Call Girl In Pune 👉 Just CALL ME: 9352988975 💋 Call Out Call Both With High p...
Orbital anatomy
1. Orbital Anatomy
By- Dr. Kawshik Nag,
Resident,
Ophthalmology, Phase-A
Chittagong Medical College.
2. Anatomy Of Orbit
Quadrangular truncated
pyramidal in shape.
Bounded by-
• Superiorly- Anterior cranial
fossa
• Medially- Nasal cavity and
ethmoidal air sinuses
• Inferiorly- Maxillary sinus
• Laterally- Middle cranial fossa
and Temporal fossa.
3. Dimensions
Volume: 30cm3
Rim: Horizontally- 4cm
Vertically- 3.5cm
Intra orbital width: 2.5cm
Extra orbital width: 10cm
Depth: Medially- 4.2cm
Laterally- 5.0cm
Ratio of vol. of orbit : vol. of
globe: 4.5:1
4. Bony Orbit
Seven bones make
up the bony orbit :
Frontal bone
Zygomatic Bone
Maxillary bone
Ethmoid bone
Sphenoid bone
Lacrimal bone
Palatine bone
5. Walls Of The Orbit
The bony orbit has four
walls:
Medial wall
Lateral wall
Roof
Floor
6. Medial Orbital Wall
The medial wall is
formed from front to
back by the:
Frontal process of maxilla
Lacrimal bone
Orbital plate of the ethmoid
bone
Body of the sphenoid bone.
7. Medial Orbital Wall
Clinical applications:
• It is the thinnest wall of the orbit, so it is frequently fragmented as a
result of indirect blow out fractures and during orbitotomy operations.
• Frequently eroded by chronic inflammatory lesions, neoplasms, cysts.
• Medial wall provide alternate access route to the orbit through sinus.
• Haemorrhage can occur due to trauma to ethmoidal vessels.
• Accidental lateral displacemet of medial wall causes traumatic
hypertelorism.
8. Lateral Orbital Wall
Thickest and strongest.
Formed by two bones:
• Zygomatic
• Greater wing of sphenoid.
9. Lateral Orbital Wall
Clinical applications:
• The anterior half of globe is not covered by bone on lateral side.
Hence, palpation of retrobulbar tumours is easier from the lateral
side.
• The zygomatico-sphenoid suture is an important landmark in creating
the flap in lateral orbitotomy.
• It is the strongest portion of the orbit and needs to be sawed open in
lateral orbitotomy.
• Since lateral wall is almost devoid of foramina, bleeding is less.
10. Roof Of Orbit
Underlies frontal sinus and
anterior cranial fossa.
Formed by-
• Orbital plate of frontal bone
• Lesser wing of sphenoid.
Triangular.
Faces downwards and slightly
forwards.
11. Roof Of Orbit
Clinical applications:
• Thin and periorbita peels away easily.
• Objects piercing upper eyelid penetrate roof and damage frontal
lobe.
• In old age roof may be absorbed so that periorbital and duramater
comes into contact.
• Any trauma of dura mater and CSF escapes into orbit or nose or
both.
12. Floor Of Orbit
Shortest orbital wall.
Formed by:
• Maxillary bone- medially
• Zygomatic bone- laterally
• Palatine bone- posteriorly.
Triangular in shape.
Bordered laterallly by inferior
orbital fissure and medially by
maxilloethmoidal sinus.
Overlies maxillary sinus.
13. Floor Of Orbit
Clinical applications:
• Commonly involved in Blow
out fractures of the orbit.
Infra orbital vessels and
nerves almost always
involved.
• Diplopia is the main
symptoms of blow-out
fracture.
• Easily invaded by tumors of
the maxillary antrum.
Figure- Mechanism of blow-out fracture
from displacement of the globe itself into
the orbital walls. The globe is displaced
posteriorly, striking the orbital walls and
forcing them outward.
14. Base Of Orbit
The anterior open part.
Bounded by four orbital
margins-
• Superior orbital margin
• Inferior orbital margin
• Medial orbital margin
• Lateral orbital margin.
It gives attachment to the
septum orbitale.
15. Apex Of Orbit
Orbital apex is the posterior
end of the orbit.
Four orbital walls converge.
