Transcript BLOOD SUPPLY OF EYE - Home

Dr Dipali Chavan
In human,the eyes have two separate
systems of blood vessels which differ
anatomically and physiologically.
These are:1.Retinal vessels: supplying retina
2.Uveal or ciliary vessels: rest of eye
Both the systems arise from ophthalmic
artery, br.of internal carotid artery.
Both the systems of vessels are derived from
PERIOCULAR MESENCHYME derived from
NEURAL CREST and associated paraxial
mesoderm.
Development of vasculature starts from a
very early period of 5wks and continues
even after birth.
 The orbital contents arc supplied chiefly by the
internal carotid artery via its ophthalmic branch and,
to a minor extent, by the external carotid artery via
the infraorbital artery
 Venous drainage is via the Ophthalmic veins and
tributaries, mainly into the cavernous sinus, but also
into the facial veins.
 ARTERIES-foll.ones
 Ophthtalmic artery
 Cerebral arteries
 Circle of willis
 External carotid artery
 VENOUS DRAINAGE- goes into
 Superior ophthalmic vein
 Inferior ophthalmic vein
 Middle ophthalmic vein
 Medial ophthalmic vein
 Angular vein
 Cavernous sinus
 The artery is described in
three parts:
 1. intracranial;
 2. intracanalicular;
 3. intraorbital.
 Ophthalmic artery
Main source for the ocular structures.
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Branch of ICA
Intracranial part : At its origin,is medial to ant. Clinoid
process and inf.to optic nerve.
 intracanalicular part: after its origin ,the ophthalmic artery
passes through the optic canal within the dural sheath of
optic nerve , lying inferior to it.
 Intraorbital part :At the apex of the orbit in the muscle
cone , the artery pierces the dural sheath of the optic nerve
and comes to lie lateral to the optic nerve and medial to the
Oculomotor and Abducent nerves. At this point ,ciliary
ganglion lies between the Ophthalmic artery and lateral
rectus muscle.
 Intraorbital part (CONTD):
Then the artery moves forwards and upwards and crosses
over the optic nerve and below the superior rectus
muscle and comes to lie on the medial side of optic
nerve. Here it is accompanied by the nasocilliary nerve
and the superior ophthalmic vein (in 10-15 % cases
artery passes below the optic nerve.)then it moves
forward between medial rectus and superior oblique
muscle towards the maxillary process of the frontal
bone. The terminal part of artery enters the peripheral
surgical space of the orbit . Ends at medial end of upper
eyelid by dividing into two terminal branches, namely
dorsal nasal artery and supratrochlear artery.
 The usual order of appearance of branches of this
artery is:
1. central retinal;
2. medial and lateral posterior ciliary;
3. lacrimal (and lateral palpebral);
4. recurrent meningeal;
5. muscular (and anterior ciliary);
6. posterior ethmoidal;
7. supraorbital;
8. anterior ethmoidal;
9. medial palpebral;
10. collaterals to optic nerve sheath;
11. periosteal;
12. dorsal nasal (terminal);
13. supratrochlear (terminal).
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CENTRAL RETINAL ARTERY:arises near the optic foramen and courses ahead with 5-6 right
angle bends as followsOutside optic nerve- it runs a wavy course forward, below the
optic nerve, but adherent to the dural sheath to about 1015mm behind the eyeball, where at a point along the
inferomedial aspect of nerve it bends upwards to pierces the
dura and arachnoid ,from both of which it receives covering.
In the subarachnoid space- it bends forwards and after a short
course it again bends upwards at nearly right angle &
invaginates the pia to reach the centre of the nerve. the
entering vessel is thus clothed by pia along with the pial
vessels. it is also surrounded by a sympathetic nerve plexus (N
of tiedemann).
 In the centre of optic nerve- the artery bends forwards and
then in company with the vein, which lies on its temporal
side, it passes anteriorly and pierces the lamina cribrosa to
appear inside the eye.
 In the optic nerve head- it lies superficially in the nasal part
of physiological cup, covered only by that layer of glial
tissue(connective tissue meniscus of kuhnt)which closes
the physiological cup. here it divides into two br-sup & inf
,each further subdivides into temporal and a nasal br at or
near the margin of the optic disc.
