Anatomy of Orbit

1. Dr Ashma Shrestha
1st Year Resident
LEI, NAMS
1

2.  Introduction
 Development of orbit
 Bony anatomy
 Orbital fissures and canals
 Surgical spaces in orbit
2

3.  Pear shaped bony cavity containing globes, extra ocular
muscles, nerves, fat and blood vessels
 Above: Anterior cranial fossa
 Below: Maxillary sinus
 Lateral: Temporal and middle cranial fossa
 Medial: Nasal cavity and ethmoidal air cells
3

4.  Begins at 6 weeks of gestation
 Derived from cranial neural crest cells which expands to form:
 Frontonasal process
 Maxillary process
4

5.  Lateral frontonasal process forms the medial wall of orbit
 Maxillary process forms inferior and lateral wall of orbit
 Superior wall is formed from mesenchymal capsule of forebrain
5

6.  Bones differentiate during 3rd month and later undergo
ossification
 Ossification by endochondral or membranous type
 Frontal, zygomatic, maxillary and palatine bone intramembranous
ossification
 Sphenoid bone endochondral and intramembranous ossification
 Growth of orbit corresponds with growth of eyeball
6

7.  Infantile orbit are more divergent
 At adult =68º
7

8. Shape Height Width Index
Fetus Oval 14mm 18mm 77.7
Newborn Round 27mm 27mm 100
7 years Quadrilateral 28mm 33mm 84.4
Adult Quadrilateral 35mm 40mm 89.2
8

9. Depth Along medial wall- 42mm
Along lateral wall-50mm
Base Width-40mm
Height- 35mm
Intraorbital
width
25mm
Extraorbital
width
100mm
Volume 29-30ml
Orbital Index
>89 Megasemes
83-89 Mesosemes
<83 Microsemes
9

10. 10
 Frontal bone
 Lacrimal bone
 Ethmoid bone
 Sphenoid bone
 Zygomatic bone
 Maxillary bone
 Palatine bone

11. 11

12.  Formed by:
 Triangular orbital plate of frontal bone
 Lesser wing of sphenoid
 Marked anteriorly and flatter posteriorly
12

13.  Above:
 Frontal lobe of cerebrum and meninges
 Frontal sinuses
 Below:
 Periorbita
 Frontal nerve, trochlear nerve
 Levator palpebrae superioris, superior rectus, superior oblique
 Lacrimal gland
13

14.  At junction of roof and medial wall:
 Anterior ethmoidal canal through which passes anterior ethmoidal
vessels and nasociliary nerve
 Posterior ethmoidal canal through which passes posterior ethmoidal
nerve and vessels
 At junction of roof with lateral wall:
 Superior orbital fissure
14

15.  Lacrimal fossa
 Trochlear fossa
 Frontosphenoidal suture
 Supraorbital notch
 Cribra orbitalia
15
Cribra orbitalia

16.  Fossa for lacrimal gland
 Located behind zygomatic process of frontal bone
 Contains : lacrimal gland some orbital fat
 Trochlear fossa
 Small depression close to fronto lacrimal suture, about 4mm from
orbital margin
 Insertion of tendinous pully of superior oblique
 Sometimes ligaments get ossified forming a spicule of bone –spina
trochlearis
 Supraorbital notch
 Junction of lateral 2/3rd and medial 1/3rd
 Transmits: supraorbital nerve and vessels
16

17.  Frontosphenoidal suture
 Between frontal and lesser wing of sphenoid
 Usually obliterated in adults
 Cribra orbitalia
 Apertures apparent on medial side of anterior portion of lacrimal
fossa
 It allows veins to pass from diploe to orbit
 Marked in fetus and infant
17

18.  It is thin and fragile except lesser wing of sphenoid so
penetrating wound of upper lid may cause its fracture and
injury to frontal lobe
 Fracture of superior margin may damage or displace trochlea
producing symptoms of superior oblique palsy
 Mucocele from frontal sinus extends to orbital cavity
 It can easily nibbed away in transfrontal orbitotomy
18

19.  Triangular in shape
 Formed by:
 Orbital plate of maxilla medially
 Orbital surface of zygomatic bone laterally
 Orbital process of palatine bone posteriorly
19

