Orbit

 EMBRYOLOGY
 ANATOMY
 APPLIED
ASPECTS
- OPTOM FASLU MUHAMMED

INTRODUCTION
 Orbit is the anatomical space bounded:
 Superiorly – Anterior cranial fossa
 Medially - Nasal cavity & Ethmoidal air sinuses
 Inferiorly - Maxillary sinus
 Laterally - Middle cranial fossa & Temporal fossa

EMBRYOLOGY
 Orbital walls- derived from cranial neural crest
cells which expand to form:
 Frontonasal process
 Maxillary process
 Lateral nasal process + Maxillary process =
medial, inferior and lateral orbital walls
 Capsule of forebrain forms orbital roof

 Early in the human
development eyes point
almost in the opposite
direction.
 As the facial growth occurs,
the angle between the optic
stalks decreases and is ~68˚
in an adult.
EMBRYOLOG
Y

OSSIFICATION
Enchondral
Membranous
EMBRYOLOG

 Frontal, Zygomatic, Maxillary and Palatine bones-
Intramembranous origin
 First bone- Maxillary (at 6 wks of intrauterine life)
- develops from elements in the region of the canine tooth
- secondary ossification centres in the orbitonasal and
premaxillary regions
 Other bones develop at around 7 wks of intrauterine
life
EMBRYOLOG

 Sphenoid bone- both enchondral and
intramembranous origins
Lesser wing of the sphenoid- 7 wks (Enchondral)
Greater wing of the sphenoid- 10 wks
(Intramembranous)
Both wings join- 16 wks
 Ossification is complete at birth (except orbital apex)
EMBRYOLOG

CLINICAL SIGNIFICANCE
DERMOID CYSTS:
 Most common orbital
cystic lesions
 Origin:
◦ Pouches of ectoderm
trapped into bony
sutures
◦ Most common site
frontozygomatic suture

CEPHALOCOELES:
 Reflect orbital
entrapment of
neuroectoderm
 Most commonly-
◦ At the junction of frontal
& ethmoid
 Pathology:
◦ Herniation of brain
parenchyma into the
orbit
EMBRYOLOG

FIBROUS DYSPLASIA:
 Benign, developmental
fibro-osseous lesion
 Origin:
◦ Arrest in maturation at
woven bone stage
 Pathology:
◦ Bone replaced by
fibrous tissue
EMBRYOLOG

DIMENSIONS
 Quadrilateral pyramid
 Base - forwards, laterally, downwards
 Apex - optic foramen
 Volume of orbital cavity ≈ 30 cc in adults

 Rim:
- Horizontally ≈ 40 mm
- Vertically ≈ 35 mm
 Interorbital width
 ≈ 25 mm
 Extraorbital width
 ≈ 100 mm
 Depth
◦ Medially ≈ 42 mm
◦ Laterally ≈ 50 mm
DIMENSIONS

COMPOSED OF:
 7 Bones:
 Ethmoid
 Frontal
 Lacrimal
 Maxillary
 Palatine
 Sphenoid
 Zygomatic
Right orbit
FSlMLESbMZPZSz 2432

4 WALLS
ROOF FLOOR
MEDIAL
WALL
LATERAL
WALL
BOUNDARIES

ROOF
 Underlies Frontal sinus and
Anterior cranial fossa
 Formed by-
◦ 1. Frontal bone (Orbital
plate)
◦ 2. Lesser wing of Sphenoid
 Triangular
 Faces downwards, and
slightly forwards
Left orbit

 Concave anteriorly, almost flat posteriorly
 The anterior concavity is greatest about 1.5 cm from
the orbital margin & corresponds to the equator of
the globe.
 Thin, transluscent and fragile (except the lesser
wing of the sphenoid)
ROOF

LANDMARKS
• 1. FOSSA FOR THE LACRIMAL GLAND-
 LOCATION:
behind the zygomatic process of the frontal bone
 CONTENTS:
lacrimal gland
some orbital fat
ROOF

