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.
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
2. Introduction
ī Orbit is the anatomical space bounded:
*Superiorly-Anterior cranial fossa
*Medially â Nasal cavity & Ethmoidal air cells
*Inferiorly âMaxillary sinus
*Laterally-Middle cranial fossa
ī Made up of 7 bones :
-Ethmoid
-Frontal
-Lacrimal
-Maxillary
-Palatine
-Spenoid
-Zygomatic
3. Embryology
ī Derived from above âmesenchyme that encircles the optic vessicle
below & laterally â maxillary processes
medially - fronto nasal process
behind â orbitosphenoid.
ī Developes by ī Enchondral ossification
(part derived from base of skull)
ī Membrenous ossification
(rest all)
ī By 6 -7 th month laying down of bone starting with maxillary process
4. ī During this time optic vesicles which are 170 ÍĻ apart are
rotated anteriorly.
ī At birth â hemispherical
ī Growth corresponds to eyeball till puberty
5. Congenital anamolies
īą Craniosynostosis â premature closure of skull sutures
âĸ Crouzon syndrome â
- short AP diameter of skull
- mid facial hypoplasia
- prominent lower jaw
- shallow orbit
- hypertelorism
- V exotropia
7. īą Dermoid cyst
-MC orbital cystic lession
-Origin ī pouches of ectoderm
trapped in bony sutures
ī MC site âfrontozygomatic suture.
īą Cephalocoele
-Reflects orbital entrapment of
neuroectoderm
-MC site- Frontal & Ethmoid
- pathology-herniaton of brain
parenchyma into orbit.
8. īą Fibrous dysplasia
-Benign developmental fibro-oscious lesion
-Origin-arrest in maturation at woven bone stage
- Pathology âbone is replaced by fibrous tissue.
9. Gross anatomy
īą Dimensions
ī§ Depth â 42 mm along medial wall
â 50 mm along lateral wall
ī§ Intraorbital width â distance between medial margins of both
orbits â 25 mm
ī§ Extraorbital width â distance between lateral margins of both
orbits â 100 mm
ī§ Orbital index = (height / width) Ã100
>89 â megasenes (orientals)
83 â 89 â mesosenes (caucasian)
< 83 â microsenes (nigros)
ī§ Volume â 30ml
-volume of orbit : volume of eyeball = 4.5:1
10. ī§ Angulations â Between lateral wall & sagital plain â 45Ë
- Between visual axis & orbital axis â 23Ë
- Medial wall of both orbits are parallel to each
other
- Lateral wall of both orbits bears an angle of 90Ë
11. īą Contents of orbit:
ī Eyeball : 1/5 of orbit
ī Muscles : 4 Recti , 2 Oblique , LPS , Mullerâs muscle
ī Nerves :II , III ,IV , VI , V1 (Lacrimal , frontal , nasociliary)
V2 (Infraorbital & zygomatic)
ī Vessels :Ophthalmic artery & its br
infraorbital vessels
br of middle meningial artery
sup & inf ophthalmic vein
ī Orbital fat & reticular tissue& orbital Fascia
ī Lacrimal Gland & Sac
12. īą Walls of orbit :
i)Medial wall: a)Frontal process of maxilla
ī Quadranular b)Lacrimal bone
ī Made up of c)Orbital plate of ethmoid
bone
d)Body of sphinoid
ī In anterior part
lacrimal fossa
bounded by
(d) (c) (b)
(b)
Anterior Posterior
lacrimal lacrimal (a)
crest crest
(maxilla) (lacrimal bone)
13. ī Attachments behind post lacrimal crest are
* Horners muscle
* Septum orbitale
* Check lig of MR
ī Relations a)Anterior ethmoid sinus
Medially b)Middle meatus
c)Middle ethmoid sinus
d)Posterior ethmoid sinus
14. Orbital surface related to SO & MR ,in between two lies
âĸ Ant & post ethmoidal nerve
âĸ Intratrochlear nerve
âĸ Terminal br of ophthalmic artery
ī 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 PA view of radiograph of skull
16. -Inferior orbital fissure separates posterior part of floor from
lateral
wall.
-Fissure ī groove ī canal ī Infraorbital foramena
(Infraorbital nerve & vessels)
-Relations:
Below ī maxillary & palatine air sinuses
Above ī Inferior oblique & rectus muscle & nerve to IO.
17. -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 ī diplopia, restricted movements in up
gaze,
parasthesis & enophthalmos.
