DR. PRATEEK VISHWAKARMADNB OPHTHALMOLOGY

BLOOD SUPPLY OF VISUAL PATHWAY

Introduction

Arteries of Brain : Circle of willis

Circle of willis : Lies in interpeduncular fossa

at the base of brain.

Encircles the pituitary stalk

provides important communications between theblood supply of the forebrain and hindbrain 

Formed by:Anterior communicating artAnt cerebral artPost communicating artPost cerebral artBasilar art

Basically a free anastomosis bertween 2 ICA and 2 VA

Vertebral Artery

Enter post cranial fossa through foramen magnum

Ascends upward, forward and medially on medulla oblongata

unite at lower border of pons to form BASILAR Artery.

Br. Of Cranial part of Vertebral artery:

1. Meningeal br2. Post spinal art3. Ant Spinal art4. Post inferior cerebellar art5. Medullary art

Basilar Artery

Ascends in groove on anterior surface of pons and at upper border divides into two PCA.

Br. Of Basilar art:1. Ant Inf cerebellar art2. Sup cerebellar art3. Labyrinthine art4. Pontine art5. Posterior Cerebral Art:

Posterior Cerebral Art

1.visual cortex2.posteromedial aspect of LGB3.post region of optic radiation

Calcarine artery: whole of Visual cortex and posterior portion of Optic Radiations

Posterior choroidal artery: post medial aspect of LGBPosterior choroidal artery

Internal carotid artery

1. Cervical 2. Petrous, 3. Cavernous and 4. Cerebral part

Internal carotid artery

Enters middle cranial fossa through carotid canal

Passes through foramen lacerumRuns in cavernous sinusEmerge from anterior part of its

roofLies lateral to OC

Cerebral Part: (Mn: CAMP Off)

Ophthalmic art

Choridal art: chaisma, optic tract (post aspect), LGB (ant and lateral aspect) and commencement of optic radiations.

Ant Cerebral: upper aspect of chiasma, intra cranial part of optic nerve.

Middle Cerebral: largest branchsuperolateral aspect of cerebrum, inferolateral aspect of chiasma, optic radiation, small part of visual cortex

Post Communicating Art: joins Post Cerebral art to form part of C.O.W.

Ophthalmic Artery

Br of ICA (after it leaves the roof of cavernous sinus)

At origin: inf to ON

Pass through the Optic canal within dural sheath of ON

At the apex of Orbit: lateral to ON and medial to occulomotor and abducent nerve and

Runs forward and upwards over Optic nerve ,below Superior rectus and then comesto lie medial to ON

Ends by dividing into:dorsal nasal artsupra trochleaar art

The ophthalmic artery and its branches are tortuous to accommodate for the movements of the eyeball.

Branches of Ophthalmic Artery:1. Central retinal art2. Long and Short posterior Ciliary art3. Muscular art: Ant ciliary art4. Lacrimal art: Lateral palpebral art5. Medial palpebral art6. Supra orbital art7. Anterior ethmoidal art8. Posterior ethmoidal art9. Recurrent meningeal art10. Dorsal nasal art (terminal br.)11. Supra trochlear art(terminal br.)

Long and Short Posterior Ciliary Artery

Two long post ciliary art : arise from ophthalmic art below ON

10-20 Short ciliary arteries: forms part of choroidal circulation

BLOOD SUPPLY OF VISUAL PATHWAY

Blood Supply Of Retina Outer four layers: Choriocapillaris

Inner six layers: Central retinal artery

Outer plexiform layer: Watershed areaIt gets blood supply from both, the central retinal artery and choriocapillaris.

Central Retinal Artery

In the optic nerve head: Superficial in the nasal part of

the cup

Covered by a thin layer of glial tissue (meniscus of Kuhnt, which separates the vessels from the vitreous)

Divides into superior and inferior branches

at disc margin: sup and inf br. Divide into nasal and temporal br.

In the retina: The four terminal branches divide dichotomously and end without anastomosis

One of the capillary plexuses is in the superficial zone (nerve fibre layer)and the other one is at the junction of inner nuclear and outer plexiform layer.

Macula

Superior and inferior temporal branches of central retinal artery

Cilioretinal artery: It is seen in some individuals. It is a branch of ciliary system of vessels.