Two orifices:
• Optic Canal
• Superior orbital fissure
16. Optic Canal
It connects the orbit to the
middle cranial fossa.
It transmits:
• Optic Nerve
• Ophthalmic artery.
17. Superior Orbital Fissure
Structure passing:
Upper lateral part:
• Lacrimal and frontal nerves
• Trochlear nerve
• Superior ophthalmic vein
• Recurrent branch of
ophthalmic artery.
Middle part:
• Superior and inferior divisions
of occulomotor nerve
• Nasociliary branch of
ophthalmic division of
trigeminal nerve.
• Abducent nerve.
Lower medial part:
• Inferior ophthalmic vein.
18. Superior Orbital Fissure
Clinical applications:
• Radiographic enlargement of superior orbital fissure may
accompany pathologic processes,
Aneurysm
Meningioma
Choroidoma
Pituitary adenoma
tumours of orbital apex.
• When idiopathic inflammation involves the superior orbital fissure,
the “Tolosa Hunt syndrome” which is painful ophthalmoplegia
results.
19. Periorbita
Periorbita refers to periosteum
lining the orbitlal surface of the
bones of orbit.
Loosely adherent to the bones.
Fixed firmly at-
• Orbital margins
• Suture lines
• Various fissures and foramina
• Lacrimal fossa.
Applied Anatomy-
• Surgery in the orbital roof in
the areas of fissures and
suture lines may be
complicated by cerebrospinal
fluid leakage.
20. Orbital Fascia
It is a complex interwoven thin
connective tissue membrane
joining the various intraorbital
contents.
Parts-
• Fascia bulbi,
• Muscular sheaths,
• Intermuscular septa,
• Membranous expansions of
the extraocular muscles,
• Ligament of Lockwood.
22. Surgical Spaces In Orbit
Orbit is divided into 4 surgical spaces-
• Subperiosteal space
• Peripheral orbital space/ Extraconal space
• Central orbital space/ Intraconal space
• Subtenon’s space
23. Surgical Spaces In Orbit
Importance of these spaces-
• Most of the orbital tumours tends to remain with in a space in which
they are formed unless they are large or malignant or represents an
infiltrative process such as pseudotumour.
24. Subperiosteal Space
Lies between orbital bone and
periorbita.
tumours arising from bone
separates periorbita from
bone.
Here periorbita acts as a
effective barrier against spread
of tumour to eye.
25. Subperiosteal Space
tumours in this space are-
• Dermoids cyst
• Epidermoid cyst
• Mucocele
• Subperiosteal abscess
• Osteomatous tumour
26. Peripheral Orbital Space
Known as extraconal space.
Lies between periorbita at
periphery, extraocular muscles
and their intermuscular septa
internally and orbital septum
anteriorly.
Posteriorly it merges with
central space.
tumours in this space are
usually approached by anterior
orbitotomy and sometimes by
lateral orbitotomy.
27. Peripheral Orbital Space
tumours in this space produce eccentric proptosis.
tumours in this space are-
• Malignant Lymphoma
• Capillary haemangioma of childhood
• Intrinsic neoplasm of lacrimal gland
• Pseudotumours.
28. Central Orbital Space
Known as muscle cone/ retro-
orbital space/posterior space/
intraconal space.
Bounded by-
• Anteriorly tenon’s capsule
• Posteriorly by 4 recti and
intermuscular septa.
In posterior part, space
become continuous with
peripheral space.
29. Central Orbital Space
tumours of this space-
• Cavernous haemangioma of adults
• Solitary neurofibroma
• Neurolemoma
• Nodular orbital meningiomas
• Optic nerve glioma.
Produce axial proptosis.
tumours are approached through lateral orbitotomy.
30. Subtenon’s space
Space around eyeball between
sclera and tenon’s capsule.
Pus collection in this space is
drained by incision on tenon’s
capsule through conjunctiva.
31. Contents Of The Orbit
Eyeball
Fascia: Orbital and bulbar.
Muscles: Extraocular.
Vessels:
• Ophthalmic artery
• Superior and inferior ophthalmic
vein
• Lymphatics.
Nerves: Optic,Oculomotor,
Trochlear, Abducent, Branches of
ophthalmic nerves and
sympathetic nerves.
Ciliary ganglion
Lacrimal gland and lacrimal sac
Orbital fat.