Blood supply of the eye

Dr. Amer A. Shamsulddin

Arterial blood supply:

• Internal carotid artery:

• External carotid artery:

Note:

(eyelids and conjunctiva from both internal and external carotid arteries)

Internal carotid artery:

• First intracranial branch of the internal carotid justas the artery exits from the cavernous sinus

• optic foramen below and lateral to the optic nerve

• Pass over the optic nerve to its medial side

• Between the MR and SO

• Terminates by dividing into dorsonasal andsupratrochlear

Ophthalmic artery:

Branches of ophthalmic artery:• Central retinal a.

• Supra-orbital artery

• Posterior ciliary artery– Long posterior ciliary a. (2 arteries)

– Short post. Ciliary a. (10-20 arteries)

• Muscular arteries – Anterior ciliary a. (7 arteries)

• Lacrimal artery (terminate into zygomatic branches)

• Ant. And post. Ethmoidal arteries

• Superior and inferior palpebral arteries

• Dorsonasal artery

• Supratrochlear artery

Central retinal artery

• pierces the dural sheath of the opticn. 12 mm behind the globe

• It gives off small meningeal branchesto supply the pial sheath of the opticnerve.

• It’s functionally as end artery.

1. ophthalmic artery.2. central retinal artery3. ciliary arteries (on each side of the

optic nerve). These vessels divideinto 2 long posterior ciliaryarteries(#4 in Figure) and ~20 shortposterior ciliary arteries (#5 inFigure) that enter the eyeimmediately adjacent and around theoptic nerve . The short posteriorciliary arteries directly supply thechoroid and the long posterior ciliaryarteries travel in the suprachoroidalspace anteriorly (#6 in Figure) thensupply the choroid anteriorly viarecurrent branches.

posterior (#7 in Figure) and anterior (#8in Figure) ethmoidal vessels.

The superior oblique muscle is shown fororientation ( #9 in Figure).

Ciliary arteries• Long post, short post. And ant. ciliary aa. are the major blood supply to the

globe

• Long post. Ciliary aa:

– Paired arteries that pierce the sclera outside the circle of Zinn snd

– travel forward in the suprachoroidal space to the ciliary body,

– Gives recurrent branches that supply the choroid anterior to the equator and anastomose with short post ciliary aa.

• Short post. Ciliary aa:

– 10- 20 branches pierces the sclera around the optic n

– This anastomotic circle of Zinn supplies the optic n. head (optic disc)

– Supplies the choroid to the equator

• Ant. Ciliary aa:

– 7 arteries 2 for each rectus m. exept LR m. only 1

– Supply the sclera and conjunctiva and the iris

External carotid artery:

• External maxillary artery (facial artery)

– Angular artery

• Superficial temporal artery

• Internal maxillary artery

– Middle meningeal artery

Blood supply of the eyelids• The main arterial blood

supply:– Lat. Palpebral a. (from

lacrimal artery)– med. Palpebral a. ( from

ophthalmic artery)

• These palpebral aa. (frominternal carotid a.)anastamose with facial artery(external carotid) and itsbranch (zygomatico-temporal a.and angular a.) at the lat.aspect of the lid and form theMarginal and peripheralpalpebral arcades

Venous drainage:

• Medially: to ophthalmic and angular vv.

• Latrally: to superficial temporal v.

Lymph drainage

• Lat. 2/3 of upper and lower lidssuperficail parotid nodes (pre-auricular nn.)

• Medial submandibularnodes

Nerve supply:

• Lower lid:– infra-orbital (from V2)

– Med. Aspect infra-trochlear n. (V1)

• Upper lid: – Supra-orbital n.

– Supra-trochlear n.

– Lacrimal n. (v1)

Blood supply to the conjunctiva

• Palpebral conjunctivamarginal and peripheral arcades (from med. And lat. Palpebral aa.)

• Limbal conjunctiva ant. ciliary art.

• Venous drainage:The conj. veins sup. and inf. ophthalmic vv.

• Nerve supply: Bulbar conj. long ciliary nn. (nasocialiary of ophth. n.)

Blood supply of the ACLong post. ciliary aa. anastomose with ant. ciliary aa.

– Major arterial arcade (ciliary stroma)

– Minor arterial arcade (At the collarete of the iris)

• They are the major blood supply to the iris and ciliary body

• Iridial vessels are non-fenestrated (endothilial tight junctions)

• Vessels in the ciliary body are fenestrated and no tight junctions

• Blood-aqueous barrier tight junctions in the ciliary epithelium

• Venous drainage: follow the aa. minor venous circle directly into the vortex veins (not into the corresponding major circle)

retinal blood supply:

• The outer plexiform layer isthe watershed region

• Outer to this layer(neuroreceptors and RPE) choroidal circulation bydiffusion

• Inner 2/3 central retinala. directly

• Retinal aa. run in the nervefiber layer with 4 branchesfor each quadrant

• Retinal capillaries are concentrated in the maculabut are absent from the fovea centralis (FAZ)

• In 20% of people there’s cilioretinal a. (from post.

ciliary a.) supplies the macula

Blood retinal barrier• Inner BRB:

– Tight junctions between the endothelial cells or retinal blood vessels

• Outer BRB:

– Tight junctions between

RPE cells

Blood supply to the visual pathway

• Intra-ocular optic n. short post. ciliary aa. That form the circle of Zinn.

• The central retinal a. pierces the dural sheaths of the orbital optic n. but doest supply it, it’s supplied by pial plexus of vessels

• Intracraneal optic n. is supplied by the superior hypophyseal and ophthalmic aa.

• A rise in the ICP may compromise blood flow to these vessels papilloedema

• Optic tracts pial arteries (from ant.Choroidal and post. Communicating aa)

• Lat. Geniculate body and post. aspect ofoptic radiations the middle cerebral a. withthe post. Cerebral a.

• Visual cortex:

– Most of its blood supply post. Cerebral a.

– Occipital pole (macular area)Middle cerebral a.(causing macular sparing in some of occipital lobestrokes)

Venous drainage of the eye

• There 4 vortex veins

(2 on each side)

exit the eyeball

post. to the equator.

• Sup. Vortex vv. and central retinal v. Superiorophthalmic v. (which is from supra-orbital and facial vv.)

• Inferior vortex vv. Inf. Ophthalmic v. which:

– may drain to the sup. Ophthalmic v or directly tocavernous sinus

– communicates with the pterygoid venous plexus (andbecause of the reason the inf. From this plexus may reachcavernous sinus cavernous sinus thrombosis)

Cavernous sinus• Extends from the sup. orbital fissure ant.ly to

the apex of petrous bone (temporal bone)

• Floor dural coverings of greater wing of sphenoid

• Med body of sphenoid and pitiutary fossa

• Internal carotid a. grooving the medial wall of the sinus then pierces its roof.

• The abducent nerve (VI) travels within it

(first nerve to damage by cavernous

sinus thrombosis)

• Its lat. Wall encloses III, IV, V1 & V2 nerves.