The orbit is a bony cavity containing the eyeball and surrounding structures. It is formed by 7 bones and has walls, openings, dimensions, and contents described in detail. Key structures include the extraocular muscles originating from the common tendinous ring, three surgical spaces containing different anatomical parts, and openings like the optic canal transmitting nerves and vessels. Damage to the thin bones can impact surrounding structures like the brain or cause diplopia.

1. THE ORBIT
Birkha Bogati
1st Batch
Optometry & Vision Science
NAMS, NEH

2. The orbit

3. Orbit
• A pair of bony cavity
of skull
• Contains eyeball,
EOM, nerves, fats,
vessels & most of the
lacrimal apparatus.
• Pear shaped with its
apex extending
posteriorly, medially
and slightly upward.
• Stalk lies within the
optic canal.

4. Formation
• Bony orbit is formed from
mesenchyme that encircles
the optic vesicle beginning
as early as the 6 week of
embryonic stage.
• During this time optic
vesicle 170˚ apart rotates
anteriorly.
• Each orbit is formed by
seven bones (Frontal,
Ethmoid, Lacrimal, Palatine,
Maxilla, Zygomatic &
Sphenoid.

5. Shape
• The two orbits are quadrangular truncated
pyramids situated between anterior cranial fossa
above & the maxillary sinuses below.

6. • Medial walls of the two
orbits are parallel to each
other. They are in
contact with the ethmoid
& sphenoid sinuses.
• Lateral wall of each
orbit lies at an angle of
45° to the medial wall.
The lateral walls of the
two orbits are at 90° to
each other. It separates
the orbit from the medial
cranial fossa posteriorly
& the muscular temporal
fossa anteriorly.

7. Orbital dimensions
 Vol. about 30 cc.
 Orbital entrance about
height = 35 mm
width = 45 mm
 Depth varies from 40-45 mm along the medial wall
& about 50 mm along the lateral wall
 Distance from post globe to optic foramen=18mm
 Length of orbital segment of optic nerve= 25-30mm.
This allow for significant forward displacement of
the globe without excessive stretching of the ON.

8. Walls of the orbit
• Roof or vault of the Orbit
 Orbital plate of frontal
bone & lesser wing of
sphenoid bone
 Landmarks: frontal air
sinus ,lacrimal gland
fossa, spine for the
pulley of superior
oblique muscle
 Roof separates the
orbital cavity from the
anterior cranial fossa and
frontal lobe of cerebral
hemisphere.

9. Applied anatomy
The roof It is located subjacent to the ant. cranial
fossa & frontal sinus. A defect in the orbital roof
causes pulsatile proptosis as a result of transmission
of cerebrospinal fluid pulsation of the orbit
 Mucocele form the frontal sinus extends form the
sinus to the orbital cavity
 Sticks, pointed metal objects may pierce the thin roof
and enter the cranial cavity and the frontal lobe of
the brain

10.  Fracture of superior margin may damage or displace
the trochlea and producing symptoms of superior
oblique palsy.
 Roof of the orbit is fragile and in old age portions of
the roof may be absorbed .

11. Medial orbital wall
Thinnest wall of orbit
formed by 4 bones:
• Frontal process of
maxillary bone
• Lacrimal bone
• Orbital plate of
ethmoidal bone
• Small part of the body
of sphenoid bone

12. Applied anatomy
– The lamina papyracea perforated by numerous
foramina for nerves & blood vessels. Orbital cellulitis
is therefore frepuently 2° to ethmoidal sinusitis

13. Orbital floor
Floor of orbit: composed
of 3 bones:
• Maxillary bone
• Palatine bone
• Orbital plate of
zygomatic

14. APPLIED ANATOMY
 Tumors of the maxillary sinus extend superiorly into
the orbital cavity n causes proptosis.
 Frequent “blow-out” fracture involving maxillary
sinus causes the floor of the orbital cavity entrap
inferiorly into the maxillary sinus, also causes
displacement of the eyeball inferiorly, results
diplopia.
 The fracture may injure the infraorbital nerve,
resulting hypoesthesia of the skin of the cheek.