 In the retina- 4 terminal br of CRA namely, sup nasal, sup
temporal, inf nasal & inf temporal divide dichotomously as
they proceed towards the ora serrata, where they end
without anastomosis.
Abbreviations: A = arachnoid; C = choroid; CRA = central retinal artery; Col. Br. = Collateral branches; CRV = central
retinal vein; D = dura; LC = lamina cribrosa; NFL = surface nerve fiber layer of the disc; OD = optic disc; ON = optic
nerve; P = pia; PCA = posterior ciliary artery; PR and PLR = prelaminar region; R = retina; RA = retinal arteriole; S =
sclera; SAS = subarachnoid space.
 Recurrent meningeal artery :
This artery passes through the superior orbital fissure.
It anastomoses with the middle meningeal artery ,which
is a branch of external carotid artery .thus ,this
anastomoses is between the internal and external
carotid arteries.
 Long and short posterior cilliary arteries.
-These arteries arise from the Ophthalmic artery below the
optic nerve., later divide into
10-20 branches .
-These branches run forwards, surround the optic nerve and
pierce the eyeball close to it.
- Most branches, the short ciliary arteries, enter the choroid.
Two long posterior ciliary arteries pierce the sclera medial
and lateral to the nerve and pass between the sclera and
choroid to supply the ciliary body, anastomosing
with anterior ciliary arteries to form the circulus arteriosus
iridis major, supplying the iris.
 Muscular branches:
The muscular arteries are subdivided into three groups:
the superior artery, supplies the superior and lateral recti,
levator and superior oblique (Hayreh, 1962).
The inferior artery, present in 98% of specimens, is the largest
branch on the orbital floor, supplies the inferior and medial
recti, inferior oblique and sometimes the lateral rectus
(Hayreh, 1962).
A variable number of independent vessels arise from the main
artery and also from the lacrimal and supraorbital.
The muscular arteries of the recti run forward with in their
tendons and pierce the sclera to anastomose with posterior
ciliary arteries. Their anterior ciliary rami pass forward in the
episclera to supply the subconjunctival, marginal corneal and
perilimbal conjunctival networks
 Lacrimal artery:
At the upper border of lateral rectus it supply the lacrimal gland.
It traverses the gland and supplies the eyelids and the conjunctiva
through its lateral palpebral branches and forms superior and
inferior anastomotic arcades with the medial palpebral arteries
 Anterior cilliary arteries:
Branches of the muscular arteries.
Seven in number ,two of each from sup rectus, inferior rectus,medial
rectus ,one branch from the lateral rectus. These artery give off
ant.conj.art.just before piercing the sclera at about 4mm from the
limbus.
These anastomose with the long posterior ciliary arteries and
supply ciliary body and iris.
 supraorbital artery:
Passes through the supraorbital notch, supplies the upper eyelid and
scalp.
 ARTERIES OF BRAIN
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INTERNAL CAROTID ARTERYEnters the middle cranial fossa by passing through carotid canal.
It runs in the cavernous sinus and emerges in the anterior part of roof.
Lies lat.to optic chiasma and terminates by dividing into ant. & middle
cerebral art.
The internal carotid artery gives off caroticotympanic and pterygoid
branches in its petrous part and cavernous, hypophyseal and
meningeal branches in its cavernous part.
Has foll.branches of cerebral part-Ophth.art.,Post.comm.A,Choroidal
art.,ant. & middle cerebral art(largest branch).
VERTEBRAL ARTERYEnters the post.cranial fossa by passing through foramen magnum and
unite with each other at the lower border of pons to form basilar artery
which in turn ultimately divides into two post.cerebral arteries.
 CIRCLE OF WILLIS Lies in interpeduncular fossa at the base of brain.
 Formed by-ant.comm.artery,ant.cerebral artery
,ICA,post.cerebral artery,post.comm.art, and the
basilar art.
 Thus basically a free anastomoses between ICA &
Vertebral A.
 Equalizes pressure on
the arteries of two sides.
 EXTERNAL CAROTID ARTERY Branch of common carotid artery.
 Passes upwards through the tissues of neck.
 Major branches which supply ocular adnexa are-
-Superficial Temporal A,Maxillary A,angular art,
infraorbital art, Transverse Facial A, Zygomatic art.
 Superior ophthalmic vein(SOV):
 Starts by joining of its superior and inferior roots in the superomedial
part of ant.orbit.
