anatomy of orbit

1. ANATOMY OF
HUMAN ORBIT
Dr. Rakshya Basnet
1st year resident
NAMS,LEI

2. Topics
Development of orbit
Bony orbit:
orbital dimensions
orbital margin
orbital walls
Orbital fissures and canals
Orbital contents
Surgical spaces

3. ORBIT
 pear shaped bony cavity
containing globes, extra ocular
muscles, nerves, fat & blood vessels
 Above- anterior cranial fossa
 Below- maxillary sinus
 Lateral-temporal and middle cranial
fossa
 Medial-nasal cavity &ethmoid air cells

4. Development of orbit
Begins at 6 wk of gestation
Mesenchyme derived from the cranial neural crest
surrounding optic vesicle
 except endothelium of orbital vessels & extraocular
muscles – true mesoderm)

5.  Neural crest cells migrate ventrally over face in two waves:
- Maxillary wave: floor and lateral wall of the orbit
- Frontonasal wave: lacrimal and ethmoidal bones

6. Clinical significance
 Deficits in neural crest cell migration and
differentiation cause CRANIOFACIAL abnormalities
 Failure of fusion of neural crest waves results in
clefting syndromes such as dermoid cyst
( at the frontozygomatic and frontoethmoidal suture
lines )

7. Orbital bones ossify & fuse (6th -7th months of
gestation)
- Orbital bones undergo Membranous ossification
except lesser wing of sphenoid
Growth of orbit corresponds with growth of eyeball

8. eyeball reaches adult size by 3 years
but orbit & mid-face till age of 16 years.
orbit will fail to reach its normal volume if globe
micro-ophthalmic, enucleated or radiotherapy in
high doses

9. As the orbital bones develop, the eyes converge from an initial 180°
relation to their final position of 68°
Fig: Angular separation of globes at diff. ages

10. Bony Anatomy
pyramidal shaped
- Base: quadrangular anterior
opening, 4 cm x 3.5 cm
- Apex: formed by the optic canal
and the superior orbital fissure.
- Walls: 4 (medial, lateral, roof &
floor)

11. CONTD.
 medial orbital walls are
approximately parallel
 lateral wall lies at the angle of
45 degree to the medial wall
 lateral walls of the 2 orbits
are at 90 degree to each
other

12. Measurements
Criteria Value
Volume ≈30ml
Height 35mm
Width 40mm
Depth 42-50mm
Interorbital
distance
25mm

13. ORBITAL INDEX
ORBITAL INDEX TERMED AS RACE
>89 Megasemes Orientals
(mongoloid)
83-89 Mesosemes Caucasians
(European and
English)
<89 Microsemes negroid
Orbital index= (Height/WidthX 100

14. Orbital rim/BASE of orbit
roughly spiral in shape : i.e Superior margin is continuous with
the posterior lacrimal crest and inferior margin continuous with
anterior lacrimal crest.

15. Orbital rim
1. Superior orbital rim:
- formed by orbital arch of frontal bone
1. Supraorbital notch :
 at summit of arch
 at junction of lateral 2/3rd and medial 1/3rd
 transmits supraorbital nerve and vessels
2.Supratrochlear groove:
 is present 1 cm medial
 to supraorbital notch
 transmits supratrochlear nerve and artery

16. Orbital rim
2.Lateral orbital rim:
 strongest part of orbital outlet
 formed by zygomatic process
of frontal and zygomatic bone
-

17. Orbital rim
3.Inferior orbital rim:
- Formed by zygomatic and maxillary bone
equally.
-medially continuous with anterior lacrimal
crest
- Infra orbital foramen is present 4 – 5 mm
below the margin in line with supraorbital
foramen

18. Orbital rim
4.Medial orbital rim:
- Formed above by frontal
bone
- Below by anterior lacrimal
crest on the frontal process of
maxilla & posterior lacrimal crest
on lacrimal bone.

