Orbital Tumors - Bone Anatomy

Orbital Anatomy

The orbits are conical or four-sided pyramidal cavities, which open into the midline of the face and point back into the head. Each consists of a base, an apex and four walls. They protect the eye from mechanical injury

The base, which opens in the face, has four borders. The following bones take part in their formation:

  1. Superior margin: frontal bone
  2. Inferior margin: maxilla and zygomatic
  3. Medial margin: frontal, lacrimal and maxilla
  4. Lateral margin: zygomatic and frontal


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


WALL BONES CONTENTS Clinical Correlation  

Lesser wing of sphenoid

lacrimal gland fossa
trochlea 4mm posterior to margin for superior oblique tendon

Supraorbital notch/foramen

subperisteal abscess

Medial Wall


Ethmoid - thinnest


lacrimal sac fossa
cribiform plate is medial to anterior orbit at the level of fronto-ethmoidal suture

Nasoclacrimal duct obstructions./tumors/DCRs
Medial wall fractures

subperisteal abscess

Orbital cellulitis/proptosis from ethmodial extension


Maxillary- second thinnest, thins posteriorly


infraorbital foramen
inferior oblique origin

slopes 20 degrees down

suspensory ligament of eyeball

subperiosteal abscess
blow-out fractures

Lateral Wall

Zygomatic bone
Greater wing of sphenoid

lateral orbital tubercle is 11mm below F-Z suture
serves as attachment of check ligament of lateral rectus

Tripod fractures
Ruptured globes

Lateral tarsal strips

adjacent to middle cranial fossa, temporal fossa, and pterygopalatine fossa








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