Orbit

Orbit

Horizontal entrance width – 40mmVertical entrance height – 35mmVolume – 30mgOrbital depth – 45-55mmDistance from back of globe to optic foramen- 18 mmOrbital segment of optic nerve – 25mm

ORBITAL RIM

Zygomatic bone – lateral margin. Frontal bone - superior margin.Maxillary bone – medial margin.Maxillary and zygomatic bones – inferior margin

Orbit

NASAL AND PARANASAL SINUSES

Roof of the Orbitfrontal bone and the lesser wing of the sphenoid. - the lacrimal gland fossa - contains the orbital lobe of lacrimal gland - the fossa for the trochlea of the superior oblique tendon (fovea) - supraorbital notch which transmits the supraorbital vessels and branch of the frontal nerve (V – I) supplies the skin and conjuctiva of the upper lid and scalp.

Roof of the Orbit is the strongest!

Lateral Wall of the OrbitZygomatic bone and the greater wing of the sphenoid, bordered by the superior and inferior orbital fissures. - the lateral orbital tubercle of Whitnall (frontozygomatic suture) – important points: lateral canthal ligament, the lateral rectus check ligament, the lateral horn of the levator aponeurosis, the suspensory ligament of the lower lid (Lockwood's ligament), the orbital septum, and the lacrimal gland fascia attach at Whitnall's tubercle

- meningeal foramen – conducts recurrent meningeal artery. This artery has connection with lacrimal artery from ophthalmic artery.

Lateral Wall of the Orbit zygomaticosphenoid suture - convenient breaking point for bone removal during lateral orbitotomy. zygomaticofacial and zygomaticotemporal canal –

Transmit 2 branches of the zygomatic nerve and vessels supplying the skinOn the forehead and cheek. Branch toLacrimal nerve (parasympatic fibers)From pterygopalatine ganglion

* Lateral wall is the srongest part !

Floor of the Orbitmaxillary, palatine, and zygomatic bones. (shortest) infraorbital groove and infraorbital canal - transmitthe infraorbital artery (branch of maxillary artery) and the maxillary division of the trigeminal nerve.

Medial Wall of the Orbitmaxilla, lacrimal, ethmoid, lesser wing of sphenoid.The thinnest portion - lamina papyracea - covers the ethmoid sinuses.

anterior and posterior ethmoidal foramina - branches of the ophthalmic artery and the nasociliary nerve. The location of these foramina is important when the surgeon gives an anterior ethmoidal nerve block for local anesthesia during medial orbitotomy. provide a potential route of entry into the orbit for infections and neoplasms from the sinuses.

Sphenopalatine foramen – sphenopalatine artery (branch of maxillary artery)

Medial Wall of the Orbit

SUPERIOR ORBITAL FISSURETransverse notch between greater and lesser wings of the sphenoid.Within the annulus of Zinn:

Superior and inferior divisions of the III CN– Sup. rectus, levator palpebrae / Inferior and Medial rectus, Inferior Oblique. Spincter (parasympathetic) pup.constriction.

The sixth cranial nerve (abducance)- Lateral rectus muscleNasociliary branch of the ophthalmic trigeminal nerve -

communicating branch to the ciliary ganglion, the long ciliary nerves, the posterior and anterior ethmoidal nerves. Than it becomes infratrochlear and nasal branches – supplies mucous of nose, skin and conjunctiva.Middle meningeal artery anastomosis with the ophthalmic artery may enter here, if not through its own foramen, more anteriorly in the roof.Most of the venous drainage from the orbit and the globe flow through the superior orbital fissure to the cavernous sinus.

