It's a presentation of Anatomy of Bony Orbit and its applied aspects. It's been made by compiling images from many sources and includes almost all the information needed for a postgraduate .

1. Dr. Ashish Gupta
JR1 Ophthalmology
IMS , BHU
Anatomy of Orbit and its Clinical
Importance

2. Introduction

4. Gross Anatomy – Shape
 7 bones forming
Orbit -
1. Frontal
2. Zygomatic
3. Maxilla
4. Lacrimal
5. Ethmoid
6. Sphenoid
7. Palatine
 Orbits are like a Quadrangular
Truncated Pyramids .
 Above - Anterior cranial fossa
 Below - Maxillary sinus
 Between them - Nasal cavity and
Ethmoidal air sinuses
 Laterally (from behind forwards) –
Middle cranial fossa and muscular
Temporal fossa
 Base - Orbital margin (Anterior
orbital aperture)
 Apex - Between Optic foramen and
medial end of Superior orbital

5. EMBRYOLOGY
 Bony Orbit develops around the eyeball , it is formed from
the Mesenchyme that encircles the optic vesicle (begining
at 6wks gestation). Ethmoid is the first bone to be laid down
at 6-8 wks .
 Orbit is derived from :-
1. Above – Mesenchyme encircling the optic capsule and
mesenchymal capsule of the forebrain.
2. Below and Laterally – Maxillary process
3. Medially – Frontonasal process
4. Behind – Orbitosphenoid
 All bones of the orbit have membranous ossification
except lesser wing of sphenoid (endochondral
ossification). They begin to ossify during the 3rd month .

7.  Initially the optic vesicles are positioned 170-180 apart ,
on opposite sides of the forebrain , only later they are
directed anteriorly.
 3 months of gestation – orbital axis form an angle
of 105 between them, At Birth – angle reduced to 45.
 Orbit growth corresponds to the growth of eyeball.
Although , eyeball reaches adult size by 3yrs of age ,
the orbit undergoes considerable change in shape and
grows progressively until puberty .

8. Clinical
 Failure of complete rotation – Hypertelorism
 Overrotation – Hypotelorism

9.  Malpositions in ossification of orbital bones may
result in reduced orbital volume and proptosis –
Crouzon Syndrome .

10.  d

11. Contents of Orbit
 Eyeball (1/5th of the total orbital volume).
 Muscles – Superior , Inferior , Medial and Lateral Rectus ,
Superior and Inferior Oblique , Levator Palpebrae
Superioris and Muller’s muscles of the orbit . Orbital
muscle of Muller ( musculus orbitalis ) .
 Nerves – Optic Nerve (2), Oculomotor Nerve (3) , Trochlear
Nerve (4) , Abducent Nerve (6) , branches of Ophthalmic
division of Trigeminal Nerve (5) [ Nasociliary , Lacrimal ,
Frontal ] , branches of Maxillary division of Vth nerve (
infraorbital , zygomatic) .
 Vessels – Ophthalmic Artery and its branches , Infraorbital
vessels , orbital branch of middle meningeal artery ,
Superior and inferior Ophthalmic vein .
 Orbital fat , reticular tissue and Orbital fascia.

20. Walls of the Orbit
 Medial wall
1. Frontal Process of Maxilla
2. Lacrimal Bone
3. Orbital Plate of Ethmoid Bone
4. Body of Sphenoid

21. Medial Wall
Anatomy
 Quadrilateral in shape , thinnest wall k/a Lamina
Papyracea .
 Anterior Part – Lacrimal Sac Fossa
bounded Anteriorly - Ant. Larimal Crest (thick) -
Maxillary bone
Posteriorly - Post. Larimal Crest (thin) –
Lacrimal bone
 Medial to Lacrimal fossa – Anterior Ethmoidal Sinus
(upper part) and Middle Meatus of nose (lower part) .
 Content of Lacrimal fossa – Lacrimal Sac (along with its
fascia) .
 Behind the posterior lacrimal crest –
1. Horner’s muscle (lacrimal fibres of orbicularis).

