Anatomy of the orbital cavity

1. The Orbital Cavity
Dr. Mohammad Dmour, M.D
Supervised by : Dr.Yehya AL-Zorqan
Ophthalmology Department.
Islamic Hospital.

3. Introduction
• The orbital cavities are a pair of large bony sockets that
contain the eyeballs, their associated muscles, nerves,
vessels, and fat, and most of the lacrimal apparatus.
• Each cavity is pear shaped ,and its apex is directed
posteriorly ,medially ,and slightly upward.
• The medial wall runs antero-posteriorly parallel to sagittal
plane ,the lateral wall diverges at angle of about
45degrees.
• Seven individual bones form the orbit (maxilla ,palatine
,zygomatic , sphenoid ,frontal ,ethmoid ,and lacrimal ).

5. O

6. Orbital dimensions
• Depth : 42 mm along medial
wall
• Depth : 50 mm along lateral
wall
• Base :
• Width 40 mm
• Ht 35 mm
• Intraorbital width : 25 mm
• Exrtraorbital width : 100 mm
• Orbital index :
(ht/width)X100
• Volume : 30 ml

7. Orbital margin

8. Orbital margin
• Quadrilateral in shape with rounded corners.
• In adult : wider than it is high .
• Supraorbital margin is formed by frontal bone .
(lat 2/3 sharp , med 1/3 rounded ). at the junction of two
area supraorbital notch or foramen for passage of
supraorbital vessels and nerve).
• infraorbital margin is formed (lat by zygomatic ,med by
maxilla).
• Lateral margin is the strongest part , formed (above by
frontal , below by zygomatic ).
• Medial margin is formed ( above by frontal , below by
lacrimal crest of maxilla).

9. Walls of the orbital cavity
• The Walls are
lined with
periosteum ,and
consist of a roof
,floor ,medial, and
a lateral wall.
• The Apex of the
orbital cavity is at
the medial end of
the superior
orbital fissure.

11. Walls of the orbital cavity
• Roof :
• Formed by the orbital plate of frontal bone and small
extent of lesser wing of sphenoid posteriorly.
• Anterolaterally there is slight depression ( lacrimal fosse)
for orbital part of lacrimal gland .
• The Roof is thin and fragile and in old age portions of roof
may be absorbed.
• The Roof separates orbital cavity from anterior crainal
fossa and frontal lobe.

12. CLINICAL SIGNIFICANCE

14. • Lateral wall :
• Is the thickest wall.
• anterior 1/3 is formed by zygomatic bone.
• posterior 2/3 is formed by greater wing of sphenoid.
• it is continuous with roof anteriorly but seperated
posteriorly by superior orbital fissure .
• On the anterior part of the wall , there is a projection , the
lateral orbital tubercle of whitnall. It give attachment to
the check ligament of the lateral rectus muscle and to the
suspensory ligament of the eyeball.
Walls of the orbital cavity

17. Walls of the orbital cavity
• Floor :
• Formed largely by orbital plate of maxilla , orbital
surface of zygomatic ,small orbital process of
palatine.
• Separate the orbital cavity from maxillary sinus.
• Floor is continuous with lateral wall anteriorly, but
seperated posteriorly by inferior orbital fissure .

18. APPLIED ANATOMY
• Commonly involved in
BLOW OUT FRACTURES OF
THE ORBIT.
•Easily invaded by tumors of the
maxillary antrum.

19. Walls of the orbital cavity
• Medial wall
• Thinnest orbital wall:0.2-0.4mm thick
• Majority of it is formed by Lamina
papyracea
• Formed by four bone from anterior to
posterior :
1. frontal process of maxilla,
2. lacrimal bone,
3. Orbital plate of ethmoid
4. body of sphenoid.
• Lacrimal groove: on anterior
part of medial wall ,for lacrimal sac ,
formed by lacrimal bone posterior ,frontal
process of maxilla anterior,bounded by
lacrimal crests, continuous below with
nasolacrimal canal.

20. APPLIED ANATOMY
1. Since it is the thinnest,ethmoiditis is the
commonest cause of orbital cellulitis, especially
in children.
2. Frequently eroded by chronic inflammatory
lesions,neoplasms,cysts.
3. It is easily fractured during trauma.
4. Hemorrhage can occur due to trauma to the
ethmoidal vessels.

23. Openings in the orbital cavity

25. 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

27. • Optic canal:
1.lies in the lesser wing of sphenoid.
2.is situated close to the apex of the orbit.
3.Measuring 4 to 10 mm long.
4.It connects the orbit to the middle cranial fossa .
5.related medially to body of sphenoid.
6. transmit optic nerve, ophthalmic artery with its
surrounding sympathetic plexus .

28. Openings in the orbital cavity
• Ethmoidal foramina:
1. lies in frontoethmoidal suture or in frontal bone.
2. anterior foramen open in anterior cranial fossa at lateral edge of
cribriform plate transmit anterior ethmoidal artery and nerve.
1. posterior foramen traverse ethmoidal bone , transmit posterior
ethmoidal artery and nerve.
• Zygomaticofacial and zygomaticotemperal
foramen:
1. lies on the lateral wall of orbit.
2. Zygomaticofacial foramen transmit Zygomaticofacial nerve.
3. zygomaticotemperal foramen transmit zygomaticotemperal nerve.

29. Relations of the bony orbit:
• Superior
anteromedially : frontal air sinus.
anterior cranial fossa .
• inferior
maxillary air sinus
• Lateral
anteriorly : temperal fossa.
posteriorly :middle cranial fossa.
• Medially
nasal cavity ,ethmoidal sinus , sphenoid sinus.

30. Orbital periosteum( orbital fascia(
• Is the periosteum of the bone that form the wall of orbit,
loosely attached to bone .
• At orbital margin, the periorbita is continuous with
periosteum on external surface of skull, give attachment to
the orbital septum.
• At lacrimal groove it splits to enclose lacrimal sac and
continue inferior to form periosteum of nasolacrimal canal.
• Posteriorly, around optic canal and medial end of superior
orbital fissure, it thickens to form a fibrous ring (common
tendinous ring).
• periorbita receive its sensory innervations from branch of
trigeminal nerve.

31. Orbital muscle (Muscle of Muller(
• Is a thin layer of smooth muscle
that bridge the inferior orbital
fissure .
• Nerve supply : sympathetic
nerves
• Apart from its possible effect on
the position of the eyeball in the
orbit, the muscle seems to be
mainly concerned with directing
facial venous blood to or away
from the cavernous sinus which
acts as a heat exchanger for
internal carotid blood.

32. Effect of age on orbital cavity
• At birth : Relatively large and ossified margins.
• Young children :
1. Look more lat than adult
2. Superior & inferior orbital fissure are wider, become
narrowed by growth of greater wing of sphenoid.
3. Distance between the orbit are small and increases
by growth of frontal& ethmoidal sinuses
• Old age :
Bony absorption >>> holes in roof , med & lat walls.

33. 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.

34. Resources:
1. Ocular anatomy by Richard Snell.
2. Anatomy and physiology of Eye by Khurana.