orbit

1. Orbit anatomy

2. Introduction
Orbit is the anatomical space bounded:
*Superiorly-Anterior cranial fossa
*Medially – Nasal cavity & Ethmoidal air cells
*Inferiorly –Maxillary sinus
*Laterally-Middle cranial fossa
Made up of 7 bones :
-Ethmoid
-Frontal
-Lacrimal
-Maxillary
-Palatine
-Spenoid
-Zygomatic

3. Gross anatomy
 Dimensions
 Depth ≈ 42 mm along medial wall
≈ 50 mm along lateral wall
 Intraorbital width – distance between medial margins of both
orbits ≈ 25 mm
 Extraorbital width – distance between lateral margins of both
orbits ≈ 100 mm
 Orbital index = (height / width) ×100
>89 – megasenes (orientals)
83 – 89 – mesosenes (caucasian)
< 83 – microsenes (nigros)
 Volume ≈ 30ml
-volume of orbit : volume of eyeball = 4.5:1

4.  Angulations – Between lateral wall & sagital plain ≈ 45˚
- Between visual axis & orbital axis ≈ 23˚
- Medial wall of both orbits are parallel to each
other
- Lateral wall of both orbits bears an angle of 90˚

5.  Contents of orbit:
Eyeball : 1/5 of orbit
Muscles : 4 Recti , 2 Oblique , LPS , Muller’s muscle
Nerves :II , III ,IV , VI , V1 (Lacrimal , frontal , nasociliary)
V2 (Infraorbital &zygomatic)
 Vessels :Ophthalmic artery & its br
infraorbital vessels
br of middle meningial artery
sup & inf ophthalmic vein
Orbital fat & reticular tissue& orbital Fascia
 Lacrimal Gland & Sac

6.  Walls of orbit :
i)Medial wall:
Quadranular
a)Frontal process of maxilla
b)Lacrimal bone
c)Orbital plate of ethmoid
Made up of
bone
d)Body of sphinoid
In anterior part
lacrimal fossa
bounded by
(d) (c) (b)
(a)
Anterior
lacrimal
crest
(maxilla)
Posterior
lacrimal
crest
(lacrimal bone)

7. Attachments behind post lacrimal crest are
* Horners muscle
* Septum orbitale
* Check lig of MR
Relations
Medially
a)Anterior ethmoid sinus
b)Middle meatus
c)Middle ethmoid sinus
d)Posterior ethmoid sinus

8. Orbital surface related to SO & MR ,in between two lies
• Ant & post ethmoidal nerve
• Intratrochlear nerve
• Terminal br of ophthalmic artery
Clinical application:
-Thinnest wall
-Ethmoiditis is commonest cause of orbital cellulitis due to
erosion of this wall especially in children.
-It is commonly erroded by chronic inflammatory lesion, cysts
and neoplasms originsting in adjuscent air sinuses.
-Injury to this wall causes troublesome haemorrhages d/t injury
to ethmoidal vessles.
-Easily fractured during injuries or orbitotomy operations.
-Medial wall is easily visualised in PAview of radiograph of skull

9. ii)Inferior wall
-Triangular
-Shortest
-Made up of
a) Medially - maxillary bone
b)Laterally - zygomatic bone
c)Posteriorly -Palatine bone

10. -Inferior orbital fissure separates posterior part of floor from
lateral
wall.
-Fissure  groove  canal Infraorbital foramena
(Infraorbital nerve & vessels)
-Relations:
Below  maxillary & palatine air sinuses
Above Inferior oblique & rectus muscle & nerve to IO.

11. -Clinical application:
* Commonly involved in blow out # & easily invaded by
tumours of maxillary antrum.
* Orbital floor can be appraoched by inferior orbitotomy i.e
antral approach.
* Blow out # - Infraorbital nerves & vessels are involved
- clinically  diplopia, restricted movements in up
gaze,
parasthesis & enophthalmos.

