Dr. Ayesha Abdullah
19.08.2015

By the end of this lecture the students would be able to;
“correlate the structural organization of the orbit with its functions and clinical significance”

• The orbital cavities are …………

Entrance height
Entrance width
35 mm
40 mm
Medial wall length / depth
45 mm
Volume 30 cc
Distance from the back of the globe to the optic foramen
18 mm
35mm
45mm
45mm

•
•
7-6-5-4
•
•
•
•

v

Bones
& walls
MZSF
ELP

Which orbit ?

IMPORTANT OPENINGS OF THE ORBIT
Optic Foramen
• Where?
• size?
• what passes through?
• Clinical significance?
Superior orbital fissure
• Where?
• What passes through?
• What is annulus of Zinn?
• Clinical significance?
Inferior orbital fissure:
• Where?
• What passes through?
• Clinical significance?

Nasolacrimal canal
• Where?
• What passes through?
• Clinical significance
Inferior orbital foramen
• Where?
• What passes through
• Clinical significance?

Roof
• Frontal bone and sphenoid lesser wing
• Lacrimal gland, trochlea
• Superior orbital notch
• Brain
Floor
• Zygomatic, maxilla and palatine bones.
• weak part
• Infraorbital groove & canal for the infraorbital nerve
• Maxillary sinus.

Medial Wall
• lacrimal, maxillary, ethmoid & sphenoid
• Thinnest wall
• Lamina papyrecea
• It separates the orbit from the nasal cavity, the ethmoidal and the sphenoidal sinuses
Lateral Wall
• Zygomatic & Sphenoid (greater wing)
• Stronger wall
• It separates the orbit from the (temporal fossa) and the brain

Roof

Medial wall
Floor

IMPORTANT RELATIONS OF THE ORBIT
1.
Brain : Orbit is closely related to the brain in relation to its roof and lateral wall.
2.
Para nasal sinuses: Orbit is intimately connected to the paranasal sinuses.
– Maxillaly sinus via the floor.
– Ethmoidal and sphenoidal sinus via the medial wall.
– Frontal sinus at the roof.
– Any infection can easily spread to the orbit from the sinuses.
3.
Nasal cavity: Nasal cavity is related to the orbit at its medial or inner wall & through the nasolacrimal duct
4.
Cavernous sinus via the veins of the orbit
5.
Pterygopalatine fossa via the inferior orbital fissure

Orbit as seen from above

Relations of the orbit to the paranasal sinuses :FS, frontal sinus; ES, ethmoidal sinus; MS , maxillary sinus; SS, sphenoid sinus- American Academy of Ophthalmology

CONTENTS OF THE ORBIT
1.
Eyeball & the optic nerve
2.
Muscles – To move the eyeball.
3.
Nerves –
– To move the muscles ( III, IV, VI).
– To carry different sensations ( V)
– parasympathetic innervation ( accommodation, pupillary constriction & lacrimal gland stimulation
– Sympathetic innervation ( pupillary dilatation, vasoconstriction, smooth muscles of the eye lids & hidrosis)

CONTENTS OF THE ORBIT
4.
Blood vessels ( branches of ophthalmic artery, superior & inferior ophthalmic veins)
5.
Fat & orbital fascia – For padding purposes & for smooth movements
6.
Most of the Lacrimal Apparatus (lacrimal gland
& part of the tear drainage system)

Lacrimal gland and the view of the orbit from the roof

Orbital fascia
• Periorbita
• Orbital septum
• Tenon’s capsule
• Fascial spaces intraconal extraconal subtenon subperiosteal

Subperiosteal space
Extraconal space
Intraconal space

Structure of the lids-AAO

RADIOGRAPHIC ANATOMY OF THE ORBIT

AXIAL CT SCAN

• Orbit is the protective casing for the delicate visual apparatus - the eyeball
• It is made up of 7 bones, has 4 margins, 4 walls/ boundaries, 4 important openings , 5 important relations & 6 contents
• Infection can spread to the brain from the orbit directly or through the haematogenous spread
• Trauma mostly damages the medial wall & the floor (the weakest parts give way)
• The symptomotology of orbital diseases is reflective of its clinical anatomy