20.  Above:
 Related to inferior rectus muscle , inferior oblique muscle
 Below:
 Related to maxillary air sinus
 Palatine air cells
20

21.  Infraorbital foramen located below the infraorbital rim
 Transmits infraorbital nerve, infraorbital artery and vein
21

22.  Commonly involved in blow-out fractures
 Break in orbital floor  herniation of ocular content into
maxillary sinus  enopthalmus
 Fracture may injure infraorbital nerve resulting in hypoesthesia
of skin of cheek and upper teeth on side of injury
 Invaded by tumors of maxillary antrum and cause non-axial
proptosis
22

23.  Thickest and strongest orbital wall
 Formed by:
 Anteriorly by orbital surface of zygomatic bone
 Posteriorly by orbital surface of greater wing of sphenoid
23

24.  Lateral wall separates orbit anteriorly from temporal fossa and
muscle
 Posteriorly from middle cranial fossa and temporal lobe of
cerebrum
 Orbital surface is related to lateral rectus, lacrimal nerve and
vessels, zygomatic nerve and communications between
zygomatic and lacrimal nerves
24

25.  Tubercle of Whitnall
 Zygomatic groove and foramen
 Spina recti lateralis
25

26.  Tubercle of Whitnall provides attachment to:
 Check ligament of lateral rectus muscle
 Suspensory ligament of eyeball
 Aponeurosis of levator palpebrae superioris
 Zygomatic groove and foramen
 Passes zygomatic nerve and vessels
 Spina recti lateralis
 Small bony projection on posterior part
 Gives origin to a part of lateral rectus muscle
26

27.  Protects only posterior half of eyeball; palpation of retrobulbar
tumors is easier from lateral side
 Devoid of foramina – decreased chance of hemorrhage during
surgery
 Zygomatico- sphenoidal suture is an important landmark in
creating flap in Kronlein’s operation
27

28.  Thinnest , quadrilateral in shape
 Formed by:
 Frontal process of maxilla
 Lacrimal bone
 Orbital plate of ethmoid
 Body of sphenoid
28

29.  Medial to medial wall:
 Ethmoidal air sinuses
 Middle meatus of nose
 Sphenoidal sinus
 Orbital surface:
 Superior oblique muscle in upper part near roof
 Medial rectus muscle in middle part
 In between these two muscles lie anterior ethmoidal nerve,
infratrochlear nerve and terminal branch of ophthalmic artery
29

30.  Lacrimal fossa
 Bounded anteriorly by anterior lacrimal crest
 Posteriorly by posterior lacrimal crest
 Content: lacrimal sac along with its fascia
 Lacrimal crest
 Posterior to lacrimal crest there is attachment of Horner’s muscle ,
septum orbitale and check ligament of medial rectus
30

31.  Infection of ethmoidal sinuses can easily extend into orbit
 Frequently eroded by chronic inflammatory lesions, cysts and
neoplasm that originate in adjacent air sinuses
 Easily fractured during injuries as well as during orbitotomy
operations
 During surgery hemorrhage is common due to injury to
ethmoidal vessels
31

32.  Anterior open end bounded by orbital margins
 Four parts:
 Superior orbital margin
 Lateral orbital margin
 Medial orbital margin
 Inferior orbital margin
32

33.  Formed entirely by orbital arch of frontal bone
 Lateral 2/3rd is sharp and medial 1/3rd is rounded
 About 10mm medial to supraorbital notch is supratrochlear
groove
33

34.  Strongest and formed by zygomatic process of frontal bone and
zygomatic bone
 It doesn’t reach as far anterior as medial margin
34

35.  Formed by zygomatic bone laterally and maxilla medially almost
equal proportion
 Medially, it becomes continuous with anterior lacrimal crest
 Infraorbital foramen is situated 4-5 mm below orbital margin in
line with supraorbital foramen
35

36.  Formed below by anterior lacrimal crest on frontal process of
maxilla and above by frontal bone
 Its upper part becomes continuous with posterior lacrimal crest
36