12. iii)Lateral wall :
-Triangular
- Made up of Anteriorly –(a) Zygomatic bone
Posteriorly –(b)Greater wing of sphenoid
(b)
(a)
-Spina recti lateralis – Bony projection on posterior part of
wall
gives attachment to some fibres of LR

13. -Lateral orbital tubercle of whitnall - Bony projection on
anterior part of wall  gives attachment to check lig of LR
-Separated from roof by sup orbital fissure
& from floor by
inferior orbital fissure.
-Relations:
Laterally in anterior part  temporal fossa
In posterior part  middle cranial fossa
Medially - LR , Lacrimal nerve & vessels , zygomatic nerve
& their communication.

14. -Clinical application :
*Lateral wall protects only post ½ of eyeball , anterior ½ is not
covered with bone .
*So , palpation of retroorbital tumours easier from lateral side
than nasal side.
*This wall is almost devoid of foramina , so its anterior ortion
can be easily broached without serious haemorrhages.
*Because of its advantageous anatomical position lateral orbital
surgical approach is popullar .
* Zygomatico-sphenoid suture is most important landmark on
creating a flap in Kronlein’s operation . Once this flap has been
turned , there is direct access to superolateral , inferolateral &
retrobulbar quadrants of orbit.

15. iv)Superior wall /Roof :
-Triangular
-Made up of Anteriorly –(a)Frontal bone
Posteriorly – (b)Laser wing of sphinoid
(a)
(b)

16. -Separates orbit from frontal sinus & anterior cranial fossa.
-Fossa for lacrimal gland –present in anterolateral part of roof
-Trochlear Fossa – present in medial part ,
- attachment for pulley of SO

17. -Relations :
Above Frontal lobe & meninges
Below Periorbita , frontal nerve , trochlear nerve,
LPS , SR , SO & Lacrimal gland
-Ant & post Ethmoidal canals: present at junction of roof &
medial wall

18. -Clinical significance:
*A sharp object injury through upper lid penetrates the roof &
may damage frontal lobe.
*Orbital roof anamolies or fractures can lead to pulsatile
exophthalmos.
* Since roof is neither perforated by major nerves nor vessels , it
can be easily nibbed away in transfrontal orbitotomy.

19.  Base of orbit:
- anterior open end of orbit.
- bounded by orbital margins i.e. ring of compact bone which
gives attachment to orbital septum.
- Divided into 4 margins (frontal)
i) Superior orbital margin:
- Formed by frontal bone.
- Lateral 2/3 is sharp & medial 1/3 is rounded.
- At this junction lies supraorbital notch transmiting
supraorbital nerves & vessels.
- About 10 mm medial to supraorbital notch is supratrochlear
groove
transmitting supratrochlear nerve & artery.

20. ii)Lateral orbital margin:
-Strongest
-Formed by zygomatic process of frontal bone & zygomatic
bone.
-It does not reach as anteriorly as medial margins.
iii)Inferior orbital margin:
-Formed by laterally  zygomatic bone
medially  maxilla
- Medially it continues with anterior lacrimal crest.
- 4-5cm below orbital margin in line with supraorbital notch
lies infraorbital foramena transmitting infraorbital nerve &
vessels

21. iv)Medial orbital margin:
- Formed by below anterior lacrimal crest (maxilla)
above frontal bone
frontal bone
(maxilla)

22.  Appertures at the base of orbit:
- Base of orbit is closed partly by globe , extraocular muscles
& their fascial expansions.
- These fascial expansions & sup and inferior oblique muscles
bound 5 orifices between them & orbital margins .
-These are the communications between orbital cavity & deep
portion of eyelid.
- Through them blood & pus passes out of orbit . Further
spread in lid is prevented by orbital septum.

