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

• Floor

  • Bones
    • Maxillary- second thinnest, thins posteriorly
    • Zygoma
    • Palatine

  • Contents
    • infraorbital foramen
    • inferior oblique origin
    • slopes 20 degrees down
    • suspensory ligament of eyeball

  • Clinical Correlations
    • subperiosteal abscess
    • blow-out fractures

• Lateral wall
• Bones
  • Zygomatic bone
  • Greater wing of sphenoid

• Contents
  • lateral orbital tubercle is 11mm below F-Z suture,
    • serves as attachment of check ligament of lateral rectus
• Clinical Correlations
  • Tripod fractures
  • Ruptured globes
  • Lateral tarsal strips
  • adjacent to middle cranial fossa, temporal fossa, and pterygopalatine fossa

• The medial orbital walls are nearly parallel and are 25 mm apart
• The orbit is widest not at its entrance, but 1 cm from the orbital rim

Fissures

• 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

• 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 be enlarged in the presence of optic nerve glioma; 1 mm of asymmetry between right and left is abnormal