Blood supply of the eye

ophthalmology

1. Blood supply of the eye Dr. Amer A. Shamsulddin

2. Arterial blood supply: Internal carotid artery: External carotid artery: Note: ( eyelids and conjunctiva from both internal and external carotid arteries)

3. Internal carotid artery: First intracranial branch of the internal carotid just as 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 and supratrochlear Ophthalmic artery:

4. 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

5. Central retinal artery pierces the dural sheath of the optic n. 12 mm behind the globe It gives off small meningeal branches to supply the pial sheath of the optic nerve. It’s functionally as end artery.

6. ophthalmic artery. central retinal artery ciliary arteries (on each side of the optic nerve). These vessels divide into 2 long posterior ciliary arteries (#4 in Figure) and ~20 short posterior ciliary arteries (#5 in Figure) that enter the eye immediately adjacent and around the optic nerve . The short posterior ciliary arteries directly supply the choroid and the long posterior ciliary arteries travel in the suprachoroidal space anteriorly (#6 in Figure) then supply the choroid anteriorly via recurrent branches. posterior (#7 in Figure) and anterior (#8 in Figure) ethmoidal vessels . The superior oblique muscle is shown for orientation ( #9 in Figure).

7. 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

8. External carotid artery: External maxillary artery (facial artery) Angular artery Superficial temporal artery Internal maxillary artery Middle meningeal artery

9. 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 . (from internal carotid a.) anastamose with facial artery (external carotid) and its branch ( zygomatico -temporal a. and angular a. ) at the lat. aspect of the lid and form the Marginal and peripheral palpebral arcades

10. Venous drainage: Medially: to ophthalmic and angular vv. Latrally : to superficial temporal v.

11. Lymph drainage Lat. 2/3 of upper and lower lids  superficail parotid nodes ( pre-auricular nn . ) Medial  submandibular nodes

12. 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)

13. Blood supply to the conjunctiva Palpebral conjunctiva  marginal 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.)

14. Blood supply of the AC Long 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)

15. retinal blood supply: The outer plexiform layer is the watershed region Outer to this layer ( neuroreceptors and RPE)  choroidal circulation by diffusion Inner 2/3  central retinal a . directly Retinal aa . run in the nerve fiber layer with 4 branches for each quadrant

16. Retinal capillaries are concentrated in the macula but are absent from the fovea centralis (FAZ) In 20% of people there’s cilioretinal a. (from post. ciliary a.) supplies the macula

17. Blood retinal barrier Inner BRB: Tight junctions between the endothelial cells or retinal blood vessels Outer BRB: Tight junctions between RPE cells

18. 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

19. Optic tracts  pial arteries (from ant. Choroidal and post. Communicating aa ) Lat. Geniculate body and post. aspect of optic radiations  the middle cerebral a . with the 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 lobe strokes)

20. Venous drainage of the eye

21. There 4 vortex veins (2 on each side) exit the eyeball post. to the equator. Sup. Vortex vv. and central retinal v.  Superior ophthalmic 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 to cavernous sinus communicates with the pterygoid venous plexus (and because of the reason the inf. From this plexus may reach cavernous sinus  cavernous sinus thrombosis)

22. 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

23. 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.