ANATOMY OF ORBIT
BONY ORBIT
SKULL
Cranial bones 8
facial bones 14
22 bones
BONY
ORBIT
1. Frontal
2. Zygomatic
3. Maxilla
4. Lacrimal
5. Ethmoid
6. Sphenoid
7. Palatine
Some bones of the skull are called pneumatic bones
They have inside air cavities, named sinuses
• Frontal bone
• Sphenoid bone
• Ethmoid bone
• Maxilla
Fetal- round orbit
Adult- quadrangular
Bony orbit
Quadrilateral Pyramid
APEX
BASE
ROOF
FLOOR
MEDIAL WALL
LATERAL WALL
Base of the orbit
F
ON THE FACE
 Quadrangular
 Formed by
Z
M
 Frontal
 Maxilla
 Zygomatic
 Orbital margins
 Sharp
 Fetus, infants, children,
female
 Rounded
 male
APEX
Extends into the
cranial cavity
WALLS
Medial - Oblong
LateralTriangular
Roof Floor-
• SUPERIOR
– Frontal bone
ORBITAL MARGIN
• INFERIOR
FRONTAL
– Zygomatic
– Maxilla
• MEDIAL
– Maxilla
– Frontal
• LATERAL
– Zygomatic
– Frontal
ZYGO
MAIC
MAXILLA
Superior margin
• Antero medially
– Trochlea
• 4 mm behind the orbital
margin
• Supra trochlear notch
– Supra trochlear nerve & vessels
• Arnold’s notch
– 6mm medial
– Supra orbital nerve & vessels
• Supra orbital foramen
– Supra orbital nerve & vessels
– Supra ciliary canal (Ward) allows nerve
and vessels to frontal air sinus
ROOF
• Orbital part of frontal bone
• Lesser wing of sphenoid bone
• Thin wall
 Absorption in old age
 Periorbita in contact with
meninges
 Penetrating wound injury to
frontal lobe of brain
 Frontal sinus may invade the
roof
ROOF
• Under the roof
– Frontal nerve
– Blood vessels
– Levator palpebrae superioris
• Antero laterally
– fossa lacrimal gland
• Accessory fossa of RochanDuvigneaud (occasional)
– Behind the fossa for lac gland
– Lodges orbital pad of fat in
fetus and children
FLOOR
• Length 47.6mm
– Straight in infants
– Oblique in adult
• Bones
– Maxilla
– Zygomatic
– Palatine
• Inferior orbital
fissure/canal
• Attachment of inferior
oblique muscle
FLOOR
• Related to
– Maxillary air sinus
• 0.5-1mm thick
• Tumor invades causing
proptosis
– Inferior rectus muscle
– Inferior oblique muscle
• Inferior orbital fissure
– Infra orbital nerve
– Zygomatic nerve
– Veins connecting
infratemporal region
MEDIAL WALL
• Parallel to each other
• Bones
– Frontal process of maxilla
– Lacrimal
– orbital part of Ethmoid
– body of Sphenoid bone
• Thin wall
– Translucent
– 0.2-0.4mm thick
– Lamina paprycea
• Ethmoidal foramen
• Lacrimal groove
– Lacrimal sac
• Ethmoidal air sinus
MEDIAL WALL
• Related to
 ethmoidal air sinuses
 Spread of infection- orbital cellulitis
 Nasal cavity
 Tumors from nasal cavity can
breach lamina papraycea
 Optic canal (posteriorly)
 Lacrimal fossa (inferomedially)
 Superior oblique
 Medial rectus
 Ethmoidal nerve and vessels
 Infratrochlear nerve
 Terminal branches of ophthalmic
artery
LATERAL WALL
• Oblique 45° angulation
• Bones
– Orbital surface of zygomatic bone
– Orbital surface of greater wing of
sphenoid
– Thickness variable from anterior to
posterior
• Whitnall’s tubercles
– 11 mm below the frontozygomatic
suture and 4-5mm behind the
lateral margin
– Attachments to
• Lateral check ligament
• Suspensory ligament
• Aponeurosis of LPS
• Lateral palpebral ligament
• Lacrimal gland fascia
LATERAL WALL
• Separates
– Temporal fossa
– Middle cranial fossa
• Related to
– Lateral rectus muscle
– Lacrimal gland
– Lacrimal nerve
– Lacrimal vessels
• Lateral approach for orbitotomy
• During resection of maxilla,
Whitnall’s tubercle is spared
– Damage to Suspensory ligament
– Displacement of eyeball
ORBITAL PERIOSTEUM
• PERIORBITA
• Endosteum of Dura
• Continues as orbital septa at the
margins of the orbit
• Thickens to forms the common
tendinous ring of Zinn
• Orbitalis muscle (Muller’s) around
inferior orbital fissure
• Firmly attached on the medial wall
• Lacrimal fascia around the gland and
sac
• Pulley around oblique superior muscle
ORBITAL PERIOSTEUM
• Periorbita
