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Medical Definition of Orbital rim
1. The mostly sharp edge of the orbital opening which is the peripheral border of the base of the pyramid-shaped orbit. The superior half of the orbital rim is the supraorbital margin; the inferior half is the infraorbital margin. The frontal, maxillary, and zygomatic bones contribute to the orbital rim, which is generally strong to protect the orbital contents. Weak, potential fracture sites of the rim coincide with the sutures between the participating bones. Synonym: margin of orbit. (05 Mar 2000)