Supplies macula It helps to retain the central vision

in the event of CRAO. Fovea: Avascular area (500 µm) Mainly supplied by choriocapillaris

CRAO

Nearly always at the lamina cribrosa

Generally, due to an embolus, there may be associated arteriosclerosis, hypertension or Buerger disease

Sudden and complete blindness, opaque and milky white retina, cherry red reflex at the fovea

Venous drainage of retina

Central retinal vein and its branches follows same pattern as CRA

Empties into sup and inf ophthalmic veins

Which drains into Cavernous sinus

CRVO

Presentation : sudden, u/l blurred vision.Fundus: tortuosity and dilatation of all

branches

with Dot/blot and flame shapedhemorrhages in all 4 quad mostnumerous at periphery

cotton wool spots ,

macular edema

Blood Supply Of The Optic Nerve

Differ significantly depending upon which segment is considered

Intraocular

Intraorbital

Intracanalicular

Intracranial

Intraocular (ONH)

Venous drainage of ONH- central retinal venous system

AION

Defect in the blood supply of anterior part of the optic nerve by posterior ciliary artery - AION

It produces a postlaminar infarct.

Can be inflammatory (arteritic) or Non-inflammatory (non arteritic)

Intraorbital

Intraorbital optic nerve is 3cm long while the entry of the central retinal artery is 5-15.5mm behind the globe.

So, the optic nerve here, is divided into two segments, proximal and distal.

Distal segment: Axial supply, in addition

Proximal segment: Centripetal branches of pial networkformed from br. Of PCAs

Periaxial system of vessels:1. Ophthalmic artery2. Long posterior ciliary arteries3. Short posterior ciliary arteries4. Lacrimal artery5. Central retinal artery6. Circle of Zinn

Axial system of vessels:1. Intraneural branches of central retinal artery2. Central collateral arteries from central retinal artery

PION

Disorders affecting small pial vessels supplying the intraorbital part of the optic nerve

Vision loss with afferent pupillary defect.

No visible ophthalmoscopic abnormality

It can occur in disorders with vasculitis and conditions producing acute systemic hypotension.

Intracanalicular

Lies in a watershed zone

Anteriorly from collateral br of Ophthalmic art

Posteriorly from pial vessels from -ICA and -Superior hypophyseal arteries.

As opposed to Intraorbital part of ON, which moves freely as the eye moves, the intra canalicular part is tightly fixed to optic canal, making it vulnerable to shearing injury in # skull

Intracranial

Exclusively supplied by the periaxial system of vessels

Pial plexus:1. Direct branches of internal carotid artery OR Recurrent branch of anterior superior hypophyseal artery: They supply to the inferior aspect of the optic nerve.

2. Branches from anterior cerebral artery: They supply to the superior aspect of the optic nerve

3. Recurrent branches from the ophthalmic artery

4. Twigs from the anterior communicating artery

Venous drainage of optic nerve

central retinal vein (primarily) and pial plexus of veins

ophthalmic vein.

The intracranial part is drained by anterior cerebral and basal veins.

Optic chiasma

Mainly derieved from br of Ant cerebral and Internal carotid art.

Superiorly: Anterior cerebral and anterior communicating arteries

Inferiorly: Internal carotid artery, anterior superior hypophyseal artery and posterior communicating artery

A branch of the ophthalmic artery supplies the antero-inferior margin of the chiasma.

Venous drainage

Superior chiasma › Anterior cerebral vein

Inferior aspect of chiasma › Basal vein

Optic tract

Optic tract

Venous drainage: Anterior cerebral vein and basal vein

Lateral geniculate body

Post Choroidal art

Occlusion of Anterior choroidal artery produces produces an upper- and lower-sector field defect.

Occlusion of Posterior choroidal art produces a homonymous horizontal sectoranopia

Optic radiations

Anterior part of optic radiations

Middle part of optic radiation

Perforating br. Of MCA

Posterior part of optic radiations

Venous drainage: Basal vein and middle cerebral vein

Visual cortex

calcarine branches of PCA

Anterior end of the calcarine sulcus: Middle cerebral artery

At the occipital pole of the cortex, there is an anastomosis between posterior and middle cerebral arteries. Therefore, in thrombosis of posterior cerebral artery, macula is spared.

Internal occipital vein › Great cerebral vein of Galen & straight sinus

Inferior cerebral vein › Cavernous sinus

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