23. Relations of Medial Wall
 Medially (towards the nose) – Anterior , Middle
and Posterior Ethmoidal Sinus , Sphenoidal Sinus ,
Middle Meatus of the nose .
 Orbital wall of the medial wall – related to
Superior oblique muscle in the upper part (near the
roof) and Medial rectus muscle in the middle part .
• Between these muscles – Anterior ethmoidal and
posterior ethmoidal nerve , infratrochlear nerve and
terminal branch of the ophthalmic artery .

25. Clinical
Applications
 Ethmoiditis being the most common cause of Orbital
cellulitis , especially in children .
 Its frequently eroded by Chronic inflammatory lesion ,
cysts and neoplasms of the adjacent air sinuses .
 Easily fractured during injuries and during orbitotomy
procedures.
 During surgery along this wall , hemorrhage is most
troublesome due to injury of Ethmoidal vessels .
Medial palpebral ,Frontal, Dorsal nasal arteries also
pass forward near the medial wall .
 Easily visualised on PA radiographs of orbit .

30. Inferior Orbital Wall
(Floor)
 Triangular and Shortest .
 3 bones :-
1. Orbital surface of the Maxilla (Medially)
2. Orbital surface of Zygomatic (Laterally)
3. Orbital process of the Palatine (posteriorly) .
 Posterior part of the floor of the orbit is separated
from the lateral wall by the Inferior Orbital Fissure .
 Posteriorly the floor extends upto the posterior limit of
the maxillary sinus ; doesn’t extend upto the orbital
apex .
 Inferior orbital fissure >Infraorbital Groove > Canal >
Foramen.
 Transmits – Infraorbital nerve , artery and vein (which
connects the inferior ophthalmic vein to the facial

31. Relations
 Below – Maxillary sinus
 Above – Inferior rectus muscle , Inferior Oblique muscle , nerve to
inferior oblique .
 Inferior Oblique muscle arises just lateral to the Nasolacrimal
canal and it’s the only muscle that doesn’t originate from the
orbital apex .
Clinical Applications
 Orbital floor is thin (thinnest just medial to the infraorbital canal) ,
is most commonly involved in ‘Blow-Out Fractures’ and also is
easily invaded by tumors of the maxillary antrum .
 Triad of Blow Out Fracture – Tear Drop Sign on X ray , Infraorbital
Nerve Anesthesia , Double Diplopia ( due to entrapment of Inferior
rectus and Inferior oblique muscle)
 Best visualised with PA radiographs .
 Floor can be approached by Inferior Orbitotomy (Antral approach)
easily .

34. Blow Out Fracture

35. Lateral wall
 Thickest and strongest , Triangular in shape.
1. Anteriorly – Zygomatic bone
2. Posteriorly – Greater wing of sphenoid .
 Anteriorly – Zygomatic groove and foramina
(zygomatic nerve and vessels) .
 Lateral Orbital Tubercle of Whitnall (1mm below
the frontozygomatic suture) , Attachments :-
1. Check ligament of lateral rectus muscle
2. Suspensory ligament of the eyeball
3. Lateral palpebral ligament
4. Aponeurosis of Levator muscle .
 Posteriorly , lateral wall is separated from roof by
Superior orbital fissure and from floor by Inferior
Orbital fissure .

37.  Relations
 Laterally – lateral wall separates the orbit from temporal
fossa anteriorly and middle cranial fossa posteriorly .
 Medially – orbital surface is related to lateral rectus ,
lacrimal nerve and vessels , zygomatic nerve and
communication between the two.
 Clinical Applications
 Lateral wall protects only the posterior half of the globe ,
anterior half is not covered by bone laterally . Hence ,
palpation of retrobulbar tumors is easier from the lateral
side of eyeball than medial .
 Lateral Orbitotomy - Zygomaticosphenoid suture is an
important landmark in creating flap in Kronlein’s
operation . Cutting through this thin plate allows easy
outward fracture of bone. Surgeon has direct assess to
Superolateral , Inferolateral and retrobulbar quadrants

