The document provides an overview of the anatomy of the orbit, including its walls, contents, surgical spaces, vascular and nervous supply. Some key points include: - The orbit is a pyramid-shaped cavity formed by 7 bones and divided into 4 walls - medial, lateral, roof and floor. - It contains the eyeball, extraocular muscles, nerves, vessels and orbital fat. - There are 4 surgical spaces - subperiosteal, peripheral, central and subtendon. - The orbit receives its blood supply from the ophthalmic artery and drains via the superior ophthalmic vein. - Sensory innervation is from the ophthalmic and maxillary nerves and motor inner

1. DR. STUTI SOMANI AGARWAL

2. ORBIT:
 It is situated between the Anterior cranial fossa above
and the maxillary sinus below.
 The 2 bony orbits are quadrangular truncated
pyramids.
 Each orbit is formed by 7 bones: Frontal, Ethmoid,
Lacrimal, Palatine, Maxilla, Zygomatic and Sphenoid.
 The medial walls are parallel to each other.
 The lateral walls are at 45 degree to medial.
 The 2 lateral walls are at 90 degrees to one another.

3. Cont.
 The depth of each orbit is 42mm along the medial wall and
50 mm along the lateral wall.
 Width of the base of orbit is 40mm and height is 35mm.
 Orbital index = (height/width)* 100
 This Index is important for racial variations.
 The intra-orbital width is 25mm.
(the distance between 2 medial walls)
 The extra orbital width is 100mm.
(the distance between the 2 lateral walls)
 Volume of the orbit is 29ml.
 Ratio of vol. of orbit to eyeball is 4.5:1

4. BASIC LAYOUT:

5. WALLS OF THE ORBIT
A) MEDIAL WALL:
 Quadrilateral shape
 Thinnest wall
 Formed by frontal process of maxilla, lacrimal bone,
orbital plate of ethmoid, body of the sphenoid.
 Anterior part has the lacrimal fossa which has the
lacrimal sac.
 The lacrimal fossa is bounded anteriorly by the anterior
lacrimal crest of maxilla and posteriorly by the post
lacrimal crest of lacrimal bone.
 Behind the post. lacrimal crest are attached the horner’s
muscle, septum orbitale & check ligament of medial
rectus.

6. CLINICAL IMPORTANCE:
 It is the thinnest wall.
 Thus, ethmoiditis is a common cause of orbital
celluliis in children.
 Easily fractured during orbitotomy operations and
injury.
 During surgeries in this area, hemorrhage is a very
common complication due to the injury to the
ethmoidal vessels.

7. B)LATERAL WALL:
 Triangular in shape.
 Formed anteriorly by the zygomatic, posteriorly by the greater
wing of sphenoid.
 On the posterior part of the lateral wall is a small projection
(spina recti lateralis) which gives origin to the lateral rectus
muscle.
 A zygomatic groove and a foramina lie anteriorly (through
which runs the zygomatic nerve and vessels)
 Lateral tubercle of whitnall, is a projection on the ant. Part of
the wall, which gives attachment to the check ligament of
lateral rectus and suspensory ligament of eyeball.
 Lateral wall is separated posteriorly from the roof by the
superior orbital fissure and from the floor by the inferior
orbital fissure.

8. CLINICAL IMPORTANCE:
 Lateral wall protects only the posterior half of the
globe, as it doesnt cover the anterior half.
 Thus, retrobulbar tumours can be easily palpated from
the lateral approach than the nasal.
 Due to anatomical advantages- thick, tough, no
important vessels, no foramina- the lateral wall is of
choice during orbital surgeries.
 It is the strongest part of the orbit.

9. C)ROOF:
 Triangular shape.
 Formed by the orbital plate of frontal bone and lesser
wing of sphenoid.
 Antero-lateral part of the roof has a depression called
the fossa of the lacrimal gland.
 The fovea for the pulley of the superior oblique
muscle (trochlear fossa) is a small depression,
situated close to the orbital margin, at the junction of
the roof and the medial wall.

