The orbital septum is a weak membranous sheet, attached to the orbital rim where it becomes continuous with the periosteum
It extends into each eyelid and blends with the tarsal plates and, in the upper eyelid, with the superficial lamella of levator palpebrae superioris.
The orbital septum is thickest laterally, where it lies in front of the
lateral palpebral ligament.
It passes behind the medial palpebral ligament and nasolacrimal sac, but in front of the pulley of superior oblique.
The septum is pierced above by levator palpebrae superioris and below by a fibrous extension from the sheaths of inferior rectus
and inferior oblique.
The lacrimal, supratrochlear, infratrochlear and supraorbital nerves and vessels pass through the septum from the orbit en route to the face and scalp. Clinically, the septum is an important
anatomical reference to differentiate pre- and postseptal (orbital) cellulitis.