23. i) superior apperture:
-comma shaped
-lies between roof & upper surface
of LPS
-Fat from superomedial lobe may
herniate through this apperture.
ii) Superomedial apperture:
-Vertically oval
-Lies between reflected tendon of superior oblique & medial
check ligament
-It transmits  Infratrochlear nerve ,
dorsal nasal artery
angular vein.

24. -Heniation of fat through this space is common cause of
lobulated prominence in old people.
iii) Inferomedial apperture:
-Vertically oval
-lies between medial check ligament & inferior oblique and
Lacrimal sac.
iv) Inferior apperture:
-Triangular
-Bounded by inferior oblique , arcuate expansion of inf
oblique & floor of orbit.

25. v) InferoLateral apperture:
-Vertically oval
-Lies between arcuate expansion of inf oblique ,Inf oblique
muscle & Lateral check ligament.

26.  Apex of orbit:
-Posterior end of orbit.
-Has 2 orifices
i)Optic canal:
- Connects orbit to middle cranial fossa.
-Transmits Optic nerve & surrounding meninges
Ophthalmic artery.
-Normal adult dimensions are attended by 4-5 yrs.
-Length ≈ 6-11mm
-Orbital end is vertically oval
Centre is circular
Cranial end is horizontally oval
- Optic nerve glioma & meningioma causes unilateral
enlargement of optic canal.

27. ii)Superior orbital fissure:
-Comma shaped
-Bounded by greater & lesser wing of
sphinoid.
-Fissure is divided into upper middle &
lower part by common tendinous
ring .

28. Structures Passing
Middle
-Nasociliary Nerve (V1)
Lower
-Inferior
- Oculomotor Nerve
- Abducent Nerve
Vein
-Sympathetic
Upper
-Superior ophthal. V.
ophthalmic
-Lacrimal nerve (V1)
- Frontal nerve (V1)
Plexus
- Trochlear nerve
-Reccurent br of

29. Periorbita:
-Periosteum lining orbital bones.
-Loosely adherant except at orbital margins, sup & inf orbital
fissures , optic canal, lacrimal fossa & at sutures.
-In optic canal dural sheath is adherant to periorbita.
-Arcus marginale: -thickened periorbita at orbital margins
-gives attachment to orbital septum.

30. -Lacrimal fascia: - periorbita at post lacrimal crest splits into 2
layers reunits at anterior lacrimal crest to enclose Lacrimal
sac.
-Tendinous ring of zinn:- Thickened periorbita at orbital apex
which gives attachment to 4 recti muscles.

31.  Orbital fascia:
-Thin connective tissue membrane lining various intraorbital
structures.
-Described under following structures
i)Fascia bulbi :
-Envelopes globe from from limbus to optic disc.
-Outer surface lies in contact with orbital fat posteriorly &
subconjunctival tissue anteriorly with which it merges at
limbus.
-Tenon’s capsule is seperated from sclera by Episcleral space
/ tenon’s space .
-Lower part of fascia bulbi is thickened forming asling on
which the globe rest k/a suspensory ligament of lockhood.
which extends from posterior lacrimal crest to lateral orbital
wall.

33. -stuctures piercing tenons capsule:
o Optic nerve - posteriorly
o Ciliary nerve & vessels -posteriorly
o Venae vorticosae –just behind equator
o Extraocular muscles - anteriorly ; where it becomes
conteneous with fascial sheaths of
muscles.
ii)Fascial sheaths of extraocular muscles:
-At a point where fascia bulbi is pierced by muscles , it sends
tubular reflections which clothes the muscle & continues as
perimysium.

34. iii)Fascial expansions of extraocular muscles:
 Lateral & medial check ligament:- Expansions of lateral &
medial rectus are strong & are attached to tubercles on
Zygomatic & Lacrimal bone respectively.
 Expansion of Superior Rectus is attached to LPS 
ensures synergestic action of two muscles.
Hence when SR makes eye to look up , the upper lid
is also raised.
In maximal levetor resection for ptosis surgery ,
hypotropia can be induced if these connections are not
severed.
 Expansion of Inferior rectus is attached to
capsulopalpabral fascia.
 Expansion from Superior oblique passes to trochlea.
 Expansion from Inferior oblique passes to lateral part of
roof & floor.

