The orbital septum forms the fibroid, connective-tissue flaps of the eyelids, as well as the frontal boundary of the eye socket. When the eyes move around in their sockets, it is this tissue that keeps the eyelids steady. The orbital septum is penetrated by nerves and veins that service both lids, as well as the lacrimal gland that regulates tear production. Fat pads that line the lower eyelid are part of the septum, and lid retractor tendons are attached to these areas to open and shut the lids. A rupture or weakening of the septum often occurs with age, causing lids to droop.
There are muscles that stretch over the orbital septum, and the lateral palpebral ligament is cushioned from it by a fat pocket where it attaches to the eye socket. The septum also stretches in behind the Horner muscle, which holds the lacrimal tears sac. What are called tarsal plates form the dense fibroid structures of the eyelids. Other ligaments and tendons help to stabilize the lids and attach to the socket through the septum. The lids receive nourishment from internal and external carotid arteries, and the conjunctiva's translucent membrane lines the insides of the lids with cushioning mucous.
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The eyes receive some protection from the structures of the eyelid portions of the orbital septum. The eyelids work to produce continuous tear lubrication over the cornea of the eye to maintain a protective film layer during blinking. Additionally, the orbital septum is moved upon by the orbicularis oculi muscle to enable voluntary winking and when forced closure of the eyelids is needed to protect the eye's surfaces. The fibrous material of the eyelids is formed in a mesh of horizontal and vertical fiber lines to further stabilize the lids through their attachment deep in the orbital septum.
Lid retractor smooth muscles and levator muscles regulate eyelid tension and allow movement of the lids up and down for the upper lid. The lower lid retractors are made up of the inferior rectus muscle and fascial extensor muscle fibers that together with oblique muscles allow lower lid movements upward and are interspersed with extra fat pockets with age. Additional fat pads in the upper eyelids are found behind the orbital septum and surrounding the lacrimal gland.
Besides the weakening septum of drooping eyelids with age, other disorders connected with the orbital septum can arise over time. Fatty infiltrations of some of the muscles and ligaments of this tissue can result in a condition called orbital cellulitis. This fatty infection is potentially life-threatening and can cause severe distortions of the tissues of the eye and forehead regions. It can also spread staph, streptococcus, or septic infections throughout the body via the central nervous system. Additionally, conjunctivitis and thyroid eye diseases can cause considerable swellings in orbital septum areas.