 In the orbit,it accompanies ophthalmic artery and lies above the optic
nv.
 Joins IOV near the sup.orbital fissure and finally terminates in the
cavernous sinus.
 Tribu.are-angular v, supraorbital v, lacrimal v, Central Retinal V,
Inferior Ophthalmic V, ant.ciliary v and two upper vorticose veins.
 Inferior ophthalmic vein(IOV): commences from inferior venous
network near the ant. part of floor of orbit.
 Terminates in the cavernous sinus either directly or by joining SOV.
 Receives trib.from- LL,lower and lat.ocular ms, conjunctiva ,lac.sac, &
lower two vorticose veins.
 Middle ophthalmic vein:
 Arises near the inf.margin of lat.rectus ms.
 Drains the inf.venous network and ultimately joins the confluence of Sup.
Ophthalmic V in the cavernous sinus.
 Some considered it as 2nd Inf Ophthalmic V.
 Seen in about 20% of individuals.
 Medial ophthalmic vein:
 Arises either from the inf. root or from ant.part of the SOV.
 Ultimately drains into cavernous sinus.
 Present in about 40% of individuals.
 Angular vein:
 Formed by the union of supraorbital and supratrochlear v.
 Lies lat.to angular art. And is situ.8mm medial to medial canthus.
 Below continues as the facial vein.
 Imp.landmark during the lac.sac surgery.
 Trib.are-Supra Orbi.V,Supra Troch.V,,Sup. and inf. Superficial palpebral v, and
superficial nasal br.
 Cavernous sinus:
 It is a large venous space situ. in the middle cranial fossa, one on
either side of body of the sphenoid bone.
 Tributaries are SOV,IOV or its branch, medial oph. v, central retinal v., veins
from brain( sup middle cerebral vein ,inf cerebral vein) and from
the meninges (middle meningeal vein).
 Draining channels Transvrse s(through the sup petrosal sinus) , Internal jugular
V(inf petrosal sinus), pterygoid plexus of veins(through the
emissary v), and into the opp. sinus.
 As cavernous sinus communicates to SOV & IOV,so infections
from the areas drained by these veins can pass to cavernous sinus
and vice-versa.
 CHOROIDAL VESSELS Acc.to Hayreh, post.ciliary arteries,choriocapillaries as well
as the vortex veins have a segmental distribution in the
choroid. they are also more or less end arteries.
 Layers-3 stratified layers Outermost-large venules
 Middle-smaller venules and arterioles.
 Innermost-choriocapillarie
 CHOROIDAL ARTERIES Intima consists of endothelium,basement mb., and
int.elastic lamina.
 Media-single continuous layer of smooth ms.cells which
contains abundant myofilaments.
 Adventitia-collagen fibre bundles,scattered elastic fibres
and occasional fibroblasts.
 CHOROIDAL ARTERIOLES Foll.variations from arteries Internal elastic mb.absent
 Muscle layer becomes discontinuous and more
circumferentially arranged.
 Amt.of collagen in the adventitia is considearbly
diminished.
 CHOROIDAL VEINS AND VENULES Veins vary in dia.from 50-150u and consists of
endothelium, basement mb., one or two layers of smooth
muscles and a relatively thick collagenous adventitia.
 Venules are<40u.intima same as veins, but media contains
a discontinuous layer of longitudinally arranged pericytes.
 CHORIOCAPILLARIES Large dia.8-40u.
 Vessel wall consists of fenestrated endothelium,surr.by
a membrane.
fenestrations are 700-800A’ in dia. and are covered by a
diaphragm.
 Highly permeable to large molecules.so play an
imp.role in adequate supply of vit.A to the pigmented
epithelium of the retina.
 BLOOD VESSELS OF IRIS Arterial supply mainly from major arterial circle.radial
arteries which supply the iris are basically arterioles.
 Major charac. histo. feature is a well developed and
modified adventitia. innermost layer consists of
longitudinal loosely arranged collagen fibrils enmeshed in
an amorphous ground substance. outermost layer consists
of densely packed circular collagen fibres.
 Radial veins are technically pericytic venules(collecting
venules).
 Capillaries have a continuous non-fenestrated
endothelium.low permeability of iridial capillaries and
venules form a part of functional blood-aqueous barrier.