39. Roof
 Triangular , formed by :-
1. Orbital plate of Frontal bone (mainly)
2. Lesser wing of sphenoid (at apex).
 Anterolateral part – fossa for Lacrimal gland .
 Junction of roof and medial wall (close to orbital
margin) – Trochlear fossa (fovea for pulley of Sup.
Oblique) .
 Roof slopes backwards and downwards towards the
Apex , it ends at Optic Canal and Superior Orbital
Fissure.
 Relations
• Above – Frontal lobe (Anterior Cranial Fossa) ,
meninges ,frontal sinus .
• Below – Periorbita , Frontal nerve , LPS , Superior
Rectus , Superior Oblique , Trochlear nerve and

40. • Frontoethmoid suture line – Anterior and Posterior
Ethmoidal foramen , transmits branches of Ophthalmic
arteries and Nasociliary nerves into the ethmoid bone
and nose . These vessels are source of subperiosteal
hematoma following Orbital Trauma .
 Clinical Applications
• Periorbita can be easily peeled off from its
undersurface.
• A sharp object introduced into the orbit through upper lid
penetrates the roof and may damage the frontal lobe .
• On the cranial side, dura can be nibbled away easily in
Transfrontal Orbitotomy .
• Roof of Orbit fracture or Base of Anterior Cranial Fossa
Fracture – Racoon or Panda Eyes .

42. Base of Orbit
 Anterior open end is called base, bounded by Orbital
Margins. Orbital margins gives attachment to septum
orbitale .
 Superior Orbital margin – Orbital arch of frontal bone
 Lateral 2/3 rd sharp and medial 1/3rd is rounded ,
junction – Supraorbital notch – Supraorbital nerve and
artery .
 10mm medial to this notch is Supratrochlear groove –
Supratrochlear nerve and Artery .
Lateral Orbital margin - Strongest , formed by
Zygomatic process of the frontal bone and zygomatic
bone .
Inferior Orbital margin – Zygomatic bone (laterally) and
Maxilla (medially). Medially becomes continuous with
Ant. Lacrimal Crest .

43. Apex of Orbit
 Posterior end of the orbit where all four walls converge .
 Two Orifices – Optic Canal and Superior Orbital Fissure
(situated in the Sphenoid bone) .
Optic Canal -
• Connects Orbit to the middle cranial fossa .
• Transmits Optic nerve and Ophthalmic Artery .
• Optic nerve glioma and Meningioma – Unilateral
enlargement of the canal (detected on X rays) .
Superior Orbital Fissure –
• Comma shaped aperture , bounded by lesser and
greater wings of sphenoid .
• Divided into Upper lateral , Middle and Lower medial
parts by Common Tendinous Ring (for origin of recti) .

45. Periorbita
 Periosteum of orbital surface of the bones of orbit .
 Its loosely adherent to bone , can be easily striped
off but it is firmly adherent at Orbital margin , Superior
and Inferior Orbital fissures , Optic canal , the lacrimal
fossa and at the sutures.
 In the Optic canal , the dural sheath of the optic nerve
is closely adherent to the periorbita .
 At the Orbital margin , it is thickened to form Arcus
Marginale to which the septum orbitale is attached .
So , Trauma or Surgery in this area may be
complicated by CSF leak .
 At the Posterior lacrimal crest , it splits into two layers
which reunite at the anterior lacrimal crest enclosing
the Lacrimal Sac (in form of Lacrimal fascia) .
 At the Apex , it thickened to form the Common

47. Orbital Fascia
 Complex interwoven connective tissue joining various
Intraorbital contents .
 Fascia Bulbi / Tenon’s Capsule –
 Dense , elastic and vascular connective tissue that
envelopes the globe from the limbus to the optic nerve .
 Forms a socket in which the globe moves .
 Two layers lined by endothelium :
 Inner surface lies in close contact with the sclera (connected
by fine trabeculae).
 Outer surface lies in contact with orbital fat posteriorly and
with subconjunctival tissue anteriorly with which it merges
near the limbus .
 Tenon’s capsule is separated from the sclera by Episcleral
space (Tenon’s space) , which is readily injected . This type
of block is k/a Parabulbar Block .

