The arcus marginalis is the name for a localized rim of thickening where the eyelid's orbital septum attaches to the orbital bone (junction of E and K shown below).
||Epidermis on surface, dermis below
||Eyelid closing muscle
||Tarsus (Tarsal Plate)
||Stiffening element (like cartilage)
||Layer holding back the orbital fat
||Fat from the socket extending into lid
||Inferior Oblique Muscle
||Muscle moving the eyeball
||Lower Eyelid Retractors
||Structures that move the lid downward
||Bone surrounding the eye; socket
||Lining of the back of eyelid and front of eye
||Lining of the bone (called 'periorbita' in orbit)
The term arcus marginalis release is sometimes used by blepharoplasty surgeons to describe a cosmetic operation on the lower eyelid in which fat surrounding the eyeball is moved out of the orbit and over the rim of orbital bone to try to fill in an upper cheek depression, or tear trough. To accomplish this, the arcus marginalis must be disinserted from its bony attachment.
The operation is better described by the term "lower eyelid fat repositioning," even though the fat moved is actually from the orbit rather than the eyelid.