2. TROCHLEAR FOSSA (FOVEA)
 LOCATION:
4 mm from the orbital margin
 CONTENTS:
insertion of tendinous pulley of Superior Oblique
o sometimes (≈10%) surmounted by a spicule of bone
(Spina trochlearis)
o Extremely rarely trochlea completely ossified
cracks easily
 SURFACE ANATOMY:
Palpable just within the supero-medial angle
ROOF

3. SUPRAORBITAL
NOTCH:
 LOCATION:
≈15 mm lateral to the
superomedial angle
 TRANSMITS:
- Supraorbital nerve
- Supraorbital vessels
 SURFACE ANATOMY:
- At the junction of lateral
2/3rd and medial 1/3rd
- About two finger breadth
ROOF
Right orbit

4. OPTIC FORAMEN:
LOCATION:
- Lies medial to superior
orbital fissure
- at the apex
- Present in the lesser wing
of sphenoid
TRANSMITS:
- Optic nerve with its
meninges
- Ophthalmic artery
ROOF
Left orbit

 Cribra orbitalia:
- apertures apparent on the medial side of anterior
portion of the lacrimal fossa
- for veins from diploë to the orbit
- Best marked in the fetus and infant
 Frontosphenoidal suture:
- between frontal and the lesser wing of the sphenoid
- usually obliterated in the adults
ROOF

Thin and fragile
Easily fractured by direct
violence (penetrating orbital
injuries)
Frontal lobe injury
ROOF

 Reinforced
- Laterally- greater wing of sphenoid
- Anteriorly- superior orbital margin
So, fractures tend to pass towards medial side
At junction of the roof and medial wall, the suture line lies
in proximity to cribriform plate of ethmoid
rupture of dura mater
CSF escapes into orbit/nose/both
ROOF

 Since the roof is perforated neither by major
nerves nor by blood vessels, so it can be easily
nibbled away in transfrontal orbitotomy.
ROOF

MEDIAL WALL
 Thinnest orbital wall
 Formed(Antero-posteriorly)
 1. Frontal process of
Maxilla
 2. Lacrimal bone
 3. Orbital plate of Ethmoid
 4. Body of the sphenoid
 Almost parallel to each other Left orbit

LANDMARKS
 LACRIMAL FOSSA:
- Formed by:
- frontal process of
maxilla
- lacrimal bone
- Boundaries:
- Anterior- anterior
lacrimal crest
- Posterior- posterior
lacrimal crest
Right orbit

- Dimensions-
- Length≈ 14 mm
- Depth≈ 5 mm
- Continuous below with bony nasolacrimal canal
- Content-
- Lacrimal sac
MEDIAL
WALL

 ANTERIOR LACRIMAL CREST*-
- upward continuation of the inferior orbital margin
- Ill defined above but well marked below
- Surface anatomy-
- Palpable along the medial orbital margin (anteriorly)
 POSTERIOR LACRIMAL CREST*-
- downward extension of the superior orbital margin
- Surface anatomy-
- Palpable along the medial orbital margin, posterior to
the lacrimal fossa
*significant landmarks in lacrimal sac surgery
MEDIAL WALL

 FRONTO ETHMOIDAL SUTURE LINE
- Marks the approximate level of ethmoidal sinus
roof
- Breach of this suture may open the frontal sinus,
or the cranial cavity
- Anterior and posterior ethmoidal foramina are
present in the suture line
MEDIAL WALL

 Anterior ethmoidal foramen
- 20-25 mm posterior from the anterior lacrimal crest
- Opens in the anterior cranial fossa at the side of the
cribriform plate of ethmoid
- Transmits-
- anterior ethmoidal nerve & vessels
MEDIAL WAL

 Posterior ethmoidal
foramen
- 32-35 mm posterior from
anterior lacrimal crest
- 7 mm anterior to the
anterior rim of optic
canal
- Transmits
- posterior ethmoidal
nerve & vessels
MEDIAL
WALL
Left orbit

