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

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 height35 mm Entrance width40 mm Medial wall length / depth 45 mm Volume30 cc Distance from the back of the globe to the optic foramen 18 mm 45mm 35mm

SALIENT ANATOMICAL FEATURES 7 bones 6 contents 5 important relationships 4 walls 4 margins 4 important openings

v

MZSFELP Bones & walls

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?

Openings of the orbit Nasolacrimal canal Where? What passes through? Clinical significance Inferior orbital foramen Where? What passes through Clinical significance?

Sensory Nerve Supply of the Face

Orbital walls 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

Extraconal space Intraconal space Subperiosteal 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 Trauma mostly damages the medial wall & the floor (the weakest parts give way) The symptomotology of orbital diseases is reflective of its clinical anatomy