10. CLINICAL IMPORTANCE:
 No important nerve or vessel piercing or perforating
the roof, thus easy approach in transfrontal
orbitotomy.
 Superior wall is thin throughout, thus the periorbita
easily peels away from the undersurface.

11. D)FLOOR:
 Triangular shape.
 Shortest of all walls.
 Formed by the orbital surface of the maxilla medially, orbital
surface of zygomatic latrally, palatine bone posteriorly.
 Posterior part of the floor and lateral wall separated by the
inferior orbital fissure.
 Inferior orbital fissure is continuous anteriorly as a groove-
the infraorbital groove which extends anteriorly as acanal,
which opens into the infraorbital foramen.
 This foramen transmits the infra orbital nerve and vessels.

12. CLINICAL IMPORTANCE:
 Floor is quite thin and is involved in blow out
fractures.
 Easily invaded by tumours of maxillary antrum.
 Best visualised by PA view of Xray.

13. BASE OF THE ORBIT:
 It is the anterior open end of the orbit.
 Bounded by the orbital margins.
 The margin is formed by a ring of compact bone and gives
attachment to the septum orbitale.
THE SUPERIOR ORBITAL MARGIN is formed by the arch of the
frontal bone.
 Its lateral 2/3rd is sharp and medial 1/3rd is rounded.
 At this junction is the highest point of the arch, where the supra-
orbital notch lies.
 About 10mm medial to this notch lies the supratrochlear groove,
which transmits the supratrochlear nerve and artery.

14. THE LATERAL ORBITAL MARGIN is formed by the
zygomatic process of the frontal and zygomatic bone.
 It is the strongest part.
THE INFERIOR ORBITAL MARGIN is formed by the
zygomatic bone laterally and maxilla medially.
 Medially, it becomes continuous with the anterior
lacrimal crest.
THE MEDIAL ORBITAL MARGIN is formed by the anterior
lacrimal crest below on the frontal process of maxilla and
frontal bone above.
 Upper part becomes continuous with the pposterior
lacrimal crest.

15. APEX OF THE ORBIT:
 It is the posterior end of the orbit.
 Where the 4 walls converge.
 It has 2 orifices the optic canal and superior orbital
fissure.
 Both these orifices are present in the sphenoid bone,
where the lesser wing, greater wing and body meet
each other.

17. A) OPTIC CANAL:
 Connects the orbit to the medial cranial fossa.
 Transmits the optic nerve(surrounded by the
meninges) and the ophthalmic artery.
 avg,. Length is 6 to 11 mm
 Lateral wall is the shortest
 Medial is the longest.
 Tumours like the optic nerve glioma and meningioma
may lead to unilateral enlargement of the optic canal.

18. B) SUPERIOR ORBITAL FISSURE:
 A comma shaped aperture in the orbital cavity
 It is bounded by the lesser wing and greater wing.
 Situated lateral to the optic foramen at the orbital
apex.
 The fissure is divided into
3 parts by the
common tendinous
ring.

19.  CONTENTS OF THE SUPERIOR ORBITAL FISSURE:
 A) Upper part
 B) Middle part
 C) Lower part

21. PERIORBITA: It is the periosteum lining the surface of the orbital bones.
 Generally it is loosely adherent to the bone.
 But is firmly adherent at the orbital margin,
superior and inferior orbital fissures,
the optic canal, lacriaml fossa and
the sutures.
 It splits into two layers, which reunites
at the ant. lacrimal crest.
 Between the 2layers is the lacrimal sac.
 At the apex, the periorbita
thickens to form the common
tendinous ring of Zinn.