48.  The lower part of fascia bulbi is thickened and takes part
in the formation of a sling or hammock on which the
globe rests k/a Suspensory ligament of Lockwood .
 Around the distal end of the optic nerve , the fascia is
fused with the dural sheath of optic nerve.
 It is pierced by :-
o Optic nerve
o Ciliary nerves and vessels
o Venae vorticosae (just behind the equator)
o Six extraocular muscles (anteriorly)
[ The extraocular muscles don’t perforate this capsule ,
but invaginate it, the fascia being reflected from their
surfaces , becoming fascial sheaths of these muscles] .

49.  Fascial Sheaths of Extraocular Muscles
 Fascial Expansions of Extraocular muscles
 Lateral and Medial Check Ligaments – Strong and
attached to orbital tubercle on zygomatic bone and to
the lacrimal bone respectively.
 Rectus muscle pulleys of Connective tissue and
smooth muscle fibres – located close to the equator of
the globe . Most deleveloped around Medial Rectus .
 Expansion of Superior Rectus muscle is attached to
LPS – ensures synergistic action .
• In maximal LPS resection for ptosis , hypotropia can
be induced if connections are not severed .

50.  Expansion from Inferior rectus muscle is attached to the
Capsulopalpebral fascia .
 Expansion from Superior Oblique paases upto trochlea.
 Expansion from Inferior Oblique passes to lateral part of
roof of orbit .
 Suspensory ligament of Lockwood – thickened sling
or hammock of fascial sheath extending from posterior
lacrimal crest to lateral orbital tubercle , on which rests
the eyeball .
• Formed by fusion of expansions from the muscular
sheaths of
1. Medial Rectus
2. Lateral Rectus
3. Inferior Rectus
4. Inferior Oblique
5. Thickened inferior part of Tenon’s Capsule .

51.  Superior Transverse ligament of Whitnall -
• Thickened band of Orbital fascia , extends from
Trochlear pulley to lacrimal gland and its fossa .
• Formed by condensation of the superior sheaths of
LPS joined medially by the sheath of reflected tendon
of Superior Oblique muscle .
• True Check Ligament of Levator muscle .
 Suspensory ligaments of the fornix –
• Superior liagment. – formed by the continuation
forward of fibrous tissue between the LPS and SR
muscles to the Upper fornix . During Ptosis surgery , if
this ligament is cut , fornix conjunctiva can prolapse .
• Inferior ligament – formed by continuation forward of
fibrous tissue of lower lid retractors to inferior fornix .

52.  Orbital Septa of elastic and collagenous tissue –
• Well developed in adults .
• These septa pass inward from the Periorbita to Fascia
bulbi , also pass to and between extraocular muscles
and provide supportive channels to ophthalmic veins .
 From the ant. end of the expansion of each extraocular
muscle , a fibrous band passes to conjunctival cul-de-
sac . Helps in retraction of conjunctival sac when these
muscles contract .
 Intermuscular Septa/ Membrane
• The sheaths of four rectus muscles are joined by a
fascial membrane called Intermuscular Septum .
• It divides the orbital cavity and orbital fat into central
and peripheral part .

58. Surgical Spaces
 Four Surgical Spaces in the Orbit – relatively self
contained , within each of which inflammatory
processes are contained for a considerable time
(unless they are large or malignant or infiltrative
process such as pseudotumor) . They should be
opened separately .
1. Subperiosteal space – between the bones of orbital
wall and periorbita .
2. Peripheral Orbital (extraconal) space – between
the periorbita and the extraocular muscles which are
joined by fascial connections (making a more or less
circular septum).
3. Central Intraconal space – cone shaped area
enclosed by the muscles (the muscle cone) .

61.  Subperiosteal Space –
 Potential space between the orbital bones and
periorbita , limited anteriorly by the adhesions of
periorbita to orbital rim .
 Forms an effective barrier against the spread of tumor
towards the eye.
 Some common lesions seen in this space –
1. Dermoid cyst
2. Epidermoid cyst
3. Mucocele
4. Subperiosteal Abscess
5. Myeloma
6. Osteomatous tumor
7. Hematoma
8. Fibrous dysplasia
 Diagnosis – Plain Xrays .

