Orbital Anatomy

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Orbital and Ocular AnatomyOrbital and Ocular Anatomy

Abdulrahman Al-Muammar, MD, FRCSC

King Saud University



Periorbital Sinus

es

Periorbital Sinus

es

The eyes lie within two bonyThe eyes lie within two bonyorbits, located on either side of orbits, located on either side of the root of the nose. the root of the nose.

They border the nasal cavityThey border the nasal cavity

anteriorly and the ethmoidal air anteriorly and the ethmoidal air cells and the sphenoid sinuscells and the sphenoid sinusposteriorly. posteriorly.

The lateral walls border the The lateral walls border the middle cranial, temporal, andmiddle cranial, temporal, andpterygopalatine fossae. pterygopalatine fossae.

Superior to the orbit ar e the Superior to the orbit ar e the

anterior cranial fossa and the anterior cranial fossa and the frontal and supraorbital sinus. frontal and supraorbital sinus.

The maxillary sinus and the The maxillary sinus and the palatine air cells ar e locatedpalatine air cells ar e locatedinf eriorly.inf eriorly.



Orbital Volume

Orbital Volume

The volume of each adult orbitThe volume of each adult orbitis slightly less than 30 ccis slightly less than 30 cc

The orbital entrance averagesThe orbital entrance averagesabout 35 mm in height and 45about 35 mm in height and 45

mm in width. The maximummm in width. The maximumwidth is about 1 cm (behind the width is about 1 cm (behind the anterior orbital margin)anterior orbital margin)

In adults, the depth of the orbitIn adults, the depth of the orbitvaries from 40 to 45 mm fromvaries from 40 to 45 mm fromthe orbital entrance to the orbitalthe orbital entrance to the orbitalapexapex

Both race

and sex aff

ect

each of Both rac

eand s

ex aff

ect

each of these measur ements.these measur ements.



Bony OrbitBony OrbitSeven bones make Seven bones make

up the bony orbit:up the bony orbit:

FrontalFrontal

ZygomaticZygomatic

MaxillaryMaxillary

EthmoidalEthmoidal

SphenoidSphenoid

LacrimalLacrimal

PalatinePalatine



Orbital Roof Orbital Roof The orbital roof The orbital roof

formed from bothformed from both

the orbital plate of the orbital plate of the frontal bone andthe frontal bone and

the lesser wing of the lesser wing of

the sphenoid bone.the sphenoid bone.

Lacrimal glandLacrimal gland

Fovea trochlearisFovea trochlearis



Medial Orbital WallM

edial Orbital Wall

Then medial wall of the Then medial wall of the orbit is formed from four orbit is formed from four bones:bones:

Frontal process of the Frontal process of the maxillarymaxillary

LacrimalLacrimal

Orbital plate of the Orbital plate of the ethmoidalethmoidal

Lesser wing of the Lesser wing of the sphenoidsphenoid

Lacrimal fossaLacrimal fossa

Lamina papyraceaLamina papyracea



Orbital Floor Orbital Floor The floor of the orbitThe floor of the orbitis formed from thr ee is formed from thr ee

bones:bones:MaxillaryMaxillary

PalatinePalatine

Orbital plate of the Orbital plate of the zygomaticzygomatic

Infraorbital grooveInfraorbital groove

Inf erior oblique Inf erior oblique musclemuscle



Lateral Orbital WallLat

eral Orbital Wall

Formed from twoFormed from twobones:bones:

ZygomaticZygomaticGr eater wing of the Gr eater wing of the sphenoidsphenoid

Thickest andThickest andstrongeststrongest

Lateral orbitalLateral orbitaltubercle (Whitnall¶stubercle (Whitnall¶stubercle)tubercle)



Orbital ForaminaOrbital ForaminaThe optic foramenThe optic foramen

The supraorbital foramen, or The supraorbital foramen, or notchnotch

The anterior ethmoidalThe anterior ethmoidalforamenforamen

The posterior ethmoidalThe posterior ethmoidalforamenforamen

The zygomatic foramenThe zygomatic foramen

Nasolacrimal ductNasolacrimal ductInfraorbital canalInfraorbital canal

Superior orbital fissur eSuperior orbital fissur e

Inf erior orbital fissur eInf erior orbital fissur e



Extraocular MusclesExtraocular Muscl

es

The four r ecti andThe four r ecti and

two oblique musclestwo oblique muscles

All ar e supplied by All ar e supplied byoculomotor nerve IIIoculomotor nerve III

except superior except superior

oblique (Trochlear oblique (Trochlear

N) and lateral r ectusN) and lateral r ectus(Abducens)(Abducens)