SUPERIOR ORBITAL FISSUREOut of annulus of Zinn:

Frontal Nerve – V CN ophthalmic div supratrochlear(upper eyelid, medial forehead, and bridge of the nose) / supraorbital (forehead, upper eyelid, and scalp)

Lacrimal Nerve – V CN ophthalmic div communicates with the zygomatic branch of the maxillary nerve supplies lacrimal gland and conjunctiva.On the frontal rim it comunicates with filaments of the facial nerve

Trochlea (IV CN) – passess levator palpebrae superior than medily to superior rectus muscle and innervates superior oblique muscl

Optic Canal8-10 mm long, 5 to 7 mm wide.This canal is separated from the superior orbital fissure by the bony optic strust.The optic nerve (II CN)- derived from the diencephalon. 770,000 - 1.7 million nerve fibers, which are axons of the retinal ganglion cells of one retina. (part of CNS) Course and lengths of the visual fibers are intraocular (1 mm), intraorbital (25 mm), intracanalicular (5 to 9 mm), intracranial (16 mm)ophthalmic artery – I branch of the internal carotid artery, crosses above the optic nerve and provides the central retinal artery branch, 2-3 long posterior ciliary arteries, The terminal ophthalmic artery exits the orbit as the supratrochlear, dorsal nasal, and medial palpebral arteries.

Optic Canalsympathetic nerves – controls pupillary dilatation (pupil dilator muscle, function of the smooth muscles of the eyelids traveling along the intracavernous carotid artery.

INFERIOR ORBITAL FISSURE20-mm long foramen surrounded by sphenoid, zygomatic, maxillary, and palatine bones.Maxillary nerve from V CN. - exits the foramen rotundum and crosses the pterygopalatine fossa before entering the orbit through the inferior orbital fissure infraorbital nerve (infraorbital foramen) to the lower eyelid, cheek, and upper lip. zygomatic nerve – zygomaticotemporal and zygomaticofacial nerve, which exit the orbit using identically named foramen.Pterygopalatine ganglion nerve – (from maxillary neve) orbital branch supplies orbital periosteominferior ophthalmic vein - verticose, inf rectus, inf oblique, lac sac, eyelids IOV joins pterygoid venous plexus cavernous sinus

Oculomotor III CNMidbrain Lateral wall of cavernous sinus divides in 2 parts: posterior and inferior Superior Orbital fissureSuperior branch is smaller division. It passes medially over the optic nerve and supplies Superior Rectus muscle and superiio levator palpebrae muscle (opens eye). Symphatetic Fibers go with Superior Division to Sup. Levator palpebrae

Oculomotor III CNInf. Divison goes to 1.medial rectus 2.inferior rectus 3.inferior obliqueParasymphatetic fibers go along inferior oblique but do not end up here.On the way there is Ciliary Ganglion. From here ciliary ganglion gives rise to short ciliary neves, which enter in eyeball between sclera and choroidAnd goes to ciliaris muscle and constrictor pupillae to constrict the pupil

ophthalmic artery is a branch of internal carotid artery (cerebral part). optic nerve and ophthalmic artery move together through the optic canal and lies infrolateral to the optic nerve. after passing through the canal it goes upward and medially and moves on the upper part of medial wall. below it there is superior oblique muscle and trochlea nerve. once it reaches to the medial angle of the eye it divedes to terminal branches. 1. above the trochlea - supratrochlear artery2. below the trochlea - dorsal-nalas artery supplies nose going medially main ophthalimc artery has a branch - supra orbital artery which goes through supraorbital notch.

on the ethmoidal wall ther are 2 foramens - oneposteriorly and one anteriorly. posterior ethmoidal artery gives supply to ehtmoidal air sinus anterior ethmoidal artery to anterio ethmoidal canal and supplies ethmoidal air sinus.Central retinal branch - goes throug the eyebelow the optic nerve it has superior and inferiorbranches supplies the inner layer of retina. Moving to the lateral wall of the orbit - lacrimal artery - near lateral rectus makes recurrentMeningeal artery which comes back to superior orbital fisuure and comes out. it anastomosesswith middle meningeal artery. lacrimal branch supplies extraocular muscle.

