Anatomy of retina

1. Anatomy of retina
By - Dr. Vikrant Singh (JR1)
Department of Ophthalmology

2. •Retina is the innermost thin delicate and
transparent layer of the eye.
•It is the most highly developed tissue of the eye.

3. Embryology of retina
• The embryology of the human
eye is 1st seen in the 22nd day
of the intrauterine life, as
bilateral invagination of the
neuroectoderm of the
forebrain to be precise the
diencephalon.
• The bilateral invagination of
the diencephalon give rise to
the optic groove or optic sulci.
The groove keeps on growing
to form the optic vesicles,
which grows towards the
ectoderm.

4. • At day 33 the optic disc starts to invaginate, forming optic cup. The
ends of the optic disc remains unfused to create choroidal fissure. The
choroidal fissure transmit the Hyaloid artery and vein which later will
become the central retinal artery and Vein after the closure of the
fissure.

5. •The 2 layers of the optic cup formed (external and internal) is
separated by the intraretinal space which is continuous with
the optic stalk and 3rd ventricle. The two layers are of
different size as the outer being thinner than the inner.
•The outer layer becomes pigmented layer and the inner layer
becomes neural layer. The two layers are separated by the
intraretinal space.
•The optic cup is the divided into the anterior 1/5 and 4/5
posterior.
•The anterior 1/5 will later differentiate to the ciliary body and
the iris.

6. Gross anatomy
•Extent – from optic disc to ora serrata.
•Surface area – 266 mm²
•Thickness: Thickest near optic disc :0.56 mm, 0.18 to 0.2 mm
near equator and 0.1 mm at the ora serrata
•Retina appears purplish red due to the visual purple of the rods.

7. Optic Disc
Macula
Peripheral
retina

8. • Opticdiscisimportantlandmarkin retinaandpalepink incolor.
• Thesite whereganglioncell axonsaccumulate and
exit the eye
• Theopticdisclacksall retinal elementsexceptthe nerve
fiiberlayerandaninternallimitingmembrane
• VerticallyovalVerticaldiameter-1.8mm
• Horizontal diameter-1.5 mm
• Anteriorposteriorwidth-0.7-1mmin length
Palecenterarea-physiological cup
• Horizontallyoval
• Freeofnerve axon(cup)-0.3mm
• NormalCDR= 0.4
Aroundtheopticcupisneuroretinal rim
• Pinkandsharpperipheral margin
• Containnerve axon
• Broadinferiorrimfollowedbysuperior>nasal>temporal(ISNT rule)
OPTICDISC-SURFACEANATOMY

9. s
• Optic disc contains no photoreceptor; thus it
representsthephysiologicalblind spot.
• It is paler thanthe surrounding retina becausethere is
noRPE.
• Thepale-yellow/salmoncolorofdiscisdueto
combinationofthesclerallaminacribrosaandthe
absenceofcapillarynetwork.
PAPILLEDEMA is edema of the optic disc secondary to
an increasedinintracranialpressure (ICP).
• pressure within the meningeal sheaths causes fluid
to accumulate within the fibers so that they swell
leading toblurringofthedisc margins
• Edema of the optic disc from any other cause is
referredto assimply“edemaofthe opticdisc.”
CLINICALCORRELATES-OPTIC
DISC

10. GROSSANATOMY-REVIEW
Grosslyretinaisdividedintotwo parts;
Central
retina
1. Macula
2. Fovea
3. Foveola
4. Umbo
5. Parafovea
6. Perifovea
Richincones,hasmoreganglioncells
per areathanelsewhere,andisa
relatively smallportionoftheentire
retina.
Clinical
function
• Designedforfinevisual
acuity,
• Photopicvision
• Stereopsis‘,
• Colorvision
Peripheral retina
1. Nearperiphery
2. Midperiphery
3. Farperiphery
4. Oraserrata
Makesupmostoftheretina,and
rods dominate
Clinical
function;
• Designedforgrossvision and
• Scotopic/nightvision
• Sensitivetomotionand
stimulates