22.  ORBITAL FASCIA:
 It is a thin connective tissue membrane lining the various intraorbital
structures.
 Though it is one tissue, it has been described under the headings of fascia
bulbi, muscular sheaths, intermuscular septa, membranous expansion of
extra ocular muscles and ligaments of Lockwood.
 FASCIA BULBI or TENON’S CAPSULE, envelops the globe from the limbus to
the optic disc.
 Tenon’s capsule is separated from the sclera by episcleral space (tenon’s
space), which can be readily injected.
 The lower part of the fascia bulbi is thckened and takes part in the formation
of a sling or hammock on which the globe rests, SUSPENSORY LIGAMENT
OF LOCKWOOD.
 FASCIAL SHEATHS OF EXTRAOCULAR MUSCLES are tubular reflections,
which clothes the muscle like a glove.
 MUSCULAR SHEATHS sends expansions to the surrounding structures,
forming the medial and lateral check ligaments, rectus muscle pulleys etc.

23. SURGICAL SPACES IN THE ORBIT:
1)SUBPERIOSTEAL SPACE:
 Potential space between the orbital bones and the periorbita,
limited anteriorly, by the strong adhesions of the periorbita to
the orbital rim.
 Tumours from the bones are blocked by the periorbita from
involving the eye.
2) PERIPHERAL ORBITAL SPACE:
 It is the anterior space.
 Bounded peripherally by periorbita, internally by the extraocular
muscles with their intermuscular septum and anteriorly by the
septum orbitale (including tarsal plate and tarsal ligaments).
 Posteriorly it merges with the central space.
 Tumours in this space result in eccentric proptosis.

24. 3) CENTRAL SPACE:
 It is also called the muscular cone or posterior or
retrobulbar space.
 Bounded anteriorly by Tenon’s capsule lining the
back of the eyeball, peripherally by the
extraocular recti muscle and their intermuscular
septa.
 Contents of this space: optic nerve and its
meninges, superior and inferior divisions of the
oculomotor nerve, abducent nerve, nasociliary
nerve,ciliary ganglion, ophthalmic artery, sup.
ophthalmic vein and the central orbital fat.
 Tumours in this area cause axial proptosis.

25. 4)SUBTENON SPACE:
 Potential space between the sclera and the Tenon’s
capsule.
 Pus collection in this space is drained by the incision
of the Tenon’s capsule through the conjunctiva.

27. CONTENTS OF THE ORBIT:
 Eyeball
 Muscles: 4 recti, 2 obliques, LPS, Muller’s muscle.
 Nerves: 2,3,4,6, branches of ophthalmic and maxillary
divisions of 5th nerve.
 Vessels: Ophthalmic artery and its branches,
infraorbital vessels, orbital branch of middle
meningeal artery, superior and inferior ophthalmic
vein.
 Orbital fat, reticular tissue, orbital fascia.
 Lacrimal gland and lacrimal sac.

28. ARTERIAL SUPPLY OF ORBIT:
 Primarily from the ophthalmic artery, which is a branch of the
Internal carotid artery.
 Smaller contributions from the Internal maxillary and facial
branches of the External carotid artery.
 The ophthalmic artery travels beneath the optic nerve, through
the dura mater along the optic canal to enter the orbit.
 The major branches of the ophthalmic artery are a) branches to
the extraocular muscles. b) central retinal artery (to optic nerve
and retina). c)Post. ciliary aartery (long to the anterior segment
and short to the choroid)
 Terminal branches of the ophthalmic artery travel anteriorly and
form an anastomosis with ext. carotid artery in the face and
periorbital region.

29. VENOUS DRAINAGE:
 Superior Ophthalmic vein provides the main venous
drainage of the orbit.
 This vein originates from the supero-nasal quadrant of
the orbit and extends posteriorly through the superior
orbital fissure into the cavernous sinus.
 Many anastomoses occur anteriorly with the vein if the
face as well as the posteriorly with the pterygoid
plexus.

30. NERVES OF THE ORBIT:
A) SENSORY: Ophthalmic nerve and its lacrimal,
frontal, nasociliary branches.
Maxillary nerve.
B) MOTOR: Oculomotor nerve.
Trochlear nerve.
Abducent nerve.
C) PARASYMPATHETIC