Weber’s suture
 Lies anterior to lacrimal fossa
 Also known as sutura longitudinalis imperfecta
 Runs parallel to anterior lacrimal crest
 Branches of infraorbital artery pass through this
groove to supply the nasal mucosa
 Bleeding may occur from these vessels during
DCR surgeries
MEDIAL WAL

 Anteriorly located suture indicates predominance
of lacrimal bone
 Posteriorly located suture indicates the
predominance of maxillary bone*
*If maxillary component is predominant, it
becomes difficult to perform osteotomy to reach
the sac during DCR, because the maxillary bone
is very thick.
MEDIAL
WALL

 Medial wall extremely fragile (presence of
ethmoidal air cells and nasal cavity)
 Accidental lateral displacement of medial wall-
traumatic hypertelorism
 Medial wall provides alternate access route to
the orbit through the sinus
MEDIAL WALL

 Ethmoid
- Thinnest bone of the orbit
- Vascular connections with ethmoid sinus through foramina
- Inflammation in the ethmoid sinus spreads readily to the
orbit
 Tumours of the nasal cavity can breach the lamina
papyracea to involve the orbit
 Lacrimal bone can be easily penetrated during
endoscopic DCR
 During surgery, hemorrhage is most troublesome due to
injury to ethmoidal vessels.
MEDIAL WAL

FLOOR
• Shortest orbital wall
• Roughly triangular
• Formed by-
• Orbital plate of maxilla
(major)
• Orbital surface of
Zygomatic bone
(anterolateral)
• Orbital plate of Palatine
bone
Right orbit

 Bordered laterally by inferior orbital fissure and
medially by maxilloethmoidal suture
 Overlies maxillary sinus
FLOOR

LANDMARKS
Infraorbital
groove
Infraorbital
canal
Infraorbital
foramen
 ≈4 mm inferior to the inferior orbital margin
 Transmits
- Infraorbital nerve
- Infraorbital vessels
FLOOR

 BLOW OUT FRACTURES:
◦ Fractures of the orbital floor
◦ Infraorbital nerves and
vessels are almost invariably
involved
◦ Patient presents with
 Diplopia
 Restricted
movements(upgaze)
 Paresthesia
FLOOR

LATERAL WALL
 Formed by-
◦ 1. Zygomatic bone
◦ 2. Greater wing of
sphenoid
 Thickest orbital wall
 Separates orbit from-
◦ Middle cranial fossa
◦ Temporal fossa
 At an angle of about 90°
with each other
Right orbit

LANDMARKS
 LATERAL ORBITAL
TUBERCLE OF
WHITNALL:
- 4-5 mm behind the
lateral orbital rim
- 11 mm inferior to the
frontozygomatic
suture line
LATERAL
WALL
Right orbit

- Gives attachment to:
- Check ligament of lateral rectus
- Lockwood’s ligament
- Lateral canthal tendon
- The aponeurosis of the levator palpebrae
superioris
- Orbital septum
- Lacrimal fascia
LATERAL
WALL

 In resection of maxilla, the Whitnall’s tubercle is
spared, otherwise
Damage to Lockwood’s ligament
Inferior dystopia of eye ball
Diplopia
LATERAL
WALL

 SPINA RECTI LATERALIS:
- at the junction of wide & narrow portions of the
superior orbital fissure
- Produced by a groove lodging superior ophthalmic
vein
- Gives origin to a part of Lateral Rectus
LATERAL WAL

 ZYGOMATIC GROOVE:
- EXTENT:
- From the anterior end of the inferior orbital fissure to a
foramen in the zygomatic bone
- CONTENTS:
- Zygomatic nerve
- Zygomatic vessels
LATERAL WAL

 Lateral wall protects only the posterior half of the
eyeball, hence palpation of retrobulbar tumours is
easier.
 Frontal process of zygoma & zygomatic process of
frontal bone protect the globe from lateral trauma-
known as facial buttress area.
 Just behind the facial buttress area, is the
zygomaticosphenoid suture, which is the preferred
site for lateral orbitotomy.
LATERAL WAL

Anteriorly, superior margin of inferior
Orbital fissure joins suture between
zygomatic and greater wing of sphenoid
(line of relative weakness)
extends to frontozygomatic suture
Frequently involved in zygomatic bone
fracture
LATERAL WAL

SUPERIOR ORBITAL MARGIN
- formed by- Frontal bone
- concave downwards, convex forwards
- sharp in lateral 2/3rd ,rounded in medial 1/3rd
- at the junction- supraorbital notch (sometimes
foramen)*
- *Site for nerve block.