 Blood flow in retinal vessels is laminar with some
pulsatile component.
 Blood flow in iris vessels is also laminar.
 Blood flow in choroidal vessels is controversial owing to
cavernous structure of choriocapillaries-it is supposed that choroidal flow is mostly laminar with
geographical filling of the separate choroidal segments.
=retinal vsls receive about 5%of total ocular blood flow.
=choroid about 65 to 85%,iris & ciliary body about 10 to 35%
of ocular blood flow.
 Ocular blood flow is regulated by local as well as systemic
regulatory mechanisms.
 Main factors influencing it are:
-pressure head
-autoregulation
-resistance to the blood vessels
-viscocity of the blood
.main site of resistance is arterioles
.it is regulated by neural mechanisms and chemical mediators.
 Blood flow in choroid and retinal vessels is steady and not
alternating as the precapillary sphincters are absent here.
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PERFUSION PRESSURE :
(MAP-IOP)
-Either a fall in MAP or a rise in IOP should lower the PP and
thus also the blood flow.
- It mainly affects the blood flow in choroidal vessels not in
retinal or ciliary vessels (presence of autoregulation in
these vessels).
 AUTOREGULATION:it is a property of vascular bed that
permits nearly constant blood flow over a wide range of
perfusion pressure.
-retinal vessels exhibit such a phenomenon.
-two theories for this: a)myogenic theory
b)metabolic theory
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NERVOUS CONTROL: Influences only choroidal vs,not the retinal ones.
Effect of sympathetic supply: assists autoregulatory mech.& maintain the
intraocular blood flow and volume constant.both the ciliary as well as
extraocular part of CRA are under its control.
Effect of parasympathetic supply : exists in ciliary processes and the
choroid.These increase the blood flow when required by causing
vasodilatation in the whole uvea,most marked in the choroid.
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CHEMICAL CONTROL: HYPERCARBIA causes marked vasodilatation of the
uveal ts & increases the total blood volume in eye,resulting in rise in IOP.
While the inhalation of 100% o2 causes slight vasoconstriction of retinal
vs.inhalation of 7% co2 & 21% o2 cause moderate dilation of visible retinal
vessels.
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DRUGS: drugs like papaverine,caffeine causes vasodilatation while
ergotamine causes vasoconstriction,but NE increases blood flow inspite of
its vasoconstricting effect.
 From anterior to posterior diff.parts of eye areo Eye Abrows and the eyelids
o Cornea
o Conjuctiva
o Lacrimal glands and the lacrimal passages
o Extraocular muscles
o Sclera
o Uveal tissues
o Lens
o Vitreous
o Retina
o The visual pathway
 EYEBROWS:
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Arterial supply- derived from supraorbital and superficial
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temporal a.
Venous drainage:- supraorbital, frontal, angular and
superficial temporal veins.
EYELIDS:
Arterial supply:
Mainly supplied by medial and lateral palpebral A(the
branches of dorsal nasal and lacrimal art.)
The sup. And inf.art. enter the upper and lower eyelids by
piercing through septum orbitale above and below the medial
palpebral lig.,respectively.
Each medial palpebral A. then anastomoses with the
corresponding lat.palpebral a, to form marginal arterial
arcade,which lies in submuscular plane in front of tarsal plate
some 2-3mm away from lid margin,in each eyelid.
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In the upper eyelid,another arcade sup.or peripheral arterial arcade,is
formed from the sup.branches of med.palpebral a,which lies near the
upper border of tarsal plate.
Branches from the arterial arcades go forward to supply orbicularis and
skin & backward to supply tarsal glands & conjuctiva.
Venous drainage:
Veins are larger and more numerous than the arteries of the eyelids.
Arranged on two sets of venous plexus in each eyelid:
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Pretarsal ven.plexusDrains structures superficial to tarsus.
On medial side,drain into subcutaneous veins mainly the angular veinultimately drains into internal jugular vein.
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Post-tarsal ven.plexus:
Drains structures posterior to the tarsal plate.
Ultimately drains into the ophthalmic veins.
 CONJUCTIVA:
 Arterial supply-derived from three sources
 Marginal arcade of eyelid
 The peripheral arterial arcade
 The anterior ciliary arteries.
 palpebral conjuctiva and fornices are supplied by
br.from marginal and peripheral arcades of
eyelids.And the bulbar conj.is supplied by
post.conj.art.and ant.conj.art.
