orbital blood supply

Orbital Blood Supply

Othman Al-Abbadi, M.D

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Ophthalmic artery

The first main branch of the internal carotid

artery.

Course:

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Relation to the optic

nerve

Relation to the

meninges

Pre-optic canal Inferolateral Subarachnoid

Optic canal Inferolateral Dural-Arachnoid sheath

Orbital cavity Lateral Extra-dural

Superior 85%

Inferior 15%

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Branches

1. Central artery of the retina2. Lacrimal artery3. Muscular branches4. Ciliary arteries5. Supraorbital artery6. Posterior ethmoidal artery7. Anterior ethmoidal artery8. Meningeal artery9. Medial palpebral arteries10. Supratrochlear arteries11. Dorsal nasal artery

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Central retinal artery

First branch from the ophthalmic artery.

End arteries.

Course:

◦ Runs beneath optic nerve, then at about 1.25cm behind eyeball it pierces the dural & arachnoid sheaths of optic n, enters eyeball through lamina cribrosa

Divides into equal superior & inferior branches, then another division (nasal & temporal).

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Branches:◦ Small meningeal branches supply the pial

sheath

◦ Central collateral branches which pass with the CRA to the lamina cribrosa & a branch goes posteiorly to supply the macular nerve fibers

Circle of Zinn occurs between the pialvessels & the small vessels in the sclera around the nerve head.

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Lacrimal artery

Runs on upper border of the LR, passes through lacrimal gland & sends terminal branches to the eyelids & conjunctiva.

Branches: ◦ Lateral palpebral to the U & L eyelids &

anastomose with the medial palpebral

◦ Zygomatic which pass through the zygomaticofacial & zygomaticotemporalforaminae

◦ Muscular branch to the LR

◦ Recurrent meningeal anastomoses with the middle meningeal artery.

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Muscular branches

Most of these branches accompany

the branches of the oculomotor nerve.

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Ciliary arteries

1. Long posterior ciliary artery

◦ 2 in no.

◦ Pierce the sclera & run in the epichoroidal space

to the ciliary body where they divide into upper &

lower branches & encircle iris

◦ Anastomose with the anterior ciliary arteries to

form the major arterial circle of iris..

◦ recurrent branches supply the choroid posteriorly to

the equator & anastomose with the short posterior

ciliary arteries

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2. Short posterior ciliary arteries:

◦ 7 in no.

◦ divide into 10-20 branches

◦ run around the optic nerve before piercing the sclera to

supply the choroid as far as the equator where they

anastomose with recurrent branches of the LPCA, ACA &

the major arterial circle of the iris

A number of small branches form an anastomotic

ring(ring of Zinn) around optic disc with the pial

arteries

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Cilioretinal artery

◦ ~15-20% of the population

◦ Enters the retina at the lateral border of the

optic nerve & supplies the retina between the

disc & the macula

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3. Anterior ciliary arteries

◦ 7 in no.

◦ originate from the muscular branches

◦ Join the LPCA to form the major arterial

circle of iris.

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Supraorbital artery

Runs at the medial border of the SR & LPS then

with the supraorbital nerve between the LPS &

orbital roof,

leaves orbit through the supraorbital foramen &

ascends to the scalp deep to the frontalis

Anastomose with supratrochlear & superficial

temporal arteries

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Posterior ethmoidal artery

Passes between the upper border of the MR &

SO muscles to enter the posterior ethmoidal

canal

Supplies posterior ethmoidal air sinuses, dura of

anterior cranial fossa & upper part of nasal

mucosa.

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Anterior ethmoidal artery

Larger

Enters anterior ethmoidal canal then

anterior cranial fossa & passes into the

nose through cribriform plate down in a

groove in the nasal bone to enter face

between the nasal bone & upper cartilage

supplies ant. & middle ethmoidal air cells,

frontal air sinus, meninges, ant. nasal

mucosa & skin of nose.

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Meningeal artery

Runs posteriorly through the superior

orbital fissure to supply meninges of

middle cranial fossa.

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Medial palbebral atery

Arise below the pulley for the SO

Descend behind the lacrimal sac

pierce the orbital septum above & below the

medial palpebral ligament

form peripheral & marginal arterial arches

Run between the orbicularis oculi & the tarsal

plate

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Supratrochlear artery

Terminal branch

Pierces the orbital septum above pulley for the

SO

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Dorsal nasal artery

Terminal branch

Pierces the orbital septum

Passes above medial palpebral ligament &

descends to nose, gives branches to lacrimal sac

& anastomoses with the facial artery

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Arterial Supply of Eyeball

Outer 1/3rd (up to the outer nuclear layer)

is avascular & supplied by the choroidal

vessels

Inner 2/3rd by the CRA

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Veins of the Orbit

Tortuous & freely anastomose with one

another

No valves

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Superior ophthalmic vein

Larger

formed by union of supraorbital & facial

veins

communicates with CRV, then recieves

IOV & 2 vorticose veins from the upper

part of the eyeball

Leaves the orbit through superior orbital

fissure to join the cavernous sinus.

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Inferior Ophthalmic vein

Arises from venous plexus in orbital floor,

Communicates with facial v & pterygoid venous

plexus,

Receives muscular branches & 2 inferior

vorticose v,

Drains into the cavernous sinus or the pterygoid

venous plexus.

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Central retinal vein

Leaves the eyeball by piercing lamina cribrosa

with the CRA

Drains into cavernous sinus or SOV.

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