Orbital vasculature Flashcards
What is the origin of the ophthalmic artery?
C6 segment of ICA
Within cavernous sinus
Can also arise from C4 or C5 segment. Can also arise from MMA, ACA, ICA bifurcation and basilar artery.
What is the course of the ophthalmic artery?
Initially lies within dural arachnoid sheath of optic nerve
Then pierces sheath on exiting optic canal, runs inferolaterally along optic nerve, then crosses superomedially (inferomedially in 15% of pop) along optic nerve accompanied by nasociliary nerve
Which muscles does the ophthalmic artery lie between?
Superior oblique and medial rectus
What are the terminal branches of the ophthalmic artery?
Supratrochlear artery and dorsal nasal artery
What are the branches of the ophthalmic artery?
Central retinal artery Muscular branches (sup + inf) Posterior ciliary arteries Lacrimal artery Supraorbital artery Posterior ethmoidal artery Anterior ethmoidal artery Medial palpebral arteries
Supratrochlear artery} Terminal branches
Dorsal nasal artery}
How do ophthalmic artery aneurysms present?
Subarachnoid haemorrhage and visual defecits
Incidental diagnosis 35%
Describe the course of the central retinal artery
First branch of ophthalmic artery
Starts about 1.25cm behind the eyeball
Pierces dural sheath and passes across subarachnoid space to enter the centre of the optic nerve
Runs with retinal vein and pierces lamina cribosa to enter eyeball
What is a key anatomical variant which improves outcomes in central retinal artery occlusion?
Presence of cilioretinal artery
Describe the lacrimal artery
2nd branch of ophthalmic artery Runs above lateral rectus Accompanied by lacrimal nerve Supplies lacrimal gland and eyelids Gives rise to lateral palpebral arteries( anastomose and form superior and inferior palpebral arches and anastomses with external carotid artery vis transverse facial artery) and zygomaticofacial and zgyomaticotemporal arteries
Where do the anterior ciliary arteries originate?
Muscular branch arteries to rectus muscles
What is the origin of the long and short ciliary arteries?
Posterior ciliary arteries from ophthalmic arteries
Forms major arterial circle of the iris
Describe the course of the supraorbital artery
Arises from ophthalmic artery as it crosses optic nerve
Passes superiorly around superior rectus and LPS
Exits orbit via supraorbital notch
Supplies LPS, frontal sinus, upper eyelid, skin of scalp and forehead
gives off posterior and anterior ethmoidal arteries
Where do the medial palpebral arteries arise from?
Inferior part of ophthalmic artery below the SO pulley
Travel behind lacrimal sac and form palpebral arches which supply eyelids and conjunctiva
Describe the course of the dorsal nasal artery
One of the terminal branches of the ophthalmic artery
Descends down the side of the nose, gives branches to the lacrimal sac and anastomses to the facial artery
Describe the course of the supratrochlear artery
Leaves orbit via orbital septum above SO pullery accompanied by supratrochlear nerve
Supplies skin of forehead and skull
What is the drainage of the orbit?
Superior ophthalmic vein
Vortex veins
Drains into cavernous sinus
Communicates with arterial system posteriorly to the orbit, and anteriorly around rim of optic cup
How does the ophthalmic artery develop?
First portion arises from hyaloid artery
Second portion arises from stapedial artery
Which other artery (besides ophthalmic) may be the main orbital artery in some cases?
Middle meningeal artery
What are the 3 portions of the ophthalmic artery
Intracranial (internal carotid artery)
Intracanalicular (optic canal)
Intraorbital (annulus of zinn to intraconal space)
Does the orbital portion of the ophthalmic artery run over or under the optic nerve?
Medially over (81%) or under (19%)
Where does the recurrent meningeal artery run?
Passes through superior orbital fissure
What does the superior muscular artery supply?
SR LR LPS and SO
What does the inferior muscular artery supply?
IR, MR and IO
Which ethmoidal artery is bigger?
Anterior ethmoidal artery Passes through anterior ethmoidal canal to reach anterior cranial fossa
Describe the course of the infraorbital artery
Arises from maxillary artery (external carotid) in the pterygopalatine fossa and enters orbit via inferior orbital fissure
Supplies inferior orbit, branches to IR and IO, lacrimal sac and gland and soft tissues of orbital floor
What is the clinical relevance of angular vein?
Descends across anterior limb of medial canthal tendon so is at risk during DCR
Continuous with facial vein
What is the clinical relevance of the facial vein
Vein has no valves
Communicates with pterygoid venous plexus and cavernous sinus so sepsis may spread from face to meninges
Where does the superior ophthalmic vein run?
Accompanies ophthalmic artery between the optic nerve and SR through superior orbital fissure to cavernous sinus
Drains inferior ophthalmic and middle ophthalmic veins plus 2 vortex veins, muscular, ethmoidal and palpebral veins
What is the difference between the middle ophthalmic vein and medial ophthalmic vein?
Middle: present in 1-20% of orbits.Runs with inferior ophthalmic vein
Medial: present in 40% of orbits
What are the key features of the cavernous sinus
3cm long, 1cm high 0.5cm wide
Contains ICA, abducens nerve and sympathetic plexus
Transversed by 3rd 4th and 5th cranial nerves in the lateral wall
Drained by the superior and inferior sinuses and emissary veins
What is the lymph drainge of the eyelids?
lat 2/3 upper eyelid, lat 1/3 lower eyelid and lat 1/2 conjunctiva =preauricular
med 1/3 upper eyelid,med 2/3 lower eyelid and med 1/2 conjunctiva = submandibular nodes
What is the lymphatics of the orbit?
Absent
Excess fluid appears to pass posteriorly
Where does the inferior ophthalmic vein run?
Arises anteriorly on the floor of the orbit from inferior venous network within the muscle cone. Runs backwards on inferior rectus and drains into cavernous sinus. Receives inferior 2 vortex veins
What do the superior and inferior roots of the superior ophthalmic vein connect to?
superior root: supraorbital vein
inferior root: angular vein
