Dr, Kathirvel Gopalakrishnan M.D.S (OMFS) Presentation on Anatomy of orbit which helps for a quick refresh. Applied aspects described well and slides contains images for easy understanding of the subject.

1. ANATOMY OF ORBIT
Dr. Kathirvel G
PG OMFS

2. Contents:
• Embryology
• Osseous anatomy
• Orbital Contents
• Muscles
• Arterial and venous supply
• Nerve supply
• Surgical approach

3. Within 2 month of embryogenesis :
Scaffolding of the orbital bones
Migration of neural crest cells follows 2 routes
• Frontonasal anlage migrates over the prosencephalon from above
• Frontonasal process develops Floor and lateral wall of orbit
• Maxillary wave curves around the developing eye from below
• Maxillary process develops Lacrimal and ethmoid bones

4. 6th – 7th month of gestation :
Orbital bones ossify and fuse together
• Orbital bones including the greater wing of the sphenoid arise from
membranous connective tissue
• Lesser wing of the sphenoid arises from a cartilaginous substance

5. • The eyes gradually converge from an
initial 180 relation to each other at 2
months gestation to a 71 relation at birth
• Postnatal changes in skull growth
contribute to the final position of the
orbits.

6. OSSEOUS ANATOMY

7. • The orbit is a bony pyramid with four walls: a roof, lateral
wall, floor and medial wall.
• The base of the pyramid is the orbital entrance, which is
roughly rectangular
• It measures 4 cm wide by 3.5 cm high
• The apex of the orbital pyramid is situated 44–50 mm
posteriorly
• The orbital volume is roughly 30 ml of which 7 ml is
occupied by the globe

8. Composed of 7 bones
•Sphenoid
•Frontal
•Zygomatic
•Ethmoid
•Lacrimal
•Maxilla
•Palatine

9. THE MEDIAL WALL:
• Very thin, roughly rectangular
• Extends from the frontal process of the
maxilla to the orbital apex.
• Formed by
The body of the sphenoid
The orbital plate of ethmoid bone
The lacrimal bone
The frontal process of the maxilla

10. Contents:
• Lacrimal groove lies anteriorly to the medial wall, bounded anteriorly by lacrimal
crest of frontal process of maxilla and posteriorly by lacrimal crest of lacrimal bone
• It lodges lacrimal sac
• Leads inferiorly, through the nasolacrimal duct to the inferior meatus of the nose
• The vast majority of the medial wall is comprised of the lamina papyracea

11. Contents:
• Anterior and Posterior ethmoidal foramina
• The anterior and posterior ethmoidal nerves and
vessels leave the orbit via their respective
foramina located in the frontoethmoid suture
Relations:
• Orbital plate of ethmoid separates orbit from
ethmoidal air sinuses
• The medial wall articulates with the roof at the
fronto-ethmoid suture
• The medial wall articulates with the floor at the
maxillo-ethmoid suture

12. Applied anatomy:
• The lamina papyracea fractures readily follow blunt orbital trauma
• Paper thin lamina papyravea overlying the ethmoid sinus facilitates the spread of
infection, in cases of ethmoid sinusitis, into the orbit with subperiosteal abscess
formation and/or orbital cellulitis
• Hemorrhage may occur due to damage to ethmoidal vessels
• Medial wall may be displaced laterally due to trauma – traumatic hypertelorism

14. THE LATERAL WALL:
• Thickest and strongest of all
walls of orbit
• Formed by
Greater wing of the
sphenoid posteriorly
Orbital surface of frontal
process of zygomatic bones
anteriorly

15. Contents:
• Superior orbital fissure posteriorly, at the junction between roof and lateral wall
• Foramen for zygomatic nerve seen in zygomatic bone

16. Symptoms:
• Impairment of oculomotor, trochlear and
abducent nerves causing ophthalmoplegia
• Ptosis due to loss of function of levator
palpebrae superioris
• Fixed dilated pupil with loss of accommodation
• Proptosis due to decreased tension of extra
ocular muscle
• Anesthesia of fore head and upper eyelid due to
compression of lacrimal and frontal nerves of
ophthalmic branch of trigeminal nerve

