Anatomy of a "black eye": a newly described fascial system of the lower eyelid.

The anatomy of a black eye is examined in a series of cadaver dissections in which a previously unreported fascial system of the lower eyelid is identified. This fascia originates at the orbital rim, and is in continuity with the orbital septum and with the periosteum of the orbital floor and anterior maxillary wall. This fascia contributes to the thickened area along the orbital rim called the arcus marginale. At the level of the orbicularis oculi muscle, this fascia was noted microscopically to fuse with a fibrous septa of the superficial cheek fat. This creates one long continuous membrane from the orbital rim above to the cheek skin below. Dye injection techniques show that this membrane is impermeable and traps injected dye in the same place where a black eye forms. After periorbital injury, extravasated hemoglobin pigment is confined to the area above the cutaneous insertion of this membrane. This fascial system has been named the septum malaris: malar describes its origin along the orbital rim of the cheek, and septum further describes the partitioning nature of this ultra-thin membrane.