37.  Superior aperture
 Superomedial aperture
 Inferomedial aperture
 Inferior aperture
 Inferolateral aperture
37

38.  Superior aperture is comma shaped orifice lies between roof of orbit
and upper surface of LPS
 Superomedial aperture is vertically oval lies between reflected tendon
of superior oblique and medial check ligament , infratrochlear nerve
dorsal nasal artery and angular vein pass through this aperture
 Inferomedial aperture is vertical oval and lies between medial check
ligament origin of IO and lacrimal sac
 Inferior aperture is triangular in shape and is bounded by IO and floor
of orbit
 Inferolateral aperture is small oval situated between arcuate
expansion of IO land lateral check ligament
38

39.  Posterior end of orbit where four orbital wall converge
 Has two orifices:
 Optic canal
 Superior orbital fissure
39

40.  Connects orbit to middle cranial fossa ,transmits optic nerve
and ophthalmic artery
 Located with in lesser wing of sphenoid
 Measurements:
 Average length – 6-11mm
 Orbital end is vertically oval6-6.5mm vertically and 4.5-5mm
horizontally
 Middle portion is circular5*5mm
 Cranial end is horizontally oval4-6mm vertically and 5-7mm
horizontally
40

41.  Blunt trauma cause optic canal fracture shearing nerve
resulting in traumatic optic neuropathy
 Enlarged in:
 Optic glioma
 Optic nerve sheath meningioma
 Metastasis
 Neurofibromatosis
 Narrowing in fibrous dysplasia
41

42.  Comma shaped fissure lies between roof and lateral wall
separating lesser and greater wing of sphenoid
 Divided into upper, middle and lower parts by common
tendinous ring
42

43.  Tolosa Hunt Syndrome
 Inflammation of SOF and apex may result in a multitude of signs
including ophthalmoplegia and venous outflow obstruction
 Superior Orbital Syndrome
 Fracture at superior orbital fissure  involvement of cranial nerves
 Diplopia, Ophthalmoplegia, Exophthalmos, Ptosis
43

44.  Lies just below SOF , between lateral wall and floor of orbit
 Bony defect that joins orbit to pterygopalatine and infratemporal
fossa
 Transmits:
 Infraorbital and zygomatic branches of maxillary
division of fifth cranial nerve
 Orbital branch of pterygopalatine ganglion
 Branch of inferior ophthalmic vein which
communicates with pterygoid plexus
44

45.  Eyeball
 Periorbita
 Orbital fascia
 Orbital fat
 Extraocular muscle
 Lacrimal gland
 Orbital nerves and vessels
45

46.  Periosteum lining orbital surface of bones of orbit
 Loosely adherent to bone except at:
 Orbital margin
 Superior and inferior orbital fissures
 Optic canal
 Lacrimal fossa
 At sutures
46

47.  Provides resistance to spread of infections and tumors from
sinuses and bones into orbit
 As loosely adherent to bones, pus or blood may easily collect
beneath it
47

48.  Connective tissue septa suspended from periorbita to form a
complex radial and circumferential interconnecting slings
 Surrounds extraocular muscles, optic nerve, neuro-vascular
elements and fat lobules
48

49.  Preseptal cellulitis: inflammation of structure anterior to orbital
septum that is largely the lids
 Orbital cellulitis: purulent inflammation of cellular tissue behind
orbital septum
49
Preseptal cellutitis

50.  Thin connective tissue lining intraorbital structures
 Can be described as:
 Fascia bulbi or Tenon’s capsule
 Muscular sheaths
 Intermuscular septa
 Membranous expansions of extraocular muscles
 Ligament of Lockwood
50

51.  Fibrovascular tissue envelops globe from limbus to optic disc
 Inner surface is well defined and lies in close contact with sclera
 Outer surface lies in contact with orbital fat posteriorly and with
subconjunctival tissue anteriorly
 Separated from sclera by episcleral space (Tenon’s space)
 Pierced posteriorly by optic nerve, ciliary nerves and vessels
51

52.  Parts of orbital fascia covering muscles like gloves
 Becomes continuous with perimysium
52

53.  Joins sheaths of 4 recti muscles
 Divides orbital cavity and orbital fat into a central and a
peripheral part
53

54.  Lateral and Medial check ligaments
 Expansion of superior rectus muscle
 Expansion from inferior rectus muscle
 Expansion from inferior oblique
 Suspensory ligament of Lockwood
 Superior transverse ligament of Whitnall
54