19. Each orbit is formed by seven bones

20. WALLS OF THE ORBIT

21. Roof or VAULT
Formed by -:
The Frontal Bone
The Lesser wing of the Sphenoid

22. LANDMARKS
Lacrimal fossa
Fovea for trochlea of
SO
Frontosphenoidal
suture

23. Landmarks
FOSSA FOR THE LACRIMAL GLAND
 It is located behind the zygomatic process of the frontal bone
 Contains:
 lacrimal gland
 some orbital fat
(accessory fossa
of Rochon-Duvigneaud)

24. TROCHLEAR FOSSA (FOVEA)
-small depression close to frontolacrimal suture;
about 4 mm from orbital margin
-insertion of tendinous pulley of Superior Oblique
-sometimes (≈10%) surmounted by a spicule of
bone (Spina trochlearis)

25. Frontosphenoidal suture
•between frontal and the lesser wing of the
sphenoid
•usually obliterated in the adults

26. Cribra orbitalia
 apertures apparent on the medial side of
anterior portion of the lacrimal fossa
 It imparts porous appearences to the bone and
allows veins to pass from diploë to the orbit
 Best marked in the fetus and infant

27. Applied Anatomy:Roof
 Mucocele from the frontal sinus extends to orbital cavity
 Fracture of superior margin may damage or displace trochlea and
producing symptoms of superior oblique palsy
 thin and fragile except lesser wing so penetrating wound over upper lid
may cause its fracture and injury to frontal lobe
 In old age,roof absorbed at places, so that periorbita and duramater
come into contact- Increased risk of postoperative CSF leaks.
 It can easily nibbed away in transfrontal orbitotomy

28. The Lateral Wall
Thickest wall
LPS
LPL
LCL

29. RELATIONS
 Laterally, lateral wall separates orbit from temporal fossa anteriorly& from middle
cranial fossa posteriorly
 Medially,related to LR muscle, lacrimal nerve and vessels, zygomatic nerve
&communications between zygomatic & lacrimal nerves
 Posteriorly, there is a small bony projection called spina recti lateralis which gives
origin to part of LR muscle
 Anteriorly, wall is marked by zygomatic groove & foramina which are traversed
by zygomatic nerve and vessels

30. LATERAL WALL OF ORBIT
1. sphenoidal area is separated from roof
and floor by superior and inferior orbital
fissures
2. zygomatic area merges with floor ,
joins roof at frontozygomatic suture

31. Contains lateral orbital tubercle of
Whitnall which gives attachment to:
 Whitnall’s ligament
 check ligament of lateral rectus
 Lockwood ligament
 Lateral horn of levator aponeurosis
 lateral canthal tendon
 ORBITAL SEPTUM

32. Applied Anatomy
 In resection of maxilla, the Whitnall’s tubercle is spared, otherwise
Damage to Lockwood’s ligament
Inferior dystopia of eye ball
Diplopia

33. CLINICAL APPLICATIONS
 Thickest and strongest wall
 protects only posterior half of eyeball hence palpation of retrobulbar
tumors is easier from lateral side
 devoid of foramina so there is decreased chance of hemorrhage in
surgery
 zygomatico-sphenoidal suture is an important landmark in creating
flap in kronlein’s operation
Once this flap is turned there is direct access to superolateral,
inferolateral &retrobulbar quadrants of orbit

34. Medial wall
 thinnest ,quadrilateral
(0.2 mm to 0.4 mm)
 Formed, from anterior to
posterior, by 4 bones:
1. frontal process of maxilla
2. lacrimal bone
3. orbital plate of ethmoid
4. small part by body of
sphenoid

35. RELATIONS
 Medial to medial wall
- anterior, middle and posterior
ethmoidal sinus
- sphenoidal sinus
- middle meatus of nose
 The orbital surface of medial wall is
related to
- superior oblique muscle-upper part
near roof
- medial rectus muscle –in middle part

36. Landmarks
 LACRIMAL FOSSA:
- Anterior part bears lacrimal sac fossa
which is continous inferiorly with
nasolacrimal canal
- Formed by:
- frontal process of maxilla
- lacrimal bone
- Boundaries:
- Anterior- anterior lacrimal crest
- Posterior- posterior lacrimal crest

37. Lacrimal Fossa
- Dimensions-
- Length≈ 14 mm
- Depth≈ 5 mm
- Continuous below with bony nasolacrimal canal
- Content-
 Lacrimal sac along with its fascia

38. IMPORTANT LANDMARKS
-just behind the posterior lacrimal crest
1. Horner’s muscle
2. septum orbitale
3. check ligaments of the medial rectus

39. FRONTO ETHMOIDAL SUTURE LINE
-Marks approximate level of ethmoidal
sinus roof
-Breach of this suture may open the frontal
sinus, or cranial cavity
-Anterior and posterior ethmoidal foramina
are present in suture line