Optic nerve

Optic nerve

The optic nerve The optic nerve

consists of mor e consists of mor e

than 1 million axonsthan 1 million axonsthat originate in the that originate in the

ganglion cell layer of ganglion cell layer of

the r etina andthe r etina and

extend toward the extend toward the occipital cortexoccipital cortex



Optic Nerve

Optic Nerve

The optic nerve may be dividedThe optic nerve may be dividedinto the following topographicinto the following topographicar eas:ar eas:

Intraocular portion of the opticIntraocular portion of the optic

ne

rve: optic disc, or n

erve n

erve: optic disc, or n

erve head; pr elaminar; and laminar head; pr elaminar; and laminar

portionsportions

Intraorbital portion (locatedIntraorbital portion (locatedwithin the muscle cone)within the muscle cone)

Intracanalicular portion (locatedIntracanalicular portion (located

within the optic canal)within the optic canal)

Intracranial portion (ending inIntracranial portion (ending inthe optic chiasm)the optic chiasm)



Optic ChiasmOptic ChiasmThe chiasm measur esThe chiasm measur esapproximately 12 mm wide,approximately 12 mm wide,8 mm long in the 8 mm long in the anteroposterior dir ection,anteroposterior dir ection,

and 4 mm thick. The exactand 4 mm thick. The exactlocation of the chiasm withlocation of the chiasm withr espect to the sella isr espect to the sella isvariable. Most of the time it isvariable. Most of the time it isdir ectly superior dir ectly superior

Within the chiasm, the fibersWithin the chiasm, the fiberscoming from the nasal r etinacoming from the nasal r etina(approximately 53% of total(approximately 53% of totalfibers) cross to the opposite fibers) cross to the opposite side to join the side to join the corr esponding contralateralcorr esponding contralateralfibersfibers



Optic TractOptic TractEach optic tractEach optic tractcontains ipsilateralcontains ipsilateraltemporal andtemporal and

contralateral nasalcontralateral nasalfibers from the opticfibers from the opticnerves . Fibers (bothnerves . Fibers (bothcrossed and uncrossed)crossed and uncrossed)from the upper r etinalfrom the upper r etinal

projections travelprojections travelmedially in the opticmedially in the optictract; lower projectionstract; lower projectionsmove laterally. move laterally.



Lateral g

eniculat

ebodyLat

eral g

eniculat

ebody

The lateral geniculate body,The lateral geniculate body,or nucleus, is the synapticor nucleus, is the synapticzone for the higher visualzone for the higher visual

proje

ctionsproje

ctionsIt has six alternating layersIt has six alternating layersof gray and white matter . of gray and white matter . Layers 1, 4, and 6 of the Layers 1, 4, and 6 of the lateral geniculate bodylateral geniculate bodycontain axons from the contain axons from the

contralate

ral optic ne

rve.

contralate

ral optic ne

rve.

Layers 2, 3, and 5 arise fromLayers 2, 3, and 5 arise fromthe ipsilateral optic nervethe ipsilateral optic nerve



Optic radiationsOptic radiationsThe optic radiations connectThe optic radiations connectthe lateral geniculate bodythe lateral geniculate bodywith the cortex of the with the cortex of the occipital lobeoccipital lobe

The fibers of the opticThe fibers of the opticradiations leave the lateralradiations leave the lateralgeniculate body and rungeniculate body and runaround the temporal horn of around the temporal horn of the lateral ventricle,the lateral ventricle,

approaching the

ante

rior tipapproaching the

ante

rior tipof the temporal lobe (the soof the temporal lobe (the so--called loop of Meyer)called loop of Meyer)



Visual cortexVisual cort

ex

The visual cortex, the thinnestThe visual cortex, the thinnestar ea of the human cer ebralar ea of the human cer ebralcortexcortex

Macular function is extr emelyMacular function is extr emely

well r epr esented in the visualwell r epr esented in the visualcortex and occupies the mostcortex and occupies the mostposterior position at the tip of posterior position at the tip of the occipital lobe the occipital lobe

The posterior cer ebral artery, aThe posterior cer ebral artery, abranch of the basilar artery,branch of the basilar artery,supplies the visual cortexsupplies the visual cortexalmost exclusively. The bloodalmost exclusively. The bloodsupply to the occipital lobe doessupply to the occipital lobe doesshow anatomical variation,show anatomical variation,however, with the middle however, with the middle cer ebral artery making acer ebral artery making acontribution in some persons.contribution in some persons.