 Venous drainage:
 The veins from the conjuctiva drain into the venous
plexus of eyelids-drain into the sup.or the inferior
ophthalmic veins.
 A circumcorneal zone of veins about 5-6mm from the
limbus drain into the ant.ciliary veins.
 CORNEA:
 It is an avascular structure.
 Small twigs of vessels derived from the anterior ciliary
vessels invade its periphery for about 1mm and provide
nourishment.
 Actually these loops are not in the cornea,but in the
subconjuctival tissue which overlaps the cornea.
 Relative avascularity is responsible for its transparency.
 Progressive vascularization is a harmful process as it
interferes with its functional properties, especially its
transparency.
 LACRIMAL GLANDS AND THE LACRIMAL PASSAGES:
 LACRIMAL GLAND Arterial supply-
 Main lacrimal gland is supplied by lacrimal artery,a br.of ophthalmic artery.
 Sometimes a br.of transverse facial artery may also supply the gland.
 Venous drainage Gland is drained by lacrimal veins --the ophthalmic vein.
 LACRIMAL PASSAGES Arterial supply derived from superior and inferior palpebral art(br.of ophthalmic
artery),angular art,infraorbital artery and nasal br.of sphenopalatine artery.
 Venous drainage occurs into the angular vein and the infraorbital vein from above and into the
nasal vein from below.
 EXTRAOCULAR MUSCLE:
 Arterial supply Usually two branches of the ophthalmic artery,namely medial and
lateral muscular branches,supply the extra ocular ms.
 Medial ms br-larger of the two.
 Supplies the MR,IR and IO ms.
 Medial rectus also receives a br.from the lacrimal artery and the inferior
rectus and oblique ms receive br.from the infraorbital artery.
 Lateral ms br-supplies the LR,SR,SO and the LPS ms.
 These muscular branches give rise to anterior ciliary arteries.
 Venous drainage Veins from the EOM correspond to the arteries and empty into the
superior and inferior ophthalmic veins.
 SCLERA:
 Relatively avascular structure.
 However,anterior to insertion of the recti
muscles,anterior ciliary artery form a dense episcleral
plexus.
 Posterior part of the sclera receives small branch from
the long and short posterior ciliary arteries.
 UVEAL TISSUE:
 Arterial supply supplied by 3 sets of arteries-
 Short posterior ciliary arteries-
-arise as two trunks from ophthalmic artery.
-Each trunk further divides into 10-20 br.which pierce the sclera around the
optic nerve and supplied the choroid in the segmental manner.
 Long posterior ciliary arteries-
-2 in no.(nasal and temporal),pierce the sclera obliquely on medial and lateral
side of the optic nerve and run forward in the suprachoroidal space to reach
the ciliary muscle,without giving any branch.at the anterior end of ciliary
muscle.
-these anastomose with each other and with the anterior ciliary arteries to form
the major arterial circle and also give branches which supply the ciliary body.
 CONTD…
 Anterior ciliary arteries-
 deri.from muscular branches of ophthalmic artery.
-several branches arises from the circulus arteriosus
major plexus and supply the ciliary processes(one
br.for each process).
-similarly many br.from it run radially through the iris
towards pupillary margin where they anastomose with
each other to form circulus arteriosus minor.
 Venous drainage-
veins draining uveal blood are Anterior ciliary veins- these are tributaries of the muscular veins.
 Since they carry blood only from the ciliary muscle,they are
smaller than the corresponding arteries.
 Smaller veins from the sclera-these correspond to the scleral
branches of short ciliary arteries.they only carry blood from the
sclera and not from the choroid and are, therefore ,smaller than
the corresponding arteries.
 The venae verticosae(vortex veins or posterior ciliary veins)-Usually 4 in no.(sup & inf temporal,and sup & inf
nasal),pierces the sclera obliquely on each side of SR & IR,6mm
behind the equator of the globe.
-Of these STV is most posterior(8mm behind equator) and
ITV is the most anterior(5.5mm behind the equator.they have an
ampullary dilatation at their choroidal end.
 These veins drain blood from-
-whole of choroid,receive small veins from optic nerve
head,smtimes small v from retina.anterior tributaries come
from the iris,ciliary processes,ciliary muscle and ant.part of
choroid.