40. Anterior ethmoidal foramen
-20-25 mm posterior from anterior
lacrimal crest
-Opens in anterior cranial fossa at side
of cribriform plate of ethmoid
-Transmits-
- anterior ethmoidal nerve & vessels

41. Posterior ethmoidal foramen
-32-35 mm posterior from anterior
lacrimal crest
-7 mm anterior to anterior rim of optic
canal
-Transmits
Posterior ethmoidal nerve & vessels

42. Weber suture
Lies anterior to lacrimal fossa/
Sutura longitudinalis
imperfecta/sutura notha
Runs parallel to anterior lacrimal crest
Branches of infraorbital artery pass through
this groove to supply nasal mucosa
Bleeding may occur from these vessels
during DCR surgeries

43.  Anteriorly located suture indicates predominance of lacrimal
bone
 Posteriorly located suture indicates predominance of
maxillary bone*
*If maxillary component is predominant, it becomes difficult to
perform osteotomy to reach sac during DCR, because
maxillary bone is very thick.

44.  Medial wall extremely fragile (presence of ethmoidal air cells and
nasal cavity)
 Accidental lateral displacement of medial wall- traumatic
hypertelorism
 Medial wall provides alternate access route to the orbit through the
sinus

45. Ethmoid
- Thinnest bone of the orbit
- Inflammation in the ethmoid sinus spreads readily
to the orbit

46.  Tumours,cyst,inflammation of nasal cavity can breach lamina
papyracea to involve the orbit
 Lacrimal bone can be easily penetrated during endoscopic DCR
 During surgery, hemorrhage is most troublesome due to injury to
ethmoidal vessels.

47. Floor of the orbit
 Shortest orbital wall, triangular and
0.5 – 1 mm thick.
 Slopes 20° downward from posterior
to anterior
 Formed by:
- orbital plate of maxilla
- orbital surface of zygomatic bone
- orbital process of palatine bone

48. RELATIONS
below: maxillary air sinus
palatine air cells
above: inferior rectus muscle
inferior oblique muscle
nerve to inferior oblique

49. Landmarks
infraorbital foramen
•Posterior part of floor is separated from
lateral wall by IOF.
•which is continuous anteriorly with
infraorbital groove
• which extends anteriorly as canal.
•canal opens as infraorbital foramen
4mm below orbital margin
transmit infraorbital nerve, vessels and V2

50. Applied Anatomy
Orbital blow out fracture refers to fracture of orbital floor
fracture usually results when an object larger than the
transverse diameter of orbit strikes the globe.

51. 
 sudden increase in intraorbital pressure causes break in orbital floor
resulting in enophthalmos secondary to herniation of ocular content into
maxillary sinus.
 Fracture may injure infraorbital nerve, resulting hypoesthesia of skin of cheek
and upper teeth on side of injury.
 Tumors of maxillary sinus extend superiorly into orbital cavity and cause
non-axial proptosis.
 Can be approached by inferior orbitotomy easily

52. Orbital Openings

53. APEX of orbit
 Posterior end of orbit
 4 walls converge
 2 orifices:
 Below OC, IOF joins SOF & continuous with foramen
rotundum

54. Optic canal
 Connects orbit to middle cranial fossa
 located in the orbital roof at the apex
 Located within lesser wing of sphenoid
 Separated from SOF by optic strut
- Measurement:
Orbital end: 5–6 mm horizontally and 6-8 mm vertically
Cranial end: 5–7 mm horizontally and 4–6 mm vertically

55. Structures passing through it:
-Optic nerve and its meninges
-
- Ophthalmic artery &
Sympathetic nerves
- Blunt trauma cause optic canal fracture shearing nerve
causing traumatic optic neuropathy.
Clinical significance:

56.  The optic canal attains adult dimensions by age 3 year and
is symmetric.
 1 mm difference of canal diameters is significant.
 Enlarged in
optic glioma
optic nerve sheath meningioma
metastasis
Neurofibromatosis
Narrowing in fibrous dysplasia

57. Superior orbital fissure
 Comma shaped fissure, wider inferiorly
measuring 20-25 mm in length
 Located between the greater & lesser
wing of sphenoid.
 largest communication between orbit
and middle cranial cavity

58. Superior orbital fissure
 Lies between lesser & greater wings of sphenoid bone,
between the upper and lateral walls of orbit

59. Clinical applications
 Radiographic enlargement of the superior
orbital fissure may occur in:
- meningioma
- pituitary adenoma or
- tumors of the orbital apex