18. iii)Lateral wall :
-Triangular
- Made up of Anteriorly â(a) Zygomatic bone
Posteriorly â(b)Greater wing of sphenoid
(b)
(a)
-Spina recti lateralis â Bony projection on posterior part of
wall
ī gives attachment to some fibres of LR
19. -Lateral orbital tubercle of whitnall - Bony projection on
anterior part of wall ī 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 ī temporal fossa
In posterior part ī middle cranial fossa
Medially - LR , Lacrimal nerve & vessels , zygomatic nerve
& their communication.
20. -Clinical application :
*Lateral wall protects only post ÂŊ of eyeball , anterior ÂŊ 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 Kronleinâs operation . Once this flap has been
turned , there is direct access to superolateral , inferolateral &
retrobulbar quadrants of orbit.
21. iv)Superior wall /Roof :
-Triangular
-Made up of Anteriorly â(a)Frontal bone
Posteriorly â (b)Laser wing of sphinoid
(a)
(b)
22. -Separates orbit from frontal sinus & anterior cranial fossa.
-Fossa for lacrimal gland âpresent in anterolateral part of roof
-Trochlear Fossa â present in medial part ,
- attachment for pulley of SO
23. -Relations :
Above ī Frontal lobe & meninges
Below ī Periorbita , frontal nerve , trochlear nerve,
LPS , SR , SO & Lacrimal gland
-Ant & post Ethmoidal canals: present at junction of roof &
medial wall
24. -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.
25. īą 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.
26. 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 ī zygomatic bone
medially ī 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
27. iv)Medial orbital margin:
- Formed by below ī anterior lacrimal crest (maxilla)
above ī frontal bone
frontal bone
(maxilla)
28. īą 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.
29. 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 ī Infratrochlear nerve ,
ī dorsal nasal artery
ī angular vein.
30. -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.
32. īą 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 â 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.
33. 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 .
35. īąPeriorbita:
-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.
36. -Lacrimal fascia: - periorbita at post lacrimal crest splits into 2
layers ī 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.
37. īą 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.
-Tenonâs capsule is seperated from sclera by Episcleral space
/ tenonâs 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.
38.
39. -stuctures piercing tenons capsule:
o Optic nerve - posteriorly
o Ciliary nerve & vessels -posteriorly
o Venae vorticosae âjust 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.
40. iii)Fascial expansions of extraocular muscles:
ī Lateral & medial check ligament:- Expansions of lateral &
medial rectus are strong & are attached to tubercles on
Zygomatic & Lacrimal bone respectively.
ī Expansion of Superior Rectus is attached to LPS ī
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.
ī Expansion of Inferior rectus is attached to
capsulopalpabral fascia.
ī Expansion from Superior oblique passes to trochlea.
ī Expansion from Inferior oblique passes to lateral part of
roof & floor.
41. ī 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.
ī Suspensory ligament of fornices..(Sup & inf)
-Superior suspensory Lig ī During ptosis surgery if this lig is
cut fornix conjuntiva can prolapse,
ī Orbital septa.
-passes from periorbita to fascia bulbi.
-These provides specific channels for ophthalmic veins.
42. 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.
43. īą 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. Subtenonâs space
44. 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: ī Dermoid cyst
ī Epidermoid cyst
ī Mucocoele
ī Subperiosteal abscess
ī Myeloma
ī Osteomatous tumour
ī Hematoma
ī Fibrous dysplasia
.
45. 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 ī Periorbital fat
ī SO , IO , LPS
ī Lacrimal , frontal , trochlear, ant & post ethmoidal
nerve.
ī superior & inferior ophthalmic vein
ī Lacrimal gland & Lateral ÂŊ of lacrimal sac.
46. -Tumours in this space are: ī Malignant lymphoma
ī Capillary haemangioma of
childhood
ī Intrinsic neoplasm of lacrimal
gland
ī Pseudotumours
-Tumours in this space are usually approached by anterior
orbitotomy & sometimes by lateral orbitotomy.
-Tumours in this space produce eccentric proptosis.
47. 3. Central orbital space:
- k/a muscle cone / retro-orbital space / posterior space.
- Bounded by - anteriorly tenonâs 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.
48. - Tumours of this space: ī Cavernous haemangioma of
adults
ī Solitary neurofibroma
ī Neurolemoma
ī Nodular orbital meningiomas
ī Optic nerve glioma
-Produces axial proptosis
-Tumours are approached through lateral orbitotomy.
49. 4. Subtenonâs space:
- Space around eyeball between sclera & tenonâs capsule
- Pus collection in this space is drained by incision on tenonâs
capsule through conjunctiva.
50. īą Orbital fat & reticular tissue:
-It is divided by intermuscular septa into
*Central part *Peripheral part
- 4 lobules
ī superomedial
ī inferomedial
ī superotemporal
ī inferotemporal
51. -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.