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?
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
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
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) 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)
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 venous drainage Trauma mostly damages the medial wall & the floor ( the weakest parts give way) The symptomotology of orbital diseases is reflective of its clinical anatomy
References American Academy of Ophthalmology.Orbit, eyelids & lacrimal system. American Academy of Ophthalmology; 1997-98 Jack J Kanski. Clinical ophthalmology a systematic approach. 5 th ed;2003:557-89 Parsons’ diseases of the eye. Diseases of the adnexa-diseases of the orbit. 19 th ed. 2004; 505-524 Remington LA. Clinical Anatomy of the visual system. Bones of the skull & orbit. 1998; 123- 35