17. Contents:
Whitnall’s tubercle :
• Palpable elevation on zygomatic bone just within the orbital margin.
• 4-5 mm behind lateral orbital rim
• 11 mm inferior to fronto-zygomatic suture line
Attachments:
• Levator superioris aponeurosis
• Lateral rectus check ligament
• Lockwoods ligament
• Lateral canthal tendon
• Lacrimal gland fascia

18. Relations:
• Separated from the floor by the inferior orbital fissure and from the roof by the
superior orbital fissure (posteriorly)
• The zygomaticofacial and zygomaticotemporal neurovascular structures leave the
orbit via their respective foramina on the lateral wall

19. Applied anatomy:
• Damage to whitnalls tubercle causes diplopia
• Devoid of foramen, so less hemorrhage
• Protects posterior half of the globe
• During lateral orbitotomy surgery, the superior bone cut is usually made just
above the frontozygomatic suture

20. THE FLOOR:
• Slopes upwards and medially to join
the medial wall
• The floor separates the orbital cavity
from the maxillary sinus.
• Composed of
The lower part of orbital surface
of zygomatic bone anteriorly
The orbital process of the
palatine bone and
The orbital process of the
maxillary bone.

21. Contents:
• Inferior orbital fissure occupies in posterior part of the junction between lateral
wall and floor
• The zygomatic branch of maxillary division of the trigeminal nerve (V2),
infraorbital branch of the maxillary artery, the inferior ophthalmic vein passes
through inferior orbital fissure
• Through this fissure, the orbit communicates with the infratemporal fossa
anteriorly and pterygopalatine fossa posteriorly
• Infraorbital groove runs forwards in relation to the floor

22. Relations:
• The orbital floor is the roof of the maxillary sinus and separated orbital cavity
from maxillary sinus
Applied anatomy:
• Commonly involved in blow out fractures of orbit
• Easily invaded by tumors of maxilla

23. THE ROOF:
• The roof is thin and concave in a
downward direction.
• Formed by
Orbital plate of frontal bones
Posteriorly by lesser wing of
sphenoid

24. Contents:
• The lacrimal fossa in the anterolateral part, which lodges lacrimal gland
• Optic canal lies posteriorly, at junction of roof and medial wall
• Trochlear fossa, lies anteromedially, provides attachment for tendon of superior
oblique muscle
• At the junction of the medial third and lateral two-thirds of the superior orbital
rim transmits the supraorbital neurovascular bundle

25. Relation:
• Has a ridged, convex upper surface which forms the floor of the anterior cranial
fossa
• There is variable pneumatization of the roof by the frontal sinus
Applied anatomy:
• At the junction of roof and medial wall, the suture line lies in proximity to the
cribriform plate of ethmoid. During trauma, rupture of dura mater and CSF escaped
into orbit/ nose or both

28. The Orbital Fascia or Periorbita
• This corresponds to the orbital periosteum.
• Its bone attachment is very loose apart from at
points around the optic canal and the superior
orbital fissure where it is continuous with the dura
mater.
• In front, it continues into the cranial periosteum on
the orbital rim to which it is very strongly
attached.

29. • Inside, it is attached to the posterior
lacrimal crest and on top, it is
traversed by the levator palpebrae
superior muscle.
• The periorbita thus surrounds the
contents of the orbit, forms a bridge
over the top, and closes the inferior
orbital fissure. It is perforated by the
various vessels and nerves of the orbit.

30. ORBITAL CONTENTS

31. The orbit can be split into two parts
1. Anterior part - the eyeball
2. Posterior part - the muscles, the vessels and the nerves supplying the eyeball, the so-
called adipose body of the orbit.
• The eyeball does not touch any of the walls but is suspended at a distance of 6 mm
outside and 11 mm inside.

32. • From the optic nerve as far as the sclero-corneal junction, the eyeball is covered by
a two-layer fascia (Tenon’s capsule) with parietal and visceral sheets separating it
from the orbital fatty tissue.