35.  Superior transverse ligament of whitnall:
-Condensation of superior sheath of
LPS & reflected tendon of superior
oblique.
-Extends from trochlear pulley to
lacrimal gland fossa.
- True check ligament of LPS.
 Suspensory ligament of fornices..(Sup & inf)
-Superior suspensory Lig  During ptosis surgery if this lig is
cut fornix conjuntiva can prolapse,
 Orbital septa.
-passes from periorbita to fascia bulbi.
-These provides specific channels for ophthalmic veins.

36. iv) Intermuscular septa / membrane:
-It is a Sheath of all 4 recti muscles are joined to each other by
facial membrane.
-It has divided orbital cavity & orbital fat into central &
peripheral part.

37.  Surgical spaces in orbit:
- Orbit is divided into 4 surgical spaces
- Importance of these spaces is that 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 )
1.Subperiosteal space.
2. Peripheral orbital space.
3.Central orbital space.
4. Subtenon’s space

38. 1. Subperiosteal space:
-Lies between orbital bone & periorbita.
-Tumours arising from bone separates periorbita from bone .
-Here periorbita acts as a effective barrier against spread of
tumour to eye.
-Tumours in this space are:  Dermoid cyst
Epidermoid cyst
Mucocoele
Subperiosteal abscess
 Myeloma
 Osteomatous tumour
 Hematoma
Fibrous dysplasia
.

39. 2.Peripheral orbital space:
- Lies between - periorbita at periphery
- extraocular muscles & their intermuscular septa
internally
- orbital septum anteriorlly.
-Posteriorly it merges with central space.
- Contents  Periorbital fat
SO , IO , LPS
 Lacrimal , frontal , trochlear, ant & post ethmoidal
nerve.
 superior & inferior ophthalmic vein
 Lacrimal gland & Lateral ½ of lacrimal sac.

40. -Tumours in this space are: Malignant lymphoma
 Capillary haemangioma of
childhood
 Intrinsic neoplasm of lacrimal
gland
Pseudotumours
-Tumours in this space are usually approached by anterior
orbitotomy & sometimes by lateral orbitotomy.
-Tumours in this space produce eccentric proptosis.

41. 3. Central orbital space:
- k/a muscle cone / retro-orbital space / posterior space.
- Bounded by - anteriorly tenon’s capsule
-posteriorly by 4 recti & intermuscular septa
- In posterior part ,space becomes continuous with peripheral
space.
-Content :
a) Nerves: -Optic nerve with meninges
- Sup & inf division of oculomotor nerve.
- Abducent nerve
- Nasociliary nerve
- Cilliary ganglion
b) Artery - Ophthalmic artery
c) Vein - Sup ophthalmic vein
d) Central orbital fat.

42. - Tumours of this space: Cavernous haemangioma of
adults
 Solitary neurofibroma
Neurolemoma
 Nodular orbital meningiomas
Optic nerve glioma
-Produces axial proptosis
-Tumours are approached through lateral orbitotomy.

43. 4. Subtenon’s space:
- Space around eyeball between sclera & tenon’s capsule
- Pus collection in this space is drained by incision on tenon’s
capsule through conjunctiva.

44.  Orbital fat & reticular tissue:
-It is divided by intermuscular septa into
*Central part *Peripheral part
- 4 lobules
superomedial
inferomedial
 superotemporal
inferotemporal

45. -Both becomes continuous with each other postereriorly.
-Benign encapsulated tumours do not alter the normal articular
structure
of reticular tissue except these are under great pressure.
-Malignant & infiltrative lesions like pseudotumours & endocrine
exophthalmos , this basic matrix may alter depending on
nature &
duration of lesion.

46. Thankyou.....