15. Lateral Orbital Wall
Thickest & strongest
orbital wall formed by:
 Zygomatic bone
 Greater wing of
sphenoid bone
 Landmarks: tubercle of
Whitnall
 Located adjacent to the
temporal fossa and the
middle cranial fossa

16. APPLIED ANATOMY
Lateral wall
 Vulnerable to lateral trauma since it protrudes beyond
lateral orbit margin
 Fracture to the lateral margin involving the zygoma
results in depression in prominence of the cheek

17. OPENINGS INTO THE ORBITAL CAVITY
• Optic canal
• Supraorbital fissure /
notch
• Inferior orbital
fissure
• Ethmoidal foramens
• Zygomaticofacial
foramen
• Zygomaticotemporal
foramen

18. OPTIC CANAL
 Lies in the lesser wing
of sphenoid bone
 Related medially to the
body of sphenoid
 Situated close to apex
of orbit
 Connects the middle
cranial fossa with
orbital cavity
 Transmits the optic N,
ophthalmic A &
sympathetic fibers from
carotid plexus.

19. The superior
orbital fissure
A slit between
the greater &
lesser wings of
the sphenoid
bone through
which pass
important
structures from
the cranium to
the orbit.

20. INFERIOR ORBITAL
FISSURE
 Lies between the greater
wing of sphenoid &
maxillary bone
 Connects the pterygopalatine
& infratemporal fossa with
orbital cavity
 Transmits the maxillary N.
 Also transmits:
 Zygomatic N
 Branches of
pterygopalatine ganglion
 Inferior ophthalmic vein

21. Applied anatomy
Superior orbital fissure
– Inflammation at the superior orbital fissure & orbital
apex may therefore result in a multitude of signs
including ophthalmoplegia & venous outflow
obstruction resulting in edema of the lids & proptosis

22. ETHMOIDAL FORAMENS
• Lie in the frontoethmoidal
suture or in the frontal bone
• Situated where the roof joins
the medial wall
Anterior ethmoidal foramen:
 Opens into the ant. cranial
fossa at the lat. edge of
cribiform plate of ethmoidal
bone
 Transmits the ant ethmoidal
N & A.
Posterior ethmoidal foramen:
 Transmits the post.
ethmoidal N & A

23. ZYGOMATICOTEMPORAL FORAMEN
• Lies above
zygomaticofacial
foramen close to
sphenozygomatic
suture
• Transmits
zygomaticotemporal N.

24. ZYGOMATICOFACIAL FORAMEN
• Small foramen lie on the
lateral wall of orbit
• Lies close to junction of
lateral wall & floor
• Transmits
zygomaticofacial nerve

25. SUPRAORBITAL FORAMEN/ NOTCH
 Located at the medial
third of superior margin
of orbit
 Transmits:
- Supraorbital N & blood
vessels
- A branch of
Ophthalmic div (V1) of
cranial nerve V
(Trigeminal)

26. PERIORBITA
• The periosteal covering of the orbital bones
• Loosely adherent to the bone except at the orbital
margin, sutures, foramina, fissures and canals
• At the orbital apex, it fuses to the duramater covering
the optic nerve
• At the orbital margin, It gives rise to a sheet that
enter the eye lid to form orbital septum.
• At the lacrimal groove it splits to enclose the lacrimal
sac that continuous inferiorly to form the periostem of
the nasolacrimal canal .

27. • Posteriorly, around the optic canal and the
medial end of the superior orbital fissure the
periorbita is thicker to form a fibrous ring the
common tendinous ring, which gives origin to
the tendons of the four rectus muscles.
• Supplied by the sensory nerves of the orbit
from the branch of the cranial nerve V.

28. RELATIONS OF THE BONY ORBIT
Superior relation:
 Roof formed by the orbital bone, contains between its
two lamina anterio-medially—the frontal air sinus.
 Occasionally the ethmoid air cells also invade the roof.
 Superior to the roof are meninges and the frontal lobe of
the cerebral hemisphere.
Inferior relation:
• inferior to the floor lies the maxillary sinus.
• The infra orbital nerve and the blood vessels lie within
the infraorbital canal .