-there is no major venous circle corresponding to major
arterial circle.
-these all 4 veins converge towards the apex of orbit d/t
oblique arrangement of scleral canals.two sup.vortex veins
open into sup.ophthalmic v directly or through its
muscular or lacrimal tributaries.two inf.vortex veins open
into the inf.ophthalmic veins.
 BLOOD SUPPLY OF RETINA diff.parts are supplied by diff.arteries Outer 4 layers of the retina viz.RPE,layer of rods and cones , ELM
& ONL get their nutrition from choriocapillaries.
 Inner 6 layers ie OPL,INL,IPL,GCL,NFL & ILM get their supply
from central retinal artery.
 OPL gets its blood supply partly from CRA and partly from
choriocapillaries by diffusion.
 The fovea is an avascular area mainly supplied by
choriocapillaries.
 The macular region gets its blood supply by small twigs from the
sup.& inf. temporal br.of CRA. sometimes cilio-retinal artery(a br
from ciliary system of vessels)is seen originating in a hook
shaped manner within the temporal margin of the disc. it runs
towards the macula and supplies it, thus when present, It helps
to retain the central vision in the event of occlusion of CRA.
 THE RETINAL VESSELS ARE END ARTERIES.ie they do not
anastomose with each other.h owever,anstomoses between the retinal
vessels and ciliary system of vessels does exist(in the neighbourhood of
lamina cribrosa)with the vessels which enter the optic nerve head from
arterial system of zinn or haller.
 The terminal fundus arterioles bend sharply and dip almost vertically
into the retina,forming the capillary network arranged as follows In most of the extramacular fundus,there are 2 retinal capillary
networks- a superficial and a deep.
 The superficial network lies at the level of NFL and deep network lies
b/n INL & OPL. deep network is more dense and complex than
superficial.
 There are anastomotic capillaries which run from one to another.
peripherally,as the ora serrata is approached, capillary network is
reduced to a scanty single layer.
 In the parafoveal zone-capillary network is especially
well developed and is three layered. however, there
exists a capillary-free zone in the fovea, k/n as
FOVEAL AVASCULAR ZONE(FAZ)of about 500um in
diameter.
 In the peripapillary region,the capillary network
becomes 4-layered to support the extremely thick nv
fibre layer characteristic of this region.
 BLOOD SUPPLY OF THE VISUAL PATHWAY The visual pathway receives its blood supply from the
two arterial systems,carotid and the
vertebral,connected to each other at the base of brain
by the arterial circle of willis.
 SIMILAR TO BRAIN, visual pathway is mainly
supplied by pial network of vs except the orbital part
of optic nv which is also supplied by an axial system
deri.from CRA.
 Optic nerve:
 Intraocular (1mm)
 Intraorbital(30 mm)
 Intracanalicular(6-9mm)
 Intracranial (10 mm)
Arterial supply :
 Mainly by posterior cilliary artery except for nerve fiber layer –
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which is supplied by retinal circulation.
Nerve fibre layer is mainly supplied by arterial branches of
central retinal artery.
prelamilar and lamilar region is supplied by posterior cilliary
arteries.
Retrolamilar region supplied by both cilliary and retinal
circulation. Anastomosis between retinal vessels and cilliary
system of vessels does exit.
Arterial anastomosis between 2-4 or more short posterior cilliary
arteries,which lies in sclera around optic nerve called circle of
zinn-haller
Venous drainage:
 Mainly by central retinal vein
 Central retinal vein is tributary of superior ophthalmic
vein ,it wil terminate in cavernous sinus.
 Small portion by choroidal system
 Intraorbital part by 2 system of vessels-
periaxial and an axial.
-periaxial system of vs supplying this part of optic nv is
derived from 6 br of ICA namely Ophthalmic A,Long
Posterior Ciliary A,Short Posterior Ciliary A,Lacrimal A &
CRA before it enters optic nv and circle of zinn.
-axial system of vs supplying axial part of optic nv is derived
from-intraneural br of CRA, central collateral arteries
which comes from CRA before it pierces the nv. & central
artery of optic nv.
 The capillary network for the optic nv is derived from
both the systems.
 Intracanalicular part-
-supplied only by the periaxial system of vessels.
 -the pial plexus in this part is fed mainly by the br from the ophthalmic artery.
