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Orbital Bones

Orbital Anatomy

• Orbital volume and dimensions: = 30 cc, 35(Height) x 45(Width) x 45 mm(medial wall depth), globe 25 x 25 mm
• Bones: (F)rontal, (M)axillary,(Z)ygomatic, (L)acrimal, (E)thmoid, (P)alatine, (S)phenoid

Orbital Walls and Openings

Superior orbital fissure (SOF):

• 22 mm long
• separates greater wing of sphenoid from lesser wing of sphenoid
• transmits third, fourth, sixth and V1 AND SYMPATHETIC FIBERS
• lateral rectus origin separates into superior and inferior divisions
  • Superior division transmits lacrimal, frontal and trochlear nerves
  • Inferior division transmits superior and inferior divisions of CN III, nasociliary branch of CN V, CN IV, superior ophthalmic vein, and sympathetic nerve plexus
  • Venous system: superior ophthalmic vein

Inferior orbital fissure (IOF)

• Located between lateral orbital wall and the orbital floor
• Transmits V₂ ( maxillary) , pterygoid nerves  nerve arising from pterygopalatine ganglion
• infraorbital nerve (a branch of V₂) enters the infraobital groove and infraorbital canal for sensation to lower eyelid, cheek, upper lid, upper teeth
• Venous system inferior ophthalmic vein

Holes/Notches/Canals

Nasolacrimal canal Nasolacrimal canal

• lacrimal sac fossa to the inferior meatus
• separates greater wing of sphenoid from lesser wing of sphenoid
• transmits third, fourth, sixth and V1 AND SYMPATHETIC FIBERS
• lateral rectus origin separates into superior and inferior divisions
  • Superior division transmits lacrimal, frontal and trochlear nerves
  • Inferior division transmits superior and inferior divisions of CN III, nasociliary branch of CN V, CN IV, superior ophthalmic vein, and sympathetic nerve plexus
  • Venous system: superior ophthalmic vein

Supraorbital foramen/notch

• transmits blood vessels
• supraorbital nerve
• Anterior/posterior ethmoidal foramen: transmits ethmoidal blood vessels and nerve
• Zygomatic foramen: transmits zygomaticofrontal and zygomaticotemporal nerves, zygomatic artery
• Nasolacrimal duct (NLD): exits into inferior meatus
• Infraorbital canal: transmits infraorbital nerve (V₂)

Ethmoidal foramina

• anterior ethmoidal artery
• posterior ethmoidal artery
• allows infections and neoplasms to enter to orbit from the sinuses

Optic Canal

• 8-10 mm long
• located within the less wing of sphenoid
• separated from SOF by OPTIC STRUT
• Transmits. Ophthalmic nerve, ophthalmic artery, sympathetic nerves
• Optic foramen is 6.5 mm wide: it may possibly be enlarged in the presence of optic nerve glioma; 1 mm of asymmetry between right and left is abnormal