lacrimal artery has branch which goes through the zygomatic bone by 2 foramens:1. zygomaticotemporal and 2. zygomaticofacial artery supplying the skin on the forehead and cheek. Some fo the branches goes to corneo scleral junctionmakes arterial major arterial ring of iris – anterior ciliary artery. – 7 small arteries supply conjunctiva,sclera

Supplies lacrimal gland and it has terminal branches - lateral palpebral branches for upper and lower eyelids thay make superior and inferior arcades.

posterior ciliary arteries comes from posterior side and goes through the sclera...Pterigo-palatine fossa comunicates with inferior orbital fissure. From maxillary artery one branch from inf. Orbital fissure, goes to the orbit and moves forward passess through a groove “infraorbital groove” and comes out as “infraorbital artery”, it supplies inferior rectus and inferior oblique muscles

Orbital Venous DrainageIn the upper part of the eye there is Superior Ophthalmic Vein. it starts behind the upper eyelid medial corner. It runs posteriorly with ophthalmic artery. Ethmoidal, Lacrimal and vortx veins drain to Sup.O.V. Through the medial part of the superior orbital fissure thay leave orbit and drain into cavernous sinus.Inferior Ophthalmic Vein receives verticose veins, veins from inferior rectus and oblique muscles. Passes through the inferior orbital fissure and end in pterygoid venous plexus or comunicates with Sup.O.V. and ends in the cavernous sinus.

Orbital Venous DrainageThere are connections between ophthalmic and facial veins. Facial vein from supraorbital and supratrochlear veins goes downs – Angular Vein – Connects firstly sup.O.V. than Inf.O.V.These connections are dangeorus, as there is no valve. Cavernous sinus thrombosis. Sup.O.V thrombosis and etc.

Orbital Lymphatic DrainageNo lymphatic vessels or lymph nodesPresence of lymphoid aggregates or fully formed lymph nodes are pathologic.Lymphatic system near orbit - cervical lymph channels

PeriorbitaMembrane wich covers the orbit bone.Firmly attached at the suture lines and fissures, elsewhere easily separated from the bone. Continuous with the dura of the optic nerve.Anteriorly, the periorbita is continuous with the orbital septum.Periorbita is extensively vascularized by interconnected vesels branches of the sensory intraorbital trigeminal nerve• provide resistance to the spread of infections and tumors from the

sinuses and bones into the orbit

Orbital FasciaFascia covering the globe - Tenon's capsule (the fascia bulbi) – fibrous membrane from optic nerve (thinnest) to conjunctiva. Closely applied to the globe and space between these structures is termed Tenon's space.Tunnel-like openings for extraocular muscles, in the areas of these openings, Tenon's capsule fuses with the intermuscular septal fascia.

Orbital FatThe orbital structures are surrounded by orbital fatThe infratrochlear nerve and the medial palpebral artery branch of the ophthalmic artery courses through the medial fat.

annulus of Zinn4 recti and sup, Oblique muscle, levator palpebrae superioris muscle originate from annulus of Zinn.lateral rectus muscle separates the superiororbital fissure into 2 compartments.Intraconal – (oculomotor foramen) oculomotor nerve divisions, the optic, the nasociliary and abducen nerves, ophthalmic arterExtraconal - trochlear, lacrimal, frontal nerves, and the superior ophthalmic vein.

The GlobeAttached to the eye: six extraocular muscles, the optic nerve, the long and short posterior ciliary nerves, the anterior and posterior ciliary arteries, and the vortex veinsvolume of the eye is about 6.5 cc (orbital volume29.7)

Anterior-posterior 24 mm

Vertical 23 mm

Horizontal 23.5 mm

ReferencesDuane's Clinical OphthalmologyAmerican academy: Orbit Eyelids and Lacrimal SystemJakobic’s Principles and Practice of OphthalmologyVaughan Asburys General Ophthalmology , 18th EditionHealth, Medcine and Anatomy Reference PicturesClinically Oriented Anatomy – MooreWikipedia

Zura Glonti 2017