 Sometimes-
o Arnold’s notch/foramen
Present medial to supraorbital notch
Transmits
medial branches of supraorbital nerve & vessels
o Supraciliary canal
Near the supraorbital notch
Transmits
nutrient artery
a branch of supraorbital nerve to frontal air sinus
SUPERIOR ORBITAL
MARGIN

 SURFACE ANATOMY:
- Well marked prominence
- More prominent laterally than medially
- Eyebrow corresponds to the margin only in a part
- Head- under the margin
- Body- along the margin
- Tail- above the margin
SUPERIOR ORBITAL
MARGIN

LATERAL ORBITAL MARGIN:
- formed by
- zygomatic process of frontal
- the zygomatic bone
- strongest portion of margin

 Lateral orbital rim is recessed on its deep aspect ≈
0.75 cm above the rim margin to accommodate the
lacrimal gland
Prone to fracture
LATERAL ORBITAL
MARGIN

 Narrowest and weakest part- frontozygomatic
suture
Prone for separation following blunt trauma
LATERAL ORBITAL MAR

INFERIOR ORBITAL MARGIN:
 Formed by-
- Zygomatic
- Maxilla
- suture between the two is sometimes marked by a
tubercle- felt 4-5 mm above the infraorbital foramen
 SURFACE ANATOMY:
- Palpable as a sharp ridge, beyond which the finger can
pass into the orbit

 At the junction of lateral 2/3rd & medial 1/3rd just within
the rim- small depression- origin of Inferior oblique
Prone to fracture
Disruption of Inferior oblique
Diplopia
 Penetrating injuries may severe lacrimal passages
INFERIOR ORBITAL MAR

MEDIAL ORBITAL MARGIN:
- Formed by
- Frontal process of maxilla (anterior lacrimal crest)
- Lacrimal bone (posterior lacrimal crest)

 Orbital index= (Height/Width)X 100
1. Megaseme- ≥89% (Orbital opening-round)
2. Mesoseme- 82-88%
3. Microseme- ≤83% (Orbital opening-rectangular)

OPTIC CANAL
 Leads from the middle cranial fossa to the apex of
the orbit
 Orbital opening- vertically oval
 In the middle- circular (≈5mm)
 Intracranial- horizontally oval
 Length ≈ 8-12 mm
- Attained at 4-5 years of age
 Boundaries-
- Medially- Body of the sphenoid
- Laterally- Lesser wing of the sphenoid
Right orbit

 Directed- forwards, laterally and downwards
 Distance between
◦ Intracranial openings≈ 25mm
◦ Orbital openings≈ 30mm
 Transmits-
◦ Optic nerve & its meninges
◦ Ophthalmic artery
OPTIC
CANAL

 Processus falciformis: The roof of the canal
reaches farther forwards than the floor
anteriorly, while posteriorly, the floor projects
beyond the roof. Fold of dura mater filling the
gap in the roof is called Processus falciformis.
OPTIC CANA

 Optic nerve glioma or Meningioma may lead to
unilateral enlargement of Optic canal
OPTIC CANA
Strut view of Optic
Canal
(Normal)
CT-Scan showing lesion in Left
optic nerve

SUPERIOR ORBITAL FISSURE
 Also known as Sphenoidal
fissure
 Lateral to the optic foramen
at the orbital apex
 comma-shaped gap between the
roof and the lateral wall
 Bounded by- Lesser and greater
wings of the sphenoid
Left orbit