Cranial Nerve

III (Oculomotor)Cranial Nerve

III (Oculomotor)It supplies all the extraocular musclesIt supplies all the extraocular muscles

except the superior oblique and the except the superior oblique and the

lateral r ectuslateral r ectus

It also carries cholinergic innervation toIt also carries cholinergic innervation to

the pupillary sphincter and the ciliarythe pupillary sphincter and the ciliary

musclemuscle



Cranial Nerve

IIICranial Nerve

IIIThe CN III nucleus consists of severalThe CN III nucleus consists of several

distinct, large motor cell subnuclei, eachdistinct, large motor cell subnuclei, each

of which subserves the extraocular of which subserves the extraocular muscle it innervatesmuscle it innervates

The Edinger The Edinger--Westphal nucleus providesWestphal nucleus provides

the parasympathetic pr eganglionicthe parasympathetic pr eganglioniceff er ent innervation to the ciliary muscle eff er ent innervation to the ciliary muscle

and pupillary sphincter and pupillary sphincter



Cranial Nerve

IIICranial Nerve

IIICN III usually divides intoCN III usually divides intosuperior and inf erior superior and inf erior divisions after passingdivisions after passingthrough the annulus of Zinnthrough the annulus of Zinnin the orbitin the orbit

The superior division of CNThe superior division of CNIII innervates the superior III innervates the superior r ectus and levator palpebrae r ectus and levator palpebrae muscles. The larger inf erior muscles. The larger inf erior

division splits into thr ee

division splits into thr ee

branches to supply the branches to supply the medial and inf erior r ectusmedial and inf erior r ectusmuscles and the inf erior muscles and the inf erior oblique.oblique.



Cranial Nerve

IIICranial Nerve

IIIThe parasympatheticThe parasympatheticfibers wind around the fibers wind around the periphery of the nerveperiphery of the nerve

Enter the inf erior Enter the inf erior division, and course division, and course through the branch thatthrough the branch thatsupplies the inf erior supplies the inf erior oblique muscle. Theyoblique muscle. They

join the ciliary ganglion join the ciliary ganglion

They synapse with the They synapse with the postganglionic fibers,postganglionic fibers,which emerge as manywhich emerge as manyshort ciliary nervesshort ciliary nerves



Cranial Nerve

IV (Trochlear)Cranial N

erve

IV (Trochlear)

Cranial nerve IV has the Cranial nerve IV has the longest intracranial courselongest intracranial course

The CN IV the only cranialThe CN IV the only cranial

nerve

that is comple

te

lynerve

that is comple

te

lydecussated and the onlydecussated and the onlymotor nerve to exit dorsallymotor nerve to exit dorsallyfrom the nervous system. from the nervous system.

CN IV enters the orbitCN IV enters the orbitthrough the superior orbitalthrough the superior orbital

fissur e outside the annulusfissur e outside the annulusof Zinn and runs superiorlyof Zinn and runs superiorlyto innervate the superior to innervate the superior oblique muscleoblique muscle



Cranial Nerve

V (Trigeminal)Cranial N

erve

V (Trigeminal)

The largest cranial nerveThe largest cranial nerve

Possesses both sensory and motor divisionsPossesses both sensory and motor divisions

The sensory portion subserves the gr eater The sensory portion subserves the gr eater part of the scalp, for ehead, face, eyelids, eye,part of the scalp, for ehead, face, eyelids, eye,

lacrimal gland, extraocular muscles, ear, duralacrimal gland, extraocular muscles, ear, dura

mater, and tonguemater, and tongue

The motor portion innervates the muscles of The motor portion innervates the muscles of

mastication through branches of the mastication through branches of the

mandibular divisionmandibular division



Divisions of Cranial N

erve

VD

ivisions of Cranial Nerve

VOphthalmicOphthalmic

FrontalFrontal

LacrimalLacrimalNasociliaryNasociliary

MaxillaryMaxillary

Mandibular Mandibular



Cranial Nerve

VI (Abducens)Cranial N

erve

VI (Abducens)

