REVIEW OF CLINICAL ANATOMY & PHYSIOLOGY OF THE ORBIT Dr. Ayesha Abdullah 17.08.2016

By the end of this lecture the students would be able to; LEARNING OUTCOME 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”

ANATOMY OF THE ORBIT The orbital cavities are …………

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

SALIENT ANATOMICAL FEATURES 7 bones 6 contents 5 important relationships 4 walls 4 margins 4 important openings 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 What passes through? What is annulus of Zinn? Inferior orbital fissure: Optic Foramen: This is an important opening at the back of maximum diameter of 6.5mm ( adults). It is present at the apex of the orbit. It opens into the optic canal, which contains the optic nerve, ophthalmic artery & sympathetic nerves. So the optic nerve enters the orbit through the optic foramen. Optic foramen enlargement can occur with tumour of the optic nerve like optic nerve glioma. Trauma can cause fracture of the optic canal & damage the optic nerve. What passes through Superior orbital fissure The 3rd cranial nerve - Oculomotor The 4th cranial nerve – Trochlear Branches of 5th cranial nerve (Lacrimal nerve, Frontal nerve,Nasociliary nerve) 6th cranial nerve – Abducent. Superior ophthalmic vein en route to cavernous sinus Edges of this fissure give attachment to an important ligament that gives rise to the muscles of the eyeball called the annulus of zinn. Inferior orbital fissure: This is an other cleft, which separates the lateral wall and the floor it communicates with the pterygopalatine fossa & the pterygoid venous plexus. Important structures passing through it are: Braches of the 5th nerve Some veins and arteries

Openings of the orbit Inferior orbital foramen What passes through Nasolacrimal canal Where? What passes through? Clinical significance Inferior orbital foramen What passes through Clinical significance? Nasolacrimal canal It extends from the lacrimal fossa to the inferior turbinate in the nasal cavity Other openings are the ehtmoidal foramina & foramina of the zygomaticotemporal & zygomaticofacial canals

Sensory Nerve Supply of the Face

Orbital walls Frontal bone and sphenoid lesser wing 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 Brain Para nasal sinuses Nasal cavity Cavernous sinus Pterygopalatine fossa Brain : Orbit is closely related to the brain in relation to its roof and lateral wall. 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. Nasal cavity: Nasal cavity is related to the orbit at its medial or inner wall & through the nasolacrimal duct Cavernous sinus via the veins of the orbit 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 Eyeball & the optic nerve Muscles – To move the eyeball. 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 Blood vessels ( branches of ophthalmic artery, superior & inferior ophthalmic veins) Fat & orbital fascia – For padding purposes & for smooth movements 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

VIEWS : AXIAL VIEWS RADIOGRAPHIC ANATOMY OF THE ORBIT

CORONAL VIEW

SAGITTAL VIEW

AXIAL CT SCAN

Summary 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- Orbital septum is a barrier to infection Trauma mostly damages the medial wall & the floor (the weakest parts give way) The symptomotology of orbital diseases is reflective of its clinical anatomy