SUPERIOR ORBITAL
FISSURE
Right superior orbital fissure

 22 mm long
 Largest communication between the orbit and
the middle cranial fossa
 Its tip lies 30-40 mm from the frontozygomatic
suture
SUPERIOR ORBITAL
FISSURE

 Lateral superior part of the fissure is narrower
than the medial inferior part.
- At the junction of the two lies spina recti
lateralis
SUPERIOR ORBITAL
FISSURE

LANDMARK
 Annulus of Zinn
- Spans both superior orbital fissure & the optic
canal
- Gives origin to the four recti muscles
SUPERIOR ORBITAL
FISSURE

CLINICAL SIGNIFANCE
 Inflammation of the superior orbital fissure and
apex may result in a multitude of signs
including ophthalmoplegia and venous outflow
obstruction
TOLOSA HUNT SYNDROME
SUPERIOR ORBITAL
FISSURE

SUPERIOR ORBITAL SYNDROME
(Rochon-Duvigneaud syndrome)
Fracture at superior orbital fissure
Involvement of cranial nerves
Diplopia, Ophthalmoplegia,
Exophthalmos, Ptosis,
SUPERIOR ORBITAL
FISSURE

 Manner of involvement of nerves may be helpful in
predicting the site and extent of the lesion.
Divisions of III’rd nerve ± VI’th nerve
Annulus of Zinn (Purely intraconal lesion)
III’rd, IV’th and VI’th nerve
Entire length of the fissure involved
SUPERIOR ORBITAL
FISSURE

INFERIOR ORBITAL FISSURE
 Also known as sphenomaxillary
fissure
 Between floor and the lateral wall
 Bounded by-
oMedially- Maxilla and orbital
process of palatine
oLaterally- Greater wing of the
sphenoid
oAnterior aspect- closed by
Zygomatic bone Left orbit

 Transmits-
- Venous drainage from the inferior part of the
orbit to the pterygoid plexus
- neural branches from the pterygopalatine
ganglion
- the zygomatic nerve
- the infraorbital nerve
 Closed in the living by the periorbita & the
Muller’s muscle
 Serves as the posterior limit of surgical
subperiosteal dissection along the orbital floor
INFERIOR ORBITAL
FISSURE

CONNECTIVE TISSUE SYSTEM
 Periorbita
 Orbital septal system
 Tenon’s capsule

PERIORBITA (Orbital periosteum)
 Loosely adherent to the bones
 Sensory innervation by branches of V’th nerve
 Fixed firmly at
- Orbital margins (Arcus marginale)
- Suture lines
- Various fissures & foramina
- Lacrimal fossa

 Surgery in the orbital roof in the areas of
fissures and suture lines may be complicated
by cerebrospinal fluid leakage .
PERIORBITA

ORBITAL SEPTAL SYSTEM
 Includes the connective tissue septa which are
suspended from the periorbita to form a
complex radial and circumferential
interconnecting slings.
 These septa surround Extraocular muscles,
Optic nerve, neuro-vascular elements and the
fat lobules.

TENON’S CAPSULE
 Also known as Fascia bulbi or bulbar sheath.
 Dense, elastic and vascular connective tissue that
surrounds the globe (except over the cornea).
 Begins anteriorly at the perilimbal sclera, extends around
the globe to the optic nerve, and fuses with the dural
sheath and the sclera.
 Separated from the sclera by periscleral lymph space,
which is in continuation with subdural and subarachnoid
spaces.

