ORBIT IIORBIT II

Dr. Mujahid KhanDr. Mujahid Khan

Blood SupplyBlood Supply

Ophthalmic Artery: Ophthalmic Artery:

• It is a branch of Internal Carotid ArteryIt is a branch of Internal Carotid Artery

• Emerges from cavernous sinusEmerges from cavernous sinus

• Runs forward lateral to the optic nerveRuns forward lateral to the optic nerve

• Reaches the medial wall of the orbitReaches the medial wall of the orbit

• Gives away several branches Gives away several branches

Central Artery of RetinaCentral Artery of Retina

• Is a small branchIs a small branch

• Pierces the meningeal sheath of optic Pierces the meningeal sheath of optic nerve & gain entrance to the nervenerve & gain entrance to the nerve

• Enters the eyeball at the centre of optic Enters the eyeball at the centre of optic discdisc

• Divides into 2 branches called end arteriesDivides into 2 branches called end arteries

Ciliary ArteriesCiliary Arteries

• Can be divided in two groupsCan be divided in two groups

• Anterior group enters the eyeball near the Anterior group enters the eyeball near the corneoscleral junctioncorneoscleral junction

• Posterior group enters the eyeball near the Posterior group enters the eyeball near the optic nerveoptic nerve

Lacrimal ArteryLacrimal Artery

• It supplies the lacrimal glandIt supplies the lacrimal gland

Supratrochlear & Supra orbital Supratrochlear & Supra orbital ArteriesArteries

• Are distributed to the skin of the foreheadAre distributed to the skin of the forehead

Ophthalmic VeinsOphthalmic Veins• Superior ophtalmic vein communicates in Superior ophtalmic vein communicates in

front with the facial veinfront with the facial vein

• Inferior ophthalmic vein communicates Inferior ophthalmic vein communicates with the pterygoid plexus through the with the pterygoid plexus through the inferior orbital fissureinferior orbital fissure

• Both the veins pass backward through Both the veins pass backward through superior orbital fissure & drain into superior orbital fissure & drain into cavernous sinuscavernous sinus

Lymph vesselsLymph vessels

• No lymph nodes or vessels are present in No lymph nodes or vessels are present in the orbital cavitythe orbital cavity

The EyeThe Eye

• Eyeball consists of 3 coats:Eyeball consists of 3 coats:

• The fibrous coatThe fibrous coat

• The vascular pigmented coatThe vascular pigmented coat

• The nervous coatThe nervous coat

Fibrous CoatFibrous Coat

• Made up of posterior opaque part, the Made up of posterior opaque part, the sclera & anterior tranparent part corneasclera & anterior tranparent part cornea

ScleraSclera• Composed of dense fibrous tissueComposed of dense fibrous tissue

• Pierced by optic nerve posteriorly and is fused Pierced by optic nerve posteriorly and is fused with the dural sheath of the nervewith the dural sheath of the nerve

• Lamina Cribrosa is the area of sclera that is Lamina Cribrosa is the area of sclera that is pierced by optic nerve fiberspierced by optic nerve fibers

• Also pierced by ciliary arteries & nervesAlso pierced by ciliary arteries & nerves

• Is continuous in front with the cornea Is continuous in front with the cornea

CorneaCornea

• Is transparentIs transparent

• Responsible for refraction of light entering Responsible for refraction of light entering the eyethe eye

• It is in contact with the aqueous humor It is in contact with the aqueous humor posteriorlyposteriorly

Vascular Pigmented CoatVascular Pigmented Coat

• Consists from behind forward:Consists from behind forward:

• ChoroidChoroid

• Ciliary bodyCiliary body

• IrisIris

ChoroidChoroid

• Is composed of an outer pigmented layer Is composed of an outer pigmented layer and an inner highly vascular layerand an inner highly vascular layer

Ciliary BodyCiliary Body

• Is continuous posteriorly with choroidIs continuous posteriorly with choroid• Anteriorly lies behind the peripheral Anteriorly lies behind the peripheral

margin of irismargin of iris

• Composed of:Composed of:

• Ciliary ring Ciliary ring • Ciliary process Ciliary process • Ciliary muscleCiliary muscle

• Ciliary ring is the posterior part of the Ciliary ring is the posterior part of the body, has shallow grooves, Ciliary striaebody, has shallow grooves, Ciliary striae

• Ciliary processes are radially arranged Ciliary processes are radially arranged folds connects the suspensory ligaments folds connects the suspensory ligaments of the lensof the lens

• Ciliary muscle is composed of meridianal Ciliary muscle is composed of meridianal and circular fibers of smooth musclesand circular fibers of smooth muscles

IrisIris

• Is a thin, contractile, pigmented diaphragmIs a thin, contractile, pigmented diaphragm

• Has central aperture called pupilHas central aperture called pupil

• Is suspended in the aqueous humor between Is suspended in the aqueous humor between the cornea and lensthe cornea and lens

• Its periphery is attached to the anterior surface Its periphery is attached to the anterior surface of the ciliary bodyof the ciliary body

• Divides the space between cornea and lens into Divides the space between cornea and lens into anterior & posterior chambersanterior & posterior chambers

Nervous Coat or RetinaNervous Coat or Retina• Consists of an outer pigmented layer & inner Consists of an outer pigmented layer & inner

nervous layernervous layer

• Its outer surface is in contact with choroidIts outer surface is in contact with choroid

• Inner layer in contact with the vitreous bodyInner layer in contact with the vitreous body

• Posterior three-fourths is the receptor organPosterior three-fourths is the receptor organ

• Macula lutea is the oval yellowish area in the Macula lutea is the oval yellowish area in the center of the posterior partcenter of the posterior part

• Fovea centralis is the central depressionFovea centralis is the central depression