 Liable to ossification around inferior orbital fissure,
posterior lacrimal crest
 Richly innervated (pain sensation)
 Lacrimal, zygomatic, infra orbital, ethmoidal nerves
 Due to loose attachment shifted by pus, blood ,
surgical procedures
SUPERIOR ORBITAL FISSURE
• 22 mm long
• Lies between roof and
lateral wall
• Orbital cavity to
middle cranial fossa
• Common tendiness
ring divides into three
compartment
INFERIOR ORBITAL FISSURE
• Connects
– Infratemporal fossa
– Pterygopalatine fossa
• Muller’s muscle
• Infraorbital nerve V2
• Zygomatic nerve
– Pterygopalatine ganglion
• Branch of inferior ophthalmic vein
connecting pterygoid plexus of
veins
Optic canal
• Lies in lesser wing of sphenoid
• Foramen in infants
• Canal in adult
– 10-11 mm length
– Funnel shaped
– Circular in middle part
– Vertically Oval at orbital end
– Horizontally oval at cranial end
• Related to
– Sphenoidal air sinus
– Post. ethmoidal air sinus
– Sinusitis may result in optic neuritis
• Optic nerve with meninges (subarachnoid
space)
• Ophthalmic artery
FORAMINA
• Lateral wall
– Zygomatico temporal
– Zygomatico facial
• Medial wall
– Anterior /posterior
ethmoidal foramen
• Inferomedial angle
– Lacrimal fossa
– Lacrimal sac
CONTENTS
• PERIOBRBITI
– MODIFICATIONS
• ORBITAL PAD OF FAT
• TENON’S CAPSULE/FASCIA BULBI/
• ORBITALIS MUSCLES
• NERVES
– II, III, IV, VI, BRANCHES OF V1,
– CILIARY GANGLION, BRANCHES OF V2
• OPHTHALMIC ARTERY
• OPHTHALMIC VEINS
• EYEBALL
ORBITAL FASCIA
• Interwoven connective tissue
• Covers intra orbital structures
• Modifications
– Fascia bulbi/Tenons capsule
– Fascial sheath of extra ocular
muscles
– Fascial expansions
FASCIAL SHEATH OF
THE EYEBALL
• Bulbar sheath/Tenon’s capsule
• Encloses major part of eyeball
• Separated from eye ball by episcleral
space
• Near sclerocorneal junction to around
the point of entry of optic nerve
• Fascia is pierced by
– Ocular muscles
– Optic nerve
– Ciliary nerves and vessels
– Venae vorticosae
Fascia sheath expansions
• Lateral check ligament
• Medial check ligament
• Suspensory ligament of
Lockwood
• Muscle pulleys from orbital wall
– Well developed around MR
• Expansion from SR to LPS
– Synergetic action during
elevation and opening of eye
lid
Fascia sheath expansions
• From SO to Lacrimal gland
as superior transverse
ligament of Whitnall
– Check the movement of LPS
• Suspensory ligament of
fornix
– Between SR, LPS and fornix
– Surgical cut may cause
prolapse of conjunctiva
• Orbital septa from
periorbita to fascia bulbi
ORBITAL INDEX
ℎ𝑒𝑖𝑔ℎ𝑡
•
𝑥100
𝑤𝑖𝑑𝑡ℎ
• Megaseme
– ≥ 89 𝑀𝑜𝑛𝑔𝑜𝑙𝑖𝑎𝑛
• Mesoseme
– > 89-83 Caucasian
• Microseme
– ≤ 83 Negroid
AGE CHANGES
• At birth
 Ossified margin for protection during
parturition
 Orbital cavity large
• Child
 Orbital cavity looks laterally
 Superior and inferior orbital fissures
are wider (later becomes narrow due
to the growth of greater wing of
sphenoid)
 Distance between the orbit are small
(adult the distance is increased with
growth of frontal and ethmoidal air
sinuses
• Old age
 Bony absorption ( common in roof,
lateral wall and less in medial wall)
Surgical spaces in orbit
• Sub periosteal space
– Bone and periorbita
• tumors/hemorrhage/ pus may
elevate
• Peripheral orbital space
– Periorbital fascia covering the
muscles
– Contains peripheral orbital fat
– Tumours/haemongioma
• Central (Retrobulbar space)
– Deep to recti muscles and behind
the eye ball
– Contains optic nerve, ciliary nerves
, vessels, III,IV,VI, ciliary ganglion,
central fat
• Episcleral space
CLINICAL ANATOMY
• Limited space between wall and
eye ball
– Space occupying lesions may cause
proptosis
• Trauma to the orbit
– Superior margin
• Damage/displace trochlea pulley
• Symptoms of SO muscle involvement
– Lateral margin
• Depression of cheek
– Floor/medial wall
• Blow-out fracture
– Roof
• Penetrating wounds from sharp
objects
– Frontal lobe of brain