55.  Medial check ligaments : fascial expansions of lateral and medial
rectus dmuscles and are strong and attached to orbital tubercle on
zygomatic bone and to lacrimal bone respectively
 Expansion of superior rectus muscle attached to levator palpebrae
superioris, when superior rectus makes eye look up the upper lid is
also raised
 Expansion from inferior rectus muscle is attached to
capsulopalbebral fascia
 Expansion from inferior oblique passes to lateral part of roof of orbit
 Suspensory ligament of lodkwood :fascial sheath extending from
posterior lacrimal crest to lateral orbital tubercle formed by
expansions from muscular sheath of MR IO IR
 Superior transverse ligament of Whitnall is thickened band of
orbital fascia which extends from trochlear pulley to lacrimal gland
and its fossa it forms true check ligament of levator muscle
55

56.  Fills space surrounding globe, extraocular muscles, nerves and
blood vessels
 Supports intraorbital structures
 Can be divided into:
 Central intraconal
 Peripheral extraconal
 Anterior peribulbar
56

57.  Traction on fat pad during surgery may cause deep orbital
hemorrhage and compartment syndrome
 Herniation of orbital fat in eyelids can occur due to weakening of
orbital septum because of aging
57

58.  Occurs primarily via ophthalmic artery, a branch of internal
carotid artery
 Small contribution via internal maxillary and facial artery,
branch of external carotid artery
58

59.  Superior ophthalmic vein receives blood from:
 Supraorbital and supratrochlear veins
 Superior and inferior medial palpebral veins
 Medial ophthalmic vein
 Superior vortex vein
 Central retinal vein
 Lacrimal vein
 Some muscular veins
59

60.  Inferior ophthalmic vein receives blood from:
 Lower eyelid and lacrimal sac
 Medial and inferior rectus muscles
 Inferior oblique muscle
 Inferior vortex veins
60

61.  Sensory by ophthalmic and maxillary division of trigeminal
nerve
 Motor by cranial nerve III, IV, VI and VII
 Sympathetic innervation by plexus around internal carotid
artery
 Parasympathetic innervation by ciliary ganglion
61

62. 62

63.  Between orbital bones and periorbita
 Tumours commonly seen in this space:
 Dermoid cyst
 Epidermoid cyst
 Mucocele
 Subperiosteal abscess
 Myeloma
 Hematoma
 Fibrous dysplasia
63

64.  Between periorbita and extraocular muscle
 Tumors present in this space produce
eccentric proptosis
 Common tumors found in this space:
 Malignant lymphoma
 Capillary hemangioma of childhood
 Intrinsic neoplasms of lacrimal gland
 Pseudotumor
64

65.  Called muscular cone or posterior or retrobulbar space
 Bounded anteriorly by Tenon’s capsule lining back of eye and
peripherally by extraocular rectus muscles and their
intermuscular septa
 Tumors common in this space:
 Cavernous hemangioma of adults
 Solitary neurofibroma
 Neurilemomas
 Nodular orbital meningiomas
 Optic nerve gliomas 65

66.  Space between Tenon’s capsule and sclera
 Pus collected in this space is drained by incision of Tenon’s
capsule through conjunctiva
 Steroid injection are injected in this space for posterior segment
disease
66

67.  Space between optic nerve and nerve sheath
 Continues with intracranial space
 If ICP raises then it is transmitted through this space to optic
nerve head leading to papilledema
67

68.  Infantile orbits are more divergent than those of adults
 Orbital axis:
 Lies in horizontal plane in infants
 Slope downwards in adults
 Orbital fissures are relatively larger in childhood than in adults
68

69.  Orbital index- higher in children than in adults
 Interorbital distance is smaller in children
 Roof much larger than floor in infancy
 Optic canal has no length at birth
 Periorbita much thicker and stronger at birth than in adults
69

70.  Holes, particularly in roof due to absorption of bony wall
 Orbital fissures become wider
70

71.  In males: Glabella and superciliary ridges are more marked
 In females: orbit is more elongated and relatively larger than
males. Frontal eminences are more marked
71

72.  Richard S. Snell, Michael A. Lemp, Clinical Anatomy of Eye, 2nd
Edition
 Fundamental and Principles of Ophthalmology, AAO, 2019-2020
 Wolff’s Anatomy of Eye and Orbit, 8th Edition
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73. 73