60. Inferior orbital fissure
 Lies between lateral wall and floor
of the orbit
 30 mm bony defect that joins orbit
to pterygopalatine and
infratemporal fossa

61. Structures passing through it:
 Infraorbital nerve
 Zygomatic nerve
 Infraorbital artery
 Infraorbital vein
 branches of inferior ophthalmic vein
 Parasympathetics to lacrimal gland
 branch of pterygopalatine ganglion

62. SOF Syndrome/ Rochon-Duvigneaud's
syndrome
 Caused by Fracture through orbital roof
• varying degree of CN III, IV, V-1 and VI palsy
• CN V-2 and CN II spared
• diplopia, paralysis of extra ocular muscle, proptosis

63. Orbital apex syndrome
- features of SOF syndrome + CN II involvement
(Tolosa Hunt syndrome)

64. 3.Cavernous sinus syndrome:
- features of SOF syndrome + CN V-2
- combination of sympathetic nerve palsy (Horner’s) + CN III or IV said to be specific

65. Orbital contents
1.eyeball
2.Periorbita
3.Orbital fascia
4.Orbital fat
5.Extraocular muscle
6.Lacrimal gland
7.Orbital vessels
8.Orbital nerves

66. Periorbita
 periosteal covering of orbital
bones
Is loosely adherent to bone,
except at :
- anterior orbital margins
(thickened to form arcus
marginale)
- sutures
- fissure and foramina
- lacrimal fossa

67. Periorbita contd…
 divides at posterior lacrimal crest to enclose
lacrimal sac.
 Quiet sensitive and supplied by frontal, lacrimal,
ethmoidal, zygomatic and infraorbital nerve.

68. Posteriorly, around orbital apex thickens to form a fibrous ring - common
tendinous ring
PERIOSTITIS- Inflammation of band of tissue that surrounds
bone(periosteum)
Periorbita contd…

69. Clinical applications
- Provides resistance to spread of infections and tumors from
the sinuses and bones into orbit
- As loosely adherent to bones, pus or blood may easily
collect beneath it.
- During exenteration, it should be carefully lifted at sites
where it is firmly adherent.
Periorbita contd…

70. Orbital septal system
Includes
 connective
tissue septa which are
suspended from
periorbita to form a
complex radial
and circumferential
interconnecting slings.
 These septa surround Extraocular muscles,
Optic nerve, neuro-vascular elements and the
fat lobules

71. Clinical significance
 PRESEPTAL CELLULITIS- Inflammation of structure anterior to the
orbital septum that is largely the lids.
 ORBITAL CELLULITIS- Purulent inflammation of of the cellular tissue
behind the orbital septum.

72. ORBITAL FASCIA
 Thin connective tissue membrane lining various intraorbital contents.
 4 parts:
1. Fascia bulbi or Tenon’s capsule
2. Fascial sheaths of extraocular muscles
3. Intermuscular membrane
4. Fascial expansions of extra ocular muscles

73. 1. Fascia bulbi or tenon’s capsule:
fibrovascular tissue envelops globe from
limbus to optic disc
Inner surface: episcleral space
Outer surface: subconjunctival tissue
(anteriorly ) & orbital fat ( post. )
ORBITAL FASCIA contd..

74. Clinical significance
 TENONITIS Tenon's capsule may be affected by a disease called
idiopathic orbital inflammation,
Local anaesthesia :
may be instilled into space between Tenon's capsule and sclera to
provide anaesthesia for eye surgery, principally cataract surgery

75. ORBITAL FASCIA contd..
2. Fascial sheaths of extraocular
muscles :
- parts of orbital fascia covering muscles
like gloves.
- become continuous with perimysium
3. Intermuscular septa/membrane:
- join sheaths of 4 recti
muscles
- divide orbital cavity & orbital fat into
central and peripheral parts.

76. ORBITAL FASCIA cont..
4. Fascial expansions of extraocular
muscles:
- Suspensory ligament of Lockwood
- Medial and lateral check ligaments
- Suspensory ligament of fornices
- Superior transverse ligament of Whitnall

77. Orbital fat
 Fills the space surrounding the
globe, extraocular muscles, nerves
& blood vessels
 supports intraorbital structures but
does not provide energy reserve
 Can be divided into:
- central intraconal
- peripheral extraconal
- anterior peribulbar

78. Significance:
 traction on fat pad during surgery may cause deep
orbital hemorrhage & compartment syndrome
 Herniation of the orbital fat in eyelids (Steatoblepharon)
can occur due to weakening of orbital septum because
of aging.
Fig: Steatoblepharon with appearance of "bags under eyes.