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 Intracranial part Arterial supply this part is exclusively supplied from the periaxial system of vs.
 the pial plexus here is contributed by 4 sources-
-br from ICA either directly or through recurrent br of Anterior Superior Hypophyseal
A(supply inf aspect of optic nv containing lower retinal fibres);br from Anterior Cerebral
A(supply sup aspect of optic nv containing upper retinal fibres);small recurrent br from
Ophthalmic A and small twigs from Anterior comm. A .
 Venous drainage-
the venous drainage in the optic nv head is primarily by CRV.
 Orbital part is drained by peripheral pial plexus and also by CRV in the distal part.
 Intracranial part is drained by pial plexus which ends in ant.cerebral and basal vein.

 BLOOD SUPPLY OF OPTIC CHIASMA Arterial supply-
 Vessels may enter directly or indirectly through the pial plexus.
 Main supply from branches of ant.cerebral and Int Carotid A
with some contributions from others as follows Ant.cerebral and ant.commu.art-superior aspect
 Branches from ICA,Ant Sup Hypphyseal A and Post.commu.ainferior aspect
 Antero-inferior margin of chiasma-by the br.of ophthal.art.
 Venous drainage Sup.aspect-drained by-sup.chiasmal vein-ant.cerebral v
 Inf.aspect-by pre-infundibular v-basal vein
 Arterial supply Pial plexus supplying optic tract receives contribution
from Post.commu.artery,ant.choroidal art.and
branches from middle cerebral artery.
 Though no anastomosis but considerable overlap b/n
ant.choroidal art.,and the branches of MCA.so no
hemianopia d/t occlusion of ant chroidal A.
 Venous drainage Sup. Aspect-Ant.cerebral vein
 Inf. Aspect-Basal vein
 Arterial supply-
 Post.cerebral artery-postero-medial aspect-thus nourishes
the fibres coming from the sup.homonymous quadrants of
the retina.
 Anterior choroidal artery-solely the anterolateral aspectfibres coming from inf.homonymous quadrants of retina.
 Region of hilum-which contains macular fibres-by the rich
anastomosis from both the posterior cerebral and the
anterior choroidal arteries.
 Venous drainage-
Basal vein
 Arterial supply Anterior choroidal artery-through the perforating
branches-optic radiations anteriorly over the roof of
inferior horn of lateral ventricle.
 Deep optic artery{br.of MCA}-middle part when they lie
lateral to descending horn of lateral ventricle.
 Calcarine branches of Post Cerebral A and perforating
branches from Middle Cerebral A-posterior part as the
fibres spread out to reach the visual cortex.
 Venous drainage-
-by the Basal vein and in some part by middle cerebral
vein
 Arterial supply Mainly supplied by posterior cerebral artery-via calcarine artery
supplemented by its other two branches-posterior temporal and
parieto-occipital arteries.hence macula is spared in the event of
calcarine art.occlusion.
 The terminal branches of MCA supply the anterior end of
calcarine sulcus and lateral aspect of the occipital pole.
 At the posterior pole,rich anastomosis present b/n the MCA
and PCA.
 Venous drainage Medial aspect-Internal occipital vein –great cerebal v of Galen
and Straight sinus.
 Superolateral aspect-inferior cerebral v-cavernous sinus
 Orge, et. al. have shown that detachment of rectus
muscles can reduce blood flow in the ophthalmic
artery 30%, presumably because of ‘downstream’
effects. Such a change in susceptible individuals could
lead to acute anterior segment ischemia.
 In clinical practice, it is not known with certainty what
factors ultimately influence the postsurgical dynamics
of anterior segment circulation in a given case. Some
useful guidelines follow:
 When a muscle is detached and reattached, anterior
ciliary vessels do not recannulate.
 Because there are no long posterior ciliary arteries
superiorly or inferiorly, detachment of the superior or
inferior rectus muscles disrupts iris vessel filling more
than detachment of the horizontal recti.
 Older, vascularly-compromised patients may be more
likely than young, healthy patients to develop anterior
segment changes after eye muscle surgery.
 Iris angiography is a valid way to assess anterior
segment circulation at a given time, but it is not a valid
or practical predictor to determine what might happen
if eye muscles are detached.
 If anterior segment ischemia occurs, it should be
treated with atropine and frequent instillation of
topical steroids