29. Lateral relation: Anteriorly the lateral wall
separates the orbital cavity from temporal
fossa and posteriorly from the middle cranial
fossa, the meninges and the temporal lobe of
the cerebral hemisphere.
Medial relation: Medial wall separates the
orbital cavity from anterior to posterior from
the nasal cavity, ethmoidal sinuses and the
sphenoidal sinus

30. Orbital fat
• Most of the orbital cavity is occupied by orbital fat
• Extends from the optic nerve to the orbital wall &
from the apex to the septum orbitale.
• Divided into central & peripheral parts by the
intermuscular septa.
• If surgical spaces of orbit are considered five, then the
orbital fat can be divided into three parts: peripheral,
central & apical

31. Applied anatomy
• Benign tumors do not alter the normal structure of
reticular tissue & fat, except that these structures are
under great pressure & when the periorbita has been
opened, bulge more persistently into the operative
field.
• In case of malignant tumors & infiltrative lesions like
pseduo-tumors & endocrine exophthalmos this
structures may alter depending on the nature &
duration of the lesion.
• Lesser the disturbance of these structures during
orbitotomy, the better the functional & cosmetic
results.

32. EXTRAOCULAR MUSCLES
• All of the EOM except IO
originate at the orbital apex.
• 4 Rectus muscles originate
from annulus of zinn.
• The LPS muscle arise above
the annulus on the lesser
wing of the sphenoid.
• IO muscle originates from the
shallow depression on the
orbital plate of maxilla just
lateral to the lacrimal sac.

34. Spaces in the orbit
Surgically there are four
spaces in the orbit.
They are:
1. Sub –periosteal
space
2. Peripheral space
3. Central space
4. Tenon's space

35. 1. Sub-periosteal space
• Between the bones of orbital wall & the periorbita.
• The periosteum is detachable in most parts except at
its attachment at the margin, roof & fissures
2. Peripheral space (extraconal)
• Between periorbita and extraocular muscles
• Is limited anteriorly by the check ligaments and
posteriorly by the common tendinuos ring and
periosteum at the optic foramen.
• contain lacrimal gland, branches of trigeminal
(frontal, infraorbital, and nasociliary) and trochlear
nerves, lacrimal and infraorbital vessels, ophthalmic
veins and part of ophthalmic artery.
• collection of the fluid in the space may exude thru'
the orbital septum & lead to edema of eyelid.

36. 3.The central space (Intraconal space)
 A cone shaped area enclosed by 4 rectus muscles &
their fascial expansions.
 Anteriorly the space is limited by the posterior
aspect of the eyeball
 Laterally by muscles and their fascial sheaths
 Posteriorly by the common tendinous origin of
muscles at the apex of the orbit
 Contains optic nerve and its meningeal coverings,
superior and inferior divisions of oculomotor nerve,
abducent nerve, ophthalmic artery, superior
ophthalmic vein and nasociliary nerve.
 The presence of any tumor or fluid in this space
usually results in Axial proptosis.

37. 4. The Tenon's space
– Between Tenon's capsule and the sclera
– A potential space around the globe
– Contains insertions of the tendon of extraocular
muscles, nerves and vessels piercing the eyeball
and loose reticular tissues.

38. Lesions

39. Blood supply
• Ophthalmic artery
• Superior ophthalmic
vein and inferior
opthalmic vein.
Lymphatic Drainage
– Lateral - superficial
pre auricuar nodes
– Medial –
submandibular nodes

40. Nerve supply:
Sensory innervation by
ophthalmic and
maxillary division of
the cranial nerve V
Motor innervation by
cranial nerve III,IV,VI
and VII
Sympathetic innervation by
plexus around the
internal carotid artery.
Parasympathetic innervation
by ciliary ganglion .

41. References
• Jack j Kanski clinical ophthalmology
• AAO
• Parson’s disease of the eye
• AK Khurana Anatomy & Physiology of the
Eye
• Internet sources

42. Thank you for
your attention