79. Arterial Supply
 Occurs primarily via ophthalmic artery, a branch of internal
carotid artery.
 external carotid artery gives small contributions via internal
maxillary and facial artery
Internal carotid
External carotid

80. 1. Ocular (Posterior):
- Central retinal artery
- Short posterior ciliaries (15–20)
- Long posterior ciliaries (2)
2. Orbital (Middle):
- Muscular or anterior ciliaries (7)
- Lacrimal
Branches of Ophthalmic artery
subdivided into 3 goups:

81. 3. Extraorbital (Anterior)
- Anterior & posterior ethmoidals
- Supraorbital
- Terminal branches (supratrochlear, infratrochlear, and dorsal
nasal)
Branches of Ophthalmic artery
subdivided into 3 goups:

82. VENOUS DRAINAGE
Superior ophthalmic vein:
 major venous drainage of orbit
 receives blood from:
- Supraorbital & supratrochlear veins
- Superior and inferior medial
palpebral veins
- Medial ophthalmic vein
- Superior vortex vein
- Anterior ethmoidal vein
- Central retinal vein
- Lacrimal vein
- some muscular veins
- sometimes the inferior ophthalmic vein

83. VENOUS DRAINAGE
Inferior ophthalmic vein:
Receives blood from:
- Lower eyelid and lacrimal
sac
- Medial and inferior rectus
muscles
- Inferior oblique muscle
- Inferior vortex veins

84. Nerve supply of the orbit
Sensory supply by opthamic and maxillary
division of trigeminal nerve
 Motor innervation by cranial nerve III, IV, VI & VII
Sympathatic innervation by plexus around
Internal carotid artery
Parasympathetic innervation by cilliary ganglion

87. Spaces in relation to orbit
1. subperiosteal
2. Peripheral/extraconal
3. Central/intraconal
4. Sub tenon’s
5. subarachnoid

88. 1.Subperiosteal Space
Between bones of orbital wall &
periorbita.
periosteum is detachable in most
parts except at its attachment at
margin, roof & fissures.

89. 2.Extraconal space
 Between periorbita & EOM
 Collection of fluid in space may exude through
orbital septum & lead to edema of eyelid.
 Tumor in this space can lead to nonaxial
proptosis

90. 3.Intraconal space
 A cone shaped area enclosed by 4 rectus muscles &
their fascial expansions.
 Contains optic N and its meningeal coverings,
superior and inferior divisions of III N,VI N
ophthalmic A, superior ophthalmic V & nasociliaryN
 presence of any tumor or fluid in this space usually
results in Axial proptosis.

91. 4.Subtenon space
 Space that lie between Tenon’s capsule
and the globe
 Pus collection in this space need to be
drained by incision of tenons capsule through
conjunctiva.
 Steroid injection are injected in this space
for posterior segment disease

92. Subarachnoid Space
Space between optic nerve and nerve
sheath
Continues with intracranial space
If ICP raises then transmited through
this space to optic nerve head leading to
papilloedema
If retrobulbar anaesthetic injection is
accidentally given into this space can
lead to respiratory arrest

93. Congenital anomalies of orbit
Anophthalmia
 True Anophthalmia is defiend by Duke-Elder as total absence
of tissues of eye.

94. Craniosynostosis
 Premature closure of 1 or more sutures
in bones of skull, results in various skeletal
deformities
 Hypertelorism and proptosis are
frequently observed in craniosynostosis
syndromes
 Crouzon and Apert syndromes

96. Hypertelorism
 Is a symptom.
 In this condition the ICD, IPD and OCD is increased.
Hypertelorism should not be confused with
Telecanthus, in which the ICD is increased but IPD and
OCD is normal

97. References
 Duane’s clinical ophthalmology(2010)
 Diseases of the Orbit: A Multidisciplinary Approach, Jack Rootman, 2nd
edition
 Atlas of Clinical and Surgical Orbital Anatomy: Jonathan J. Dutton, 2nd
edition
 Wolff’s anatomy of the eye and orbit(8th edition)
 AAO 2011-2012 BCSC series (section7 and section 2
(Fundamental..& orbit, eyelids and lacrimal system)