CONTENTS OF THE ORBIT
 Eye ball
 Muscles
◦ 4 Recti
◦ 2 obliques
◦ Levator palpebrae superioris
◦ Muller’s muscle (Musculus orbitalis)
 Nerves
◦ Sensory- branches of V’th Nerve
◦ Motor- III’rd, IV’th & VI’th Nerve
◦ Autonomic- Nerves to the Lacrimal gland
◦ Ciliary ganglion
Left orbit

 Vessels
◦ Arteries-
 Internal carotid system- branches of ophthalmic artery
 External carotid system- a branch of internal maxillary
artery
◦ Veins-
 Superior ophthalmic vein
 Inferior ophthalmic vein
◦ Lymphatics-
 none
 Lacrimal gland
 Lacrimal sac
 Orbital fat, reticular tissue & orbital fascia
CONTENTS OF THE
ORBIT

 CILIARY GANGLION
- Peripheral parasympathetic
ganglion
- Lies between Optic nerve and
Lateral Rectus muscle
- ≈1cm anterior to the optic
foramen
- 3 posterior roots
- Sensory root
- Nasociliary Nerve
- Motor root
- Nerve to inferior oblique
- Sympathetic root
- Branches from internal
NERVES

SURGICAL SPACES
 SUBPERIOSTEAL SPACE:
◦ Between orbital bones and the periorbita
◦ Limited anteriorly by strong adhesions of periorbita to
the orbital rim

 PERIPHERAL ORBITAL SPACE (ORBITAL SPACE)
- Bounded:
- peripherally by periorbita
- internally by the four recti with their intermuscular
septa
- anteriorly by the septum orbitale
- Posteriorly, it merges with the central space
SURGICAL
SPACES

 CONTENTS:
 Peripheral orbital fat
 Muscles
◦ Superior oblique
◦ Inferior oblique
◦ Levator palpebrae superioris
 Nerves
◦ Lacrimal
◦ Frontal
◦ Trochlear
◦ Anterior ethmoidal
◦ Posterior ethmoidal
 Veins
◦ Superior ophthalmic
◦ Inferior ophthalmic
 Lacrimal gland
 Lacrimal sac
SURGICAL
SPACES

 CENTRAL SPACE
- Also known as muscular cone or retrobulbar space
- Bounded:
- Anteriorly by Tenon’s capsule
- Peripherally by four recti with their intermuscular septa
- In the posterior part, continuous with the peripheral orbital
space
SURGICAL
SPACES

 CONTENTS:
 Central orbital fat
 Nerves
◦ Optic nerve (with its meninges)
◦ Oculomotor
 Superior and inferior divisions
◦ Abducent
◦ Nasociliary
◦ Ciliary ganglion
 Vessels
◦ Ophthalmic artery
◦ Superior ophthalmic vein
SURGICAL
SPACES

 SUBTENON’S SPACE*
- Between the sclera and the Tenon’s capsule
- *Pus collected in this space is drained by incision of
Tenon’s capsule through the conjunctiva
- *Site for drug instillation
SURGICAL
SPACES

AGE RELATED VARIATIONS
 Infantile orbits are more divergent (≈115°) than
those of adults (≈40-45°)
 Orbital axes
- Lie in horizontal plane in infants
- slope downwards (≈15-20°) in adults

 Orbital fissures are relatively larger in childhood than
in adults (owing to the narrowness of the greater
wing of sphenoid)
 Orbital index- higher in children than in adults
(transverse diameter increases relatively more in
the later life)
 Interorbital distance is smaller in children- may give
false impression of squint
AGE RELATED
VARIATIONS

 Roof much larger than floor in infancy
 Optic canal has no length at birth- a foramen
- at 1 year of age≈ 4 mm
 Periorbita much thicker and stronger at birth than in
adults
AGE RELATED
VARIATIONS

 SENILE CHANGES-
 Holes, particularly in the roof due to absorption of
the bony wall
 Orbital fissures become wider
AGE RELATED
VARIATIONS

GENDER RELATED VARIATIONS
MALES
• Glabella &
supraciliary ridges
more marked
FEMALES
• Larger
• More elongated
• Rounder
• Upper margins
sharper
• Frontal eminences
more marked

TAKE HOME
MESSAGE…………………...
 Knowledge of orbital anatomy and its variations
helps to determine the pathology as well as the
site, direction and extent of the incision during
elective exploration of the orbit.
 It is also must for understanding the clinical
course and planning the management in cases
of accidental incisions/explorations.

Orbit

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