33. ORBITAL MUSCLES

34. ORBITAL MUSCLES
The orbit contains several muscles
1. Levator palpebrae superior muscle
2. Superior tarsal muscle
3. The other six controlling the eye movements
• Four rectus muscles (superior, inferior, lateral and medial)
• Two oblique muscles (superior and inferior)

35. LEVATOR PALPEBRAE SUPERIOR
• Triangular muscle
Origin:
Above and in front of the optic
canal
• It runs along the upper wall of the orbit
just above the superior rectus muscle
(covering its medial edge).

36. Insertion:
• It terminates in an anterior tendon
that spreads out in the form of a large
fascia, which extends out to the
eyelid.
• The edges of this fascia traverses the
lacrimal gland and goes on to attach
to the fronto-zygomatic suture.
Functions:
Elevation on upper eyelid

37. SUPERIOR TARSAL MUSCLE:
• Also known as Muller’s muscle
• The structure is unique in that it adjoins
and originates from underneath another
muscle, the levator palpebrae superioris
• It consists of thin fibers of the smooth
muscle

38. • About 15 mm wide by 10 mm long.
Origin: Underneath the levator palpebrae superioris
muscle
Insertion: Point on the superior tarsal plate of the
upper eyelid.
Nerve supply:
Sympathetic nervous system

39. Clinical significance:
• Damage to this muscle will result in ptosis of the affected eye.
• Damage to the sympathetic nervous system will also cause ptosis.
• One condition in which the superior tarsal muscle is hyperactive is exophthalmia, a
condition associated with hyperthyroidism.
Functions:
• Assists the levator palpebrae superioris by maintaining the elevation of the upper eyelid
after the levator palpebrae superioris has raised it.
• To raise the upper eyelids an additional 2 mm after the levator palpebrae superioris

40. RECTUS MUSCLES:
Origin:
• Common annular tendon (Zinn’s tendon)
• Located on the body of sphenoid near the infraoptic tubercle
• It subsequently splits into four lamellae arranged at right angles to one another, from
which the four rectus muscles arise respectively.

41. • The superolateral and inferomedial ligaments are solid but the
other two are perforated
• Superomedial band lets the optic nerve and the ophthalmic
artery pass through
• Inferolateral band which is larger, stretches between the
inferomedial and superolateral bands passing through
• The rectus muscles then continue for four centimeters in
a forward direction
Insertion:
In tendons which are attached to the anterior part of the
sclera near the limbus.

42. • The frequency of congenital extraocular muscle anomalies increases in
craniofacial dysostosis
• Bilateral agenesis of the SR was reported in Apert’s syndrome
• Congenital absence of the IR muscle may mimic IR palsy especially in the
absence of associated craniofacial anomalies

43. THE OBLIQUE MUSCLES:
The superior oblique muscle:
Origin
• As a short tendon attached inside and above the optic
foramen.
Insertion:
• On the superolateral side of the posterior hemisphere
of the eye.
• It runs along the superomedial angle of the orbit and then becomes tendinous
again when it turns back at an acute angle over the trochlea.
• It then becomes once more muscular and turns backwards in a lateral direction,
skirts the upper part of the eyeball passing under the superior rectus muscle to

44. The inferior oblique muscle:
• Shorter than the superior, is located on the anterior
edge of the floor of the orbit
Origin:
• Outside the orbital opening of the lacrimal canal
• It skirts the lower surface of the eyeball, passing
under the inferior rectus muscle
Insertion:
• On the inferior, lateral side of the posterior
hemisphere of the eye

46. ARTERIES OF THE ORBIT

47. • Ophthalmic artery and its branches
• Although is also supplied by the infraorbital artery, a branch of the maxillary artery which
is itself the terminal branch of the external carotid artery.

48. Ophthalmic artery
Origin:
Arises from ICA medially in the anterior clinoid process
Course:
• In the orbital cavity, it is initially lateral to the optic nerve and medial to the ciliary
ganglion.