62.  Peripheral Orbital Space / Extraconal/ Anterior
Space –
• Bounded peripherally – Periorbita
• Internally – Four extraocular muscles with their
intermuscular septa
• Anteriorly – Septum Orbitale (including tarsal plates
and tarsal ligaments )
• Posteriorly – merges with the central space ( where
intermuscular septa are not present) .
• Tumors present in this area produce Eccentric
Proptosis and can be palpated .
• Common tumors found in this area are :-
1. Malignant Lymphoma
2. Capillary hemangioma of childhood
3. Intrinsic neoplasms of the lacrimal gland
4. Pseudotumors

63.  Contents –
1. Peripheral Orbital Fat
2. Superior Oblique , Inferior Oblique , LPS
3. Lacrimal , Frontal , Trochlear , Ant. and Post.
Ethmoidal nerves
4. Superior and Inferior Ophthalmic Veins
5. Half of Lacrimal Sac
 Central (Intraconal) Space / Muscular cone /
Posterior / Retrobulbar Space –
 Bounded anteriorly – Tenon’s capsule lining the back
of the eye
 Peripherally – Extraocular rectus muscles (along with
their intermuscular septa)

64.  Contents –
1. Optic nerve and its meninges
2. Superior and Inferior divisions of Oculomotor nerve
3. Abducent nerve
4. Nasociliary nerve along with ciliary ganglion
5. Ophthalmic artery
6. Superior Ophthalmic vein
7. Central orbital fat
 Tumors seen – Removed – Lateral
orbitotomy
1. Cavernous hemangioma of the adults
2. Solitary neurofibroma
3. Neurilemomas Axial Proptosis
4. Nodular Orbital Meningioma
5. Optic nerve glioma

65.  Sub-Tenon’s space –
 Between sclera and tenon’s capsule.
 Pus collected in this region is drained by incision of
Tenon’s Capsule through Conjunctiva .

67. Orbital Fat and Reticular
Tissue
 Most of the orbital cavity is occupied with Orbital Fat ,
extends from Optic nerve to orbital wall and from the
apex to septum orbitale .
 The fat lobules lies in a web of reticular tissue , which
forms the framework of the orbital fat anchoring it to
the orbital fascia called as Orbital reticulum .
 Orbital fat is divided into Central and Peripheral parts
by Intermuscular septa . Posteriorly peripheral and
central parts are continuous with each other k/a Apical
Part.
 Peripheral fat has four lobules – Superomedial ,
Superolateral , Inferomedial , Inferolateral .
 They are not very inert , they may become very
reactive . Therefore , lesser the disturbance of these
structures during orbitotomy , the better the functional

68. Apertures at the Base of
Orbit
 The fascial expansions of extraocular muscles and the
two oblique muscles bound about 5 orifices between the
orbital margin and globe.
 Fat may herniate through these orifices from the orbit to
come into contact with septum orbitale .

69.  Superior Aperture –
 Comma shaped aperture between roof and upper
surface of LPS .
 Fat may herniate from the superomedial lobe to form
retroseptal roll , which serves as an imp. landmark
during LPS resection surgery for ptosis.
 Superomedial Aperture –
 Vertically oval , lies between reflected tendon of SO
muscle and Medial Check Ligament .
 Infratrochlear nerve , Angular Vein and Dorsal Nasal
artery pass through this aperture.
 Herniation of fat through this is a common cause of
lobulated prominence in old people .

70.  Inferomedial Aperture –
 Vertically oval , lies between Medial check ligament ,
origin of Inferior Oblique and the lacrimal sac .
 Inferior Aperture –
 Triangular , bounded by Inferior Oblique muscle ,
Arcuate expansion of Inferior Oblique muscle and floor
of orbit .
 Inferolateral Aperture –
 Small oval , between Arcuate Expansion of the
Inferior Oblique muscle and Lateral Check Ligament .

71. References