The nucleus of cranial nerve VI is situated inThe nucleus of cranial nerve VI is situated in

the floor of the fourth ventricle, beneath the the floor of the fourth ventricle, beneath the

facial colliculus, in the caudal ponsfacial colliculus, in the caudal ponsCN VI runs below and lateral to the carotidCN VI runs below and lateral to the carotid

artery and may transiently carry sympatheticartery and may transiently carry sympathetic

fibers from the carotid plexusfibers from the carotid plexus

It passes through the superior orbital fissur e It passes through the superior orbital fissur e

within the annulus of Zinn and innervates the within the annulus of Zinn and innervates the

lateral r ectus muscle on its ocular surfacelateral r ectus muscle on its ocular surface



Arterial syst

em Art

erial syst

em

Internal carotid artery

Ophthalmic artery

Central r etinal A

Short post ciliary A

Long post ciliary A

Anterior ciliary A

Lacrimal A

Superior muscular A

Inf erior muscular A

Posterior ethmoidal A

Anterior

ethmoidal ASupraorbital A

Supratrochlear A



Venous syst

emV

enous syst

em

Central r etinal V

Superior vortex V

Superior episcleral plexus

Inf erior vortex V

Inf erior episcleral plexus

Pterygoid plexus

Superior

ophthalmic V

Cavernous

sinus

Jugular v



The

Eye

The

Eye

The adult humanThe adult human

eye averages 24eye averages 24

mm in diameter mm in diameter The eye r eachesThe eye r eaches

maximum size maximum size

befor e puberty. The befor e puberty. The

transverse verticaltransverse verticaldiameter is lessdiameter is less

variable.variable.



CorneaCorn

ea

The cornea occupies the The cornea occupies the center of the anterior pole of center of the anterior pole of the globe. In the adult, itthe globe. In the adult, itmeasur es about 12 mm inmeasur es about 12 mm inthe horizontal meridian andthe horizontal meridian andabout 11 mm in the verticalabout 11 mm in the vertical

The cornea is transpar entThe cornea is transpar entand form a positive lens of and form a positive lens of about 40 D and constitute about 40 D and constitute the main r efractive elementthe main r efractive elementof the eyeof the eye



CorneaCorn

ea

EpitheliumEpithelium

Bowman¶s layer Bowman¶s layer

StromaStroma

Descemet¶sDescemet¶s

membranemembrane

EndotheliumEndothelium



ScleraScl

era

Sclera is opaque Sclera is opaque and whiteand white

The sclera coversThe sclera coversthe posterior four the posterior four fifths of the surface fifths of the surface of the globe, with anof the globe, with ananterior opening for anterior opening for the cornea and athe cornea and aposterior opening for posterior opening for the optic nervethe optic nerve



LimbusLimbusTransition zone Transition zone

between the between the

peripheral corneaperipheral corneaand the anterior and the anterior

sclerasclera



ConjunctivaConjunctivaMucous membrane withMucous membrane withnon keratinizednon keratinizedsquamous epitheliumsquamous epithelium

and goblet cellsand goblet cellsThin, richy vascularizedThin, richy vascularizedsubstantia propriasubstantia propria

Can be divided intoCan be divided intothr ee geographic zones:thr ee geographic zones:

PalpebralPalpebral

FornicealForniceal

Bulbar Bulbar



Anterior chamb

er Ant

erior chamb

er

The anterior chamber isThe anterior chamber isborder ed anteriorly byborder ed anteriorly bythe cornea andthe cornea and

posteriorly by th

eirispost

eriorly by th

eirisdiaphragm and the pupildiaphragm and the pupil

The depth of the The depth of the anterior chamber variesanterior chamber varies

The anterior chamber isThe anterior chamber isfilled with aqueousfilled with aqueoushumor, which ishumor, which isproduced by the ciliaryproduced by the ciliaryepitheliumepithelium



Anterior chamb

er Ant

erior chamb

er

The fluid passes through the pupilThe fluid passes through the pupilapertur e and drains chiefly by the apertur e and drains chiefly by the conventional pathway through the conventional pathway through the trabecular meshworktrabecular meshwork

The anterior chamber angle, whichThe anterior chamber angle, which

lies at the junction of the cornea andlies at the junction of the cornea andthe iris, consists of the followingthe iris, consists of the followingstructur es :structur es :

Schwalbe's lineSchwalbe's line

Schlemm's canal and the trabecular Schlemm's canal and the trabecular meshworkmeshwork