49. • Next, it crosses the top side of the optic nerve
below the superior rectus muscle, reaching
the medial orbital wall.
• From there it makes its way forward between
the superior oblique and the medial rectus
muscles
• Passes under the trochlea and then climbs
back up again to pass between the orbital rim
and the medial palpebral ligament.

50. Branch Supply
1.Central retinal artery Retina of eye
2.Lacrimal artery Lacrimal gland,
portion of eyelid and
anterior eyeball.
Gives anterior ciliary
branch to eyeball
3.Posterior ciliary
artery
Pierces sclera and
supply structures
inside eye ball
4.Supra orbital artery Supply forehead and
scalp
5.Supra trochlear
artery
Supplies antero medial
part of forehead
(1)
(3)
(3)
(2)
(5)
(4)

51. Branch Supply
6.Post ethmoidal
artery
Nasal cavity,
Ethmoidal cells
7.Anterior
ethmoidal artery
Nasal septum,
lateral wall of nose
end as dorsal nasal
artery
8.Dorsal nasal
artery
Root of nose
9.Muscular artery Ocular muscles
10.Median
palpebral
Medial part of
upper and lower
eyelids
(7)
(8) (10)
(6)
(9)

53. VEINS OF THE ORBIT

54. Veins of orbit:
• Very dense venous network in the orbit, organized around the two ophthalmic veins
that drain into the cavernous sinus.
• These veins are valve-less.

55. Superior ophthalmic vein
• A large-caliber vein present in all subjects,
constitutes the orbit’s main venous axis.
• It is formed by the union behind the trochlea
of two rami, the first from the frontal veins
and the other from the angular vein.
• This vessel then crosses the orbit from the
front towards the back accompanying the
artery and passing under the superior rectus
muscle.
Termination:
Face of the cavernous sinus

56. Inferior ophthalmic vein
• Result of a venous anastomosis in the anterior
inferomedial part of the orbit.
• It receives rami from muscles, the lacrimal sac
and the eyelids.
• It carries on behind, above the inferior rectus
muscle, whence it often rejoins the superior
ophthalmic vein, although in some subjects, it
carries on to the cavernous sinus as a distinct
vessel.
• It communicates with the pterygoid plexus by
small veins crossing the walls of the orbit.

57. NERVES OF THE ORBIT

58. Nerves of the Orbit
The orbit contains a huge number of nervous structures of various types
They include:
• A component of the central nervous system: Optic nerve
• Three motor nerves: Third, fourth and sixth cranial nerves
• A sensory nerve: Ophthalmic nerve, a branch of the fifth cranial nerve

59. The optic nerve (CN II)
It is conventionally divided into three different parts, namely
• Intracranial segment
• Intracanalicular segment
• Intraorbital segment

60. The intracranial segment
10 mm long and passes behind and inside as far as the optic chiasm.
Blood supply : Recurrent branches of the ophthalmic artery.

61. The intracanalicular segment
5 mm long and the nerve is here accompanied underneath and outside by
the ophthalmic artery.
• Just in front of the canal,
the ophthalmic artery and
carry on medially and in a
forward direction above
the optic nerve
• In this canal, the optic
nerve is separated on the
inside from the sphenoidal
sinus and the posterior
ethmoidal cells by a very
thin lamella of bone.

62. The intraorbital segment:
30 mm long and follows a sinuous trajectory, which provides reserve length
so that the eyeball can be moved without damaging the nerve.
Arterial supply: Posterior ciliary arteries and the central artery of the retina
Venous drainage: Central vein of the retina.

63. Relationship:
• The muscles of the orbit - superior oblique muscle, the medial rectus muscle and the
superior rectus muscle
• The ophthalmic artery which crosses over the nerve
• The ciliary ganglion, with its lateral surface at the union of the anterior 2/3 and the
posterior 1/3 and located between it and the lateral rectus muscle.

