the position of the orbital fat varies between Occidental and Asian eyelids. In the Occidental lower eyelid, the orbital septum fuses with the capsulopalpebral fascia at, or slightly below, the inferior tarsal border. The fused complex inserts on the anterior and posterior tarsal surfaces at the inferior border of the tarsus. Laterally, the septum is contiguous with the lateral horn of the levator aponeurosis and the lateral canthal tendon. The septum functions as an anatomic barrier between intraorbital and extraorbital structures, specifically the orbital fat. As a result of aging, the septum may become attenuated contributing to anterior herniation of the orbital fat in the upper and lower eyelids. Surgically, the septum should be distinguished from the levator aponeurosis in the upper eyelid. The septum should not be sutured to avoid eyelid retraction, restriction of eyelid movement, or incarceration in the surgical wound ( 2 ).