Scleral spur Scl

eral spur

Anterior border of the ciliary body Anterior border of the ciliary body



LensL

ens

The lens is a biconvexThe lens is a biconvexstructur e located dir ectlystructur e located dir ectlybehind the posterior behind the posterior chamber and pupilchamber and pupil

It is the lesser of the twoIt is the lesser of the twor efractive elements in the r efractive elements in the dioptric systemdioptric system

The equatorial diameter inThe equatorial diameter inadult is about 9adult is about 9--10 mm10 mm

The anteroposterior width of The anteroposterior width of

the

le

ns is about 6 mmthe

le

ns is about 6 mmThe lens has certain unusualThe lens has certain unusualf eatur es. It lacks innervationf eatur es. It lacks innervationand is avascular . and is avascular .



Uveal Tract

Uveal Tract

The uveal tract is the The uveal tract is the

main vascular main vascular

compartment of the compartment of the

eye. It consists of thr ee eye. It consists of thr ee

parts:parts:

IrisIris

Ciliary body (located inCiliary body (located in

the anterior uvea)the anterior uvea)

Choroid (located in the Choroid (located in the

posterior uvea)posterior uvea)



IrisIris



Ciliary BodyCiliary BodyThe ciliary body, whichThe ciliary body, whichis triangular in crossis triangular in crosssection. The apex of the section. The apex of the

ciliary body is dir ectedciliary body is dir

ectedposteriorly toward the posteriorly toward the

ora serrata. Its base ora serrata. Its base gives rise to the iris. gives rise to the iris. The only attachment of The only attachment of the ciliary body to the the ciliary body to the

sclera is at its base, viasclera is at its base, viaits longitudinal muscle its longitudinal muscle fibers, wher e they insertfibers, wher e they insertinto the scleral spur .into the scleral spur .



Ciliary bodyCiliary bodyThe ciliary body hasThe ciliary body hasthr ee principalthr ee principal

functions:functions:aqueous humor aqueous humor formation and lensformation and lensaccommodationaccommodation

It also plays a role inIt also plays a role in

the trabecular andthe trabecular anduveoscleral outflowuveoscleral outflowof aqueous humor of aqueous humor

Accommodation Accommodation



ChoroidChoroidThe choroid, the posterior The choroid, the posterior portion of the uveal tract,portion of the uveal tract,nourishes the outer portion of nourishes the outer portion of the r etina. It averages 0.25 mmthe r etina. It averages 0.25 mmin thickness and consists of in thickness and consists of thr ee layers of vessels:thr ee layers of vessels:

The choriocapillaris, the The choriocapillaris, the innermost layer innermost layer

A middle layer of small vessels A middle layer of small vessels

An outer layer of large vessels An outer layer of large vessels



Re

tinaRe

tinaThe fundus is the part of the The fundus is the part of the eye that is visible oneye that is visible onophthalmoscopy, includingophthalmoscopy, includingthe r etina and its vesselsthe r etina and its vesselsand the optic nerve head (or and the optic nerve head (or optic disc)optic disc)

The macula, 5The macula, 5± ±6 mm in6 mm indiameter, lies between the diameter, lies between the temporal vascular arcades. temporal vascular arcades. At the macula's center lies At the macula's center liesthe fovea, rich in cones andthe fovea, rich in cones andr esponsible for color visionr esponsible for color visionand the highest visual acuityand the highest visual acuity



Vitr e

ousVitr e

ousThe vitr eous cavity occupies four The vitr eous cavity occupies four fifths of the volume of the globefifths of the volume of the globe

The transpar ent vitr eous humor isThe transpar ent vitr eous humor isimportant to the metabolism of the important to the metabolism of the intraocular tissues because itintraocular tissues because it

provides a route for metabolitesprovides a route for metabolitesused by the lens, ciliary body, andused by the lens, ciliary body, andr etinar etina

Its volume is close to 4.0 mlIts volume is close to 4.0 ml Although it has a gel Although it has a gel--like structur e,like structur e,the vitr eous is 99% water the vitr eous is 99% water

Its viscosity is approximately twice Its viscosity is approximately twice that of water, mainly because of the that of water, mainly because of the

pr e

se

nce

of the pr

ese

nce

of the mucopolysaccharide hyaluronic acidmucopolysaccharide hyaluronic acid



Ocular EmbryologyOcular Embryology



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Orbital Anatomy

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