The orbital septum, a thin, multilayered sheet of fibrous tissue, arises from the periosteum over the superior and inferior orbital rims at the arcus marginalis. In the upper eyelid, the orbital septum typically fuses with the levator aponeurosis 2–5 mm above the superior tarsal border, and below the superior tarsus in eyelids of Asian individuals (see Figs 9-10, 9-11). In the lower eyelid, the orbital septum fuses with the capsulopalpebral fascia at or just below the inferior tarsal border. Along with a small contribution from the inferior tarsal smooth muscle, the fused capsulopalpebral–orbital septum complex inserts on the posterior and anterior tarsal surfaces as well as the inferior border of the tarsus. Over time, thinning and attenuation of the septum and laxity of the orbicularis muscle contribute to anterior herniation of the orbital fat pads.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.