RetinaRetina• Optic nerve leaves the retina to medial Optic nerve leaves the retina to medial

side of macula lutea by the optic discside of macula lutea by the optic disc

• Optic disc is depressed at its center, Optic disc is depressed at its center, where it is pierced by central arterywhere it is pierced by central artery

• Optic disc is insensitive to light and Optic disc is insensitive to light and referred as blind spotreferred as blind spot

• Optic disc is seen to be pale pink with Optic disc is seen to be pale pink with ophthalmoscope examinationophthalmoscope examination

Optic NerveOptic Nerve

• Enters the orbit from middle cranial fossa Enters the orbit from middle cranial fossa by passing through the optic canalby passing through the optic canal

• Accompanied by ophthalmic arteryAccompanied by ophthalmic artery

• It is surrounded by sheaths of pia, It is surrounded by sheaths of pia, arachnoid and dura matersarachnoid and dura maters

• It runs forward and laterally within the It runs forward and laterally within the cone of the recti muscles cone of the recti muscles

Optic NerveOptic Nerve

• Pierces the sclera at a point medial to the Pierces the sclera at a point medial to the posterior poleposterior pole

• The meninges fuse with the scleraThe meninges fuse with the sclera

• The subarachnoid space extends forward as far The subarachnoid space extends forward as far as the eyeballas the eyeball

• A rise in pressure of the CSF within the cranial A rise in pressure of the CSF within the cranial cavity is transmitted to the back of the eyeballcavity is transmitted to the back of the eyeball

Nasociliary NerveNasociliary Nerve

• Arises from the ophthalmic division of the Arises from the ophthalmic division of the trigeminal nerve in the lateral wall of the trigeminal nerve in the lateral wall of the cavernous sinuscavernous sinus

• Enters the orbit through the lower part of the Enters the orbit through the lower part of the superior orbital fissuresuperior orbital fissure

• Crosses above the optic nerve with the Crosses above the optic nerve with the ophthalmic arteryophthalmic artery

• Ends by dividing into the anterior ethmoidal and Ends by dividing into the anterior ethmoidal and infratrochlear nervesinfratrochlear nerves

Branches of Nasociliary NerveBranches of Nasociliary Nerve

• Communicating branch to the ciliary ganglionCommunicating branch to the ciliary ganglion

• The long ciliary nerves (2-3 in number)The long ciliary nerves (2-3 in number)

• Posterior ethmoidal nervePosterior ethmoidal nerve

• Infratrochlear nerveInfratrochlear nerve

• Anterior ethmoidal nerveAnterior ethmoidal nerve

• External nasal nerveExternal nasal nerve

Ciliary GanglionCiliary Ganglion

• It is about the size of a pinheadIt is about the size of a pinhead

• It is a parasympathetic ganglionIt is a parasympathetic ganglion

• Situated in the posterior part of the orbit on the lateral Situated in the posterior part of the orbit on the lateral side of the optic nerveside of the optic nerve

• Receives its preganglionic parasympathetic fibers from Receives its preganglionic parasympathetic fibers from the oculomotor nerve via nerve to inferior obliquethe oculomotor nerve via nerve to inferior oblique

• The postganglionic fibers leave the ganglion in the short The postganglionic fibers leave the ganglion in the short ciliary nervesciliary nerves

Contents of the EyeballContents of the Eyeball

• Aqueous HumorAqueous Humor

• Vitreous bodyVitreous body

• lenslens

Aqueous HumorAqueous Humor• Clear fluid fills the ant. & post. ChambersClear fluid fills the ant. & post. Chambers

• Is a secretion from ciliary processesIs a secretion from ciliary processes

• Drained away through canal of ShlemmDrained away through canal of Shlemm

• Obstruction to its draining results in glaucomaObstruction to its draining results in glaucoma

• Glaucoma causes degenerative changes in Glaucoma causes degenerative changes in the retina the retina

Aqueous HumorAqueous Humor

• Supports the wall of the eyeballSupports the wall of the eyeball

• Maintains its optical shapeMaintains its optical shape

• Nourishes the cornea and lensNourishes the cornea and lens

• Removes the products of metabolismRemoves the products of metabolism

Vitreous BodyVitreous Body• Is a tranparent gelIs a tranparent gel

• Fills the eyeball behind the lensFills the eyeball behind the lens

• Hyaloid canal is a narrow channel runs through Hyaloid canal is a narrow channel runs through it extends from optic disc to posterior surface of it extends from optic disc to posterior surface of the lensthe lens

• Canal is filled with hyaloid artery in fetusCanal is filled with hyaloid artery in fetus

• Contribute in the magnifying power of eyeContribute in the magnifying power of eye

• Supports posterior surface of lensSupports posterior surface of lens

LensLens• Is a transparent, biconvex structureIs a transparent, biconvex structure

• Enclosed in a transparent capsuleEnclosed in a transparent capsule

• Situated behind the iris & in front of vitreousSituated behind the iris & in front of vitreous

• Encircled by ciliary processEncircled by ciliary process

• Assumes globular shape due to tense elastic Assumes globular shape due to tense elastic capsulecapsule

• Its circumference attached to the ciliary process Its circumference attached to the ciliary process by suspensory ligamentby suspensory ligament

LensLens• Suspensory ligament keeps the elastic Suspensory ligament keeps the elastic

lens flattenedlens flattened

• Ciliary muscle contracts to accommodate Ciliary muscle contracts to accommodate the eye for close objectsthe eye for close objects

• Lens becomes dense & less elastic in Lens becomes dense & less elastic in advance age resulting in presbyopiaadvance age resulting in presbyopia

• Glasses are used to overcome presbyopiaGlasses are used to overcome presbyopia