64. The oculomotor nerve (CN III)
• Before entering the orbit, this nerve splits to form two terminal rami (superior and
inferior)
• The two branches then enter the muscular cone and diverge away from one
another.
• The superior branch, smaller-caliber branch climbs up the lateral side of the optic
nerve and splits to form four or five rami that innervate the superior rectus muscle

65. • The inferior branch is initially located below and outside the optic nerve and then
spreads out over the upper surface of the inferior rectus muscle, splitting to form
three branches.
• The first of these passes below the optic nerve on its way to the medial rectus
muscle
• The second travels outside towards the inferior rectus muscle
• The third (the longest), carries on in front between the inferior rectus muscle and
the lateral rectus muscle on its way to the inferior oblique muscle

66. The oculomotor nerve (CN III)
Supply:
• All the extraocular muscles except the superior oblique muscle and the lateral
rectus muscle

67. The trochlear nerve (CN IV)
• Enters the orbit across superior orbital fissure.
• It passes outside the common tendinous ring
above the orbital muscles and inside the frontal
nerve.
• Inside the orbit, it carries on medially above the
origin of the levator palpebrae superior, to
reach the superior oblique muscle on its orbital
side.
Supply:
Motor supply to superior oblique muscle

68. The abducent nerve (CN VI)
• Starts in the medial part of the superior orbital fissure inside the common tendinous
ring outside the branches of the oculomotor nerve.
• It then spreads out over the lateral rectus muscle and splits to form four or five
branches, which carry on into the muscle.
Supply: Motor supply to lateral rectus muscle

69. The ophthalmic nerve (CN V1)
A superior branch of the trigeminal nerve
It innervates the eyeball, the lacrimal gland, the conjunctiva, part of the mucosa of the nasal
cavity and the skin of the nose, forehead and scalp.
After its passage into the lateral wall of the cavernous sinus before it enters the orbit, it
splits to form three branches, namely (going from the outside to the inside)
1. The lacrimal nerve
2. The frontal nerve
3. The nasociliary nerve

72. The lacrimal nerve
• Enters the orbit via the lateral part of the superior orbital fissure and remains outside
the cone.
• Then, together with the lacrimal artery, it travels along the superolateral edge of the
orbit above the lateral rectus muscle and from the zygomaticotemporal nerve
• It receives a branch which contains parasympathetic secretomotor fibers coming
from the pterygopalatine ganglion on their way to the lacrimal gland

73. The frontal nerve
• Largest of the branches of the ophthalmic nerve
• Enters the orbit through the tapered part of the superior orbital fissure, between the
lacrimal nerve outside and the trochlear nerve inside.
• Halfway along, it splits to form a small medial branch called the supratrochlear nerve
and a large lateral branch called the supraorbital nerve.
• Supratrochlear passes above the trochlea of the superior oblique muscle and
distributes to the medial 1/3 of the upper eyelid and the conjunctiva
• Supraorbital passes upwards and innervates the middle 1/3 of the upper eyelid and
the conjunctiva

74. The nasociliary nerve
• The most medial of the branches of the ophthalmic nerve
• Only one to reach the eyeball.
• Together with the ophthalmic artery, it crosses the optic nerve before travelling
obliquely between the medial rectus muscle below and the superior rectus and
superior oblique muscles above.
At the level of the anterior ethmoidal foramen, it splits to form two branches:
• The anterior ethmoidal nerve
• The infratrochlear nerve

75. • The anterior ethmoidal nerve, medial, which crosses the canal of the same
name with the corresponding artery, and then passes over the cribriform plate
of the ethmoid bone.
• The infratrochlear nerve, lateral, continues in the direction of the common
trunk. It splits to form rami going to the mucosae (the medial part of the
conjunctiva and the lacrimal ducts) and the skin (the medial part of the eyelid
and the root of the nose).

77. SURGICALAPPROACHES

78. Approaches to lateral orbit and orbital roof:
• Lateral brow
• Upper blepharoplasty
• Coronal approach

79. Approaches to orbital floor:
• Subciliary/ Subtarsal
• Transconjunctival approach
• Transantral approach

80. Approaches to Medial orbit:
• Lynch
• Transcaruncular approach

81. THANK YOU