11. CENTRALRETINA
Macula-
-Demarcatedby
superior andinferior
temporal arterial
arcuate
-Ellipticalshape
horizontally
-Averagediameterof
about5.5mm/3.5DD
-Areacentralis
correspondsto
approximately15-18°of
visualfield
Fovea
-centerofmacula
-It hasadiameterof
1.5-1.85mm/1DD
-Represents5° ofthevisual field
Photoreceptorlayer-entirelycones
Foveola
-Centreoffovea( highestvisualacuity)
-4mmtemporaltothecentreofthe
optic disc
andabout1mmbelowthe horizontal
meridian
-0.35mmin D/0.3-0.4DD
-correspondsto1° of
visual field
-Umbo(Centeroffoveola)
correspondstolight reflex
1mm
4
mm
Parafovea
-0.5mmaround
the fovea
Perifovea
-1.5mmaround
the parafovea

12. MACULA Macula-Darkyellowareainthecentral retina and
ismadeupofmorethan1layerofganglioncells.
Protectscentralvisionbyfollowing
characteristics;
1. Highlypigmentedtall epithelialcellsof
RPE(highestpigmentationofentireretina)-
whichgivedark macula
2. Densepigmentationhelpstoreduce
scattering of light
3. Thechoroidalcapillarybedalsoisthickestin
themacula
4. Ithasalsoyellowishhueduetohighest
concentrationofxanthophyll pigments
Functionofxanthophyll pigments;
• Actasfilters, absorbsshortwavelengthvisiblelighttoreducechromaticaberration
• Antioxidanteffect,
• ProtectiveroleagainstUVRdamage.

13. Centraldepressioninmacula- fovea
• Foveolais formedbylateral displacementofretinal
neuronsleavingonly photoreceptorsinthecenter.
(foveolarnuclearcake)
• Theinnernuclearlayerandganglioncelllayerare
displacedlaterallyandaccumulateonthecurvedwalls
of thefoveacalledClivus
• Thefoveahasthehighestconcentrationofcones
(199,000-300,000cones/mm)
• Thephotoreceptorfibers(cones)becomelongeras
they deviateawayfromthecenter;thesefibers are
called Henle’s fibers
FOVEA
(Fovea
)
Foveol
a

14. CTN… • Sixlayerspresentinthefoveolaare ;
(1)internal limitingmembrane (2)Henle’sfiber
layers
(3) ONL(whichcontainsabout10rowsofconenuclei),
(4)externallimiting membrane,
(5)photoreceptorlayers
(6) RPE
Note;
• Thinfoveallayersandcompactconephotoreceptor
helpstoformsharpestvisionand steoropsis
• Fovealreflexis causedbytheparabolicshape
formed bythe clivus.
• Lossoffovealrefleximpliesdisruptionofneural
layers

15. PRisdividedintofourparts
1. Nearperiphery
• (1.5mmaroundthemacula )
2.Mid-periphery
•(3mmaroundthenearperiphery)
3.Farperiphery
• Extrendsfromequatortotheora
serrata
4.Oraserrata.
PERIPHERALRETINA(PR)
5.5m
m
Macul
a 1.5mm
3m
m
• Anatomicalequatorislocatedapproximately2DDfromtheentrance
of vortexvein/about24mmfromthecenterofopticdisc

16. ORASERRATA It is the serratedperipheral margin
where the retina ends and ciliary body
starts
Description Length
Widthofora
serrata
2.1mmtemporally
0.7-0.8mmnasally
Locationfrom
limbus
6mmnasally 7mm
temporally
From equator 6-8mm
Fromoptic disc 25mmnasally

17. RETINALMICROANATOMY
Retinalpigment
epithelium;
Photoreceptorlayerofrodsand
cones; Externallimiting membrane;
Outernuclearlayer; Outerplexiform
layer;
Innernuclearlayer; Innerplexiform
layer; Ganglioncelllayer; Nervefibre
layer;
Internallimiting membrane.
(
perception
elements)
(conductive
and
associative
elements)
(conductiv
e
elements)
Retina composed of 10 layers- outward to inward

18. • Infarperipheryit continuesforwardasthepigmentedlayeroftheciliary
epithelium
• Outermost singlelayerofhexagonal
shaped cellscontaining pigment
• Locatedbetweenthehighlyvascular
choriocapillariesandtheoutersegmentsof
photoreceptorcells
• 4-6millionRPEcellspereye.
• Extendsfromtheoptic disc totheora
serrata,
RPE
RPE
Bruch’s
membran
e
Choriocapillarie
s
Photorecepto
r layers

19. Clinical coorelates;
• Nospecializedjunctionalcomplex betweenRPEand
photoreceptors-loosely adhered
• Createspotentialspace(subretinalspace-prone for
RD)
RPE-ULTRASTRUCTURE
RPEarehexagonalcellswiththreeCellSurfacescharacteristics:
1.Apicalsurface–innersurface 2.Paracellular
surface-intercellularsurfaces 3.Basalsurface–
outer surface
Apical surface
• Hasmicrovillousprocesses-IncreasesSurface area
• Interdigitatewithoutersegmentsofphotoreceptor
cells(1to45)
• Containsmelaningranules–moreinmacularregion
• OtherRPEpigmentislipofuschin.

20. Paracellular surface;
• Containstightjunction(ZonulaOccludens&adherens,gap
junctions)
• Junctionalcomplexformblood-retinalbarrier
• Maintainsretinalhomeostasisandpreventsfromtoxic damages
Basalsurface;
• Attached toitsbasal lamina,the
lamina vitrea of Bruch's
membrane.
• Nutrients from choriocapillaries
difuses to RPE through basal
lamina

21. RPE-FUNCTION
• Visual pigmentregeneration
• Phagocytosisofphotoreceptors
• Formationofbloodretinalbarrier
• Transportofnutrientsandmetabolites throughthe bloodretinal
barrier
• Maintains integrityof subretinal space
• Providesmechanical supporttophotoreceptors
• Manufactures pigment
• Regenerative and repairative function
Clinicalnotes
• Disruptionofbloodretinal barrierscausesretinaledemaeg.Macularedema

22. PHOTORECEPTORLAYERS
• 120million
• maximumdensityinringshapedzone5-6mmfromthefovea
(160,000rods/mm2)
• rod-freeatthefoveainan area of0.35mm
• -minimumdensity- periphery
• - lightsensitive molecule- rhodopsin
• (nightvision-scotopic vision)
Densityanddistributionofphotoreceptors
Cones-
Rods
• 6.5million
• densityis maximumatfovea
(199000cones/mm2)
• -minimumdensity-
periphery
-lightsensitivemolecule-
Iodopsin
(colorvision-photopic
vision)
Clinicalcorrelate
• Mutationofrhodopsininretinitis pigmentosacausesmaximumpigmentation3mmaround
the fovea
• Withadvancedofagethereisprogressivelossofphotoreceptors(rodsareaffectedmore
than
cone)-poornightvisionin elderly

23. MORPHOLOGYOF
PHOTORECEPTORS
Rods and cones are composed of several parts- six
main parts
1. The outer segment, containing the visual pigment
molecules for the conversion of light into a neural
signal;
2. Connectingstalk
3. Theinnersegment,containingthe metabolic
apparatus
4. Theouterfiber;
5. Thecell body-formsouternucleated layers
6. Theinnerfiber,whichendsinasynapticterminal-
outerplexiformlayer

25. STRUCTURE OF ROD CELL:
1. 40-60 µm long.
2. Outer segment is cylindrical- contains visual pigments and is
highly refractile.
3. Pigments are located in flattened double lamellae in the form
of discs.
4. Discs varies between 600 to 1000/rod cell. There are no
special attachments bet. discs or bet. discs and plasma
membrane.
5. Discs contain 90% of the visual pigment remaining is
scattered on plasma membrane.
6. Inner segment of the rod is thicker than the outer. It has two
regions.
a．Outer eosinophilic ellipsoid which contains
more mitochondria.
b．Myoid which contains glycogen as well as usual
organelles
Clinical notes;
• Rodneedgreatsensitivitytodetectthesmallamountoflight available
• Rodarenumerousandcontainsaboutamillionrhodopsinmoleculeineach
sac/disc

26. CONES-
MORPHOLOGY 1. Conical in shape
2. 40 TO 80 µm long
3. Cone at periphery is short but in central fovea it
is
tall and resembles rod
4. Outer segment contains photo pigments
called iodopsin.
5. Theconeoutersegmenthavemorediscs(1000-1200per
cone)thandorodouter segments
6. Lamellar disc are attached to the membrane
• Inner segment is similar to rod structures.
• Ellipsoid contains a large number of
mitochondria.

27. • Not a true membrane
• Composedof theterminal bars
(zonulaeadherentes) between
Muller cellsandphotoreceptors
• Fenestrated membrane
• Extends from the ora serrata
to the edge of optic disc.
Main function-
• Selectivebarrier for nutrients
• Stabilization of transducing
portion of thephotoreceptors.
OUTER NUCLEI LAYER(ONL)
• Formed by nuclei of rods and cones.
• Rod nuclei form the bulk of this layer.
EXTERNAL LIMITING MEMBRANE .
ONL
ELM
RPE
Muller
cells

28. OUTER PLEXIFORM LAYER:
• It marks the synapses between the
photoreceptors with the dendrites of
bipolar cells and processes of horizontal
cells.
• The outer plexiform layer is thickest at
themacula(consists of obliquefibres of
henle’s layer.
• Inthefoveathereareno synaptic
terminals, becauseconepedicles are
displaced laterally to theextrafoveal
region.
Func
tio
n-
• Tra
ns
m
is
s
io
na
nda
m
plific
a
tio
no
fe
le
c
tric
a
l p
o
te
ntia
l
• Thep
re
s
e
nc
eofnum
e
ro
u
sjunc
tio
ns
-
Aid
sintheho
m
e
o
s
ta
s
iso
fthere
tina
.
• Ac
ta
safunc
tio
na
l b
a
rrie
rtod
iffusio
no
ffluid
sa
ndm
e
ta
bo
lite
s

29. • Syna
pticte
rm
ina
l areform
e
db
ythe
photorec
e
pto
r te
rm
ina
l a
ndthedend
ritic
proc
e
ss
e
sofINL c
ells
• Therodsha
saroundo
roval c
yto
pla
sm
ic
expa
nsio
nsc
a
lledspheruleswithfe
wsyna
ptic
term
inals
• Co
neha
velargercytopla
sm
ice
xp
a
ns
ionsknown
a
s pe
dic
leswithm
ultiplesyna
pticte
rm
ina
ls
PHOTORECEPTORSYNAPTICTERMINAL

30. Located betweeen OPL and IPL
Consists of following 8-12 rows of cells:
• Bipolar cells- 9 types
• Horizontal- 3 types(H1,H11,H111)
• Amacrine
• Supportive Muller’s cells
Fourlayerscanbedistinguishedbylight microscopy
1. Outermostlayer-horizontalcell nuclei
2. Outer intermediate layer- bipolar cells
3. Innerintermediatelayer-Muller cell
4. Innermostlayer-amacrineandinterplexiformcell
nuclei.
INNERNUCLEARLAYER
NumerouscellsandextensivecellularconnectionofINLisessentialfor transduction
and
amplificationoflight signals.

31. Horizontal
cells
• Flat cells,
• Hasnumerousneuronal
interconnectionsbetween photo
receptor andbipolar cellsin theouter
plexiformlayer.
• highest concentration in fovea
HORIZONTALCELLS
Function-
• Mo
dula
tea
ndtra
ns
formvis
ua
l inform
a
tionre
ce
ive
d
fro
mthephotore
ce
p
to
rs

32. HORIZONTALCELLS
Dividedinto3 types
1. HI
• Has stout dendrites that connects only cones at triad and
rod spherules
•The HI cells connects morewith L-
cone andM-
cones 2.HII
• TheHII cells haveslimoverlapping dendrites and ashort
curved axon
• Connects all types of cones
3.HIII
• TheHlll cellsare30%largerthantheHIcells andcontact
morecones,butareotherwisesimilarwithH1

33. BIPOLARCELLS-1s
tORDERNEURON
• Orientedradiallyintheretina
• Locatedintheinnernuclearlayers andtheir
processesextendtothe outerandinner
plexiformlayers
• Receiveextensivesynapticfeedback from
amacrinecells
Function-
• Bipolarcellsrelayinformationfromphotoreceptorstohorizontal, amacrine,andganglion
cells.

34. Under light microscopy nine
types
a. Rod bipolar cells(RB)
bipolar(7
)
–
b．Invaginating
midget
smallest(MB)
c．Flat midget bipolar
d．Invaginating diffuse bipolar
e．Flat diffuse bipolar
f．On-centre blue cone bipolar
g．Off-centre blue cone bipolar
h．Giant bistratified bipolarGBB)
i．Giant diffuse invaginating bipolar
Rodbipolar interacts only with rod photoreceptor rest contacts with cones
Thereare about 35.68 million Bipolar cells in retinawith highest concentration at fovea

35. Clinical application;
• TheOFFbipolardepolarizesindarkandhyperpolarizesinlight- activatedbycones
• TheONbipolardepolarizesinlightandhyperpolarizesindark-activatedbyrods
• Bipolarcellstransferinformationtoretinal ganglioncells
• Bipolarscellswhichrespond with
depolarization(inactivation)areOFFbipolars
• Bipolarcellswhichrespondwith
hyperpolarization
(activatedstate)calledareONbipolars.
• OFFbipolars synapse in the outerpartof the IPL
• ONbipolarssynapse intheinner tier,closestto
the
ganglioncelllayer

36. Bipolar Cells
Type Connections Peculiarity
1. Rod Bipolar Cells
20%, Large soma
profuse
dendrites
Arborize only with rod
spherules
Axons of these bipolar cells
have synapses with soma
up
to 4 ganglion cells
2. Midget Bipolar cells
Small
Make connections only in
triads of cone pedicle
Invaginating- Deeply
invaginate cone pedicle
Flat- Makes superficial
contact
with cone pedicle
Axons synapses with
SINGLE
ganglion cell.
3. Diffuse- Makes contact with cone
pedicles only
Not with their triads
Axons synapse with number of
ganglion cells of all types.
4. Blue cone bipolar cells
5. Giant Bipolar cells
Innervate more than one cone
pedicle
Distinguished by extent of
their dendritic spread

37. AMACRINECELLS
• Situated within the innermost part of INL.
• Have a piriform body and a single process which
passes inwards in the IPL and forms connections
with the axons of the bipolar cells and the
dendrites and soma of the ganglion cells.

38. Muller’s cells
•Nucleus and cell bodies lie in inner nuclear layer but its outer
end extends up to the ELM and those from the inner end
reach the ILM.
•Provides structural support and contribute to the metabolism
of sensory retina.
•Role in various layers –
ELM – Forms ELM (junction between terminal part of muller
cell fibre and cell membrane of photoreceptors)
ONL – provide reticulum around cell somata.
OPL – form horizontal extending reticulum.
INL – reticulum around various somata.
IPL – horizontal reticulum.
INTERNAL LIMITING MEMBRANE – inner fibres take part in

39. • Consistsof synapses bet. Axons of bipolar cells,
dendrites of ganglion and amacrinecells.
• Twoelements arepresent at synapseinan
arrangement that isknown asa 'dyad‘
• In this typeof synapse, thebipolar cell
contactstwoprocesses, onefroma ganglion
cell andtheother from an amacrinecell
INNERPLEXIFORMLAYERS
Twodistinctsyna
ps
e
sa
reuniquetothea
m
a
c
rinece
llsinIPL:
1. There
c
ip
roc
als
yna
p
se
• Conne
c
tinga
m
a
c
rinec
ell b
a
c
ktothene
a
rbybipolarcell te
rmina
l,
sug
ge
stingaloc
al fe
ed
ba
c
k m
e
c
ha
nis
mb
e
twe
e
nthe
s
ec
ells.
2.Theseria
l syna
ps
e
-
• Am
a
c
rinece
ll proc
e
sssynap
singwitha
na
dja
ce
nta
m
ac
rinece
ll proc
e
ss
Thereciprocal
synapse
Serialsynapse

40. •
• Singlerow in Peripheral retina
• At the edge of foveola (macula)
it is multi layer(6-
8 layered) and
on temporal side of disc it has
two layers.
• It is absent in foveola and optic
disc
Ga
nglionce
llstra
ns
m
itss
ig
na
l fro
mthebipo
la
rce
ll tothela
te
ra
l ge
nicula
teb
o
dy
1.2 million ganglion cells arepresent in theretinaeach with asingle
axon
GANGLIONCELLLAYER-
2nd order neuron of ganglion
cells lie in this layer

41. 2.Mganglion/Parasolcells-polysynaptic becausethey
makesynapsesoverawidearea.
• Theysynapsewithall typesofbipolarcellsexcept
the midget bipolars
• Mcellsconstitute5%ofthetotalganglioncell
populationatthefoveaand20%attheperipheryof
the retina
18typesofganglioncellsdescribed-twomaintypesare
1.Pganglioncells-
• Monosynaptic ganglion cells, show
dendrites that synapse exclusively with
axon terminals of midget bipolar cells and
amacrinecellprocesses
• Pcellsareconcentratedincentralretina,
• Constitute 80% of the ganglion cell
population.

42. PGanglioncells
• ThePganglioncellsprojecttothe
parvocellularlayers
• provideinformationaboutfiinedetail
andcolour
Mganglion cells
• Mganglioncellsprojectsto
Magnocellularlayersof LGN
• Mcellshaveexpansiveprocessesandcoveralargeareaofretina,they
can respondrapidlytomovingorchangingstimuli.
• Sensitivetoluminancechangesindimillumination(scotopic conditions)

43. NERVEFIBERLAYER(stratumopticum)
• Consistsoftheunmyelinatedaxonsof
theganglioncells
• Opticnerveconsistsofapproximately
1.2-1.5millionaxonsofretinal
ganglion cells
• Theircourserunsparalleltotheretinal
surface
• Thefibersproceedtotheopticdiscatarightangle,andexittheeye
throughthelaminacribrosaastheopticnerve.
• Thefibersgenerallyareunmyelinatedwithinthe retina

44. ARRANGEMENT OF NERVE FIBRES IN THE RETINA
1. Fibres from the nasal half of the retina come directly to the
optic disc as superior and inferior radiating fibres (srf and irf).
2. Fibres from the macular region pass straight in the temporal
part of the disc as papillomacular bundle (pmb).
3. Fibres from the temporal retina arch as superior and inferior
arcuate fibres (saf and iaf) with a horizontal raphe in between.
• Thenervefibrelayeristhickestatthenasaledgeofthedisc,whereit
measures 20-30
microns
• Thethicknessdecreasedwithincreasingdistancefromthedisc
margin,becoming8to 11micronsjustposteriortotheoraserrata
• Thepapillomacularbundlerepresentsthethinnestportionofthe
nervefibrelayeraround theoptic disc

45. ARRANGEMENT OF NERVE FIBRES OF THE OPTIC
NERVE HEAD:
• Fibres form the peripheral part of the retina lie deep in
the retina but occupy the most peripheral(superficial)
part of the optic disc.
• While the fibres originating closer to the optic nerve
head lie superficially in the retina and occupy a more
central (deep) portion of the disc.
THICKENSS OF NERVE FIBRE LAYER AT THE DISC:
• Thickness of the nerve fibre layer around the different quadrants of the optic disc
margin progressively increases in the following order:
1. Most lateral quadrant (thinnest)
2. Upper temporal and lower temporal quadrant
3. Most medial quadrant
4. Upper nasal and lower nasal quadrant (thickest)

46. CLINICAL SIGNIFICANCE OF DISTRIBUTION AND THICKNESS OF
NERVE FIBRES AT THE OPTIC DISC MARGIN:
1. Papilloedema appears first of all in the thickest quadrant (upper nasal
and lower nasal) and last of all in the thinnest quadrant (mostlateral).
2. Arcuate nerve fibres are most sensitive to glaucomatous damage,
accounting for an early temporal arcuate visual scotoma inglaucoma
3. Macular fibres occupying the lateral quadrant are most resistant to
glaucomatous damage and explain the retention of the central vision till
end.

47. INTERNALLIMITING MEMBRANE
• Theinternallimiting membraneformstheinnermost
layer oftheretinaandtheouterboundaryofthe
vitreous
• Boththeretina andthevitreous contribute tothe
formation ofthis membrane.
• Consistsoffour elements:
(1) collagenfibrils
(2)proteoglycans(mostlyhyaluronicacid)ofthe
vitreous;
(3)thebasement membrane;
(4) theplasmamembraneoftheMullercells andpossibly
otherglial cellsofthe retina
• Intheposteriorretinatheinternallimitingmembraneattainsathickness of0.5-2.0 Um.
• It continues uninterruptedatthe fovea whereit is thickest
• Atthe peripheryof the retina, the membrane is continuous with the basal lamina ofthe ciliary
epithelium

48. Blood supply of retina
• – choriocapillaries
• – central retinal arteries.
• – from both choriocapillaries ( by
diffusion) and central retinal arteries.
• is an avascular area mainly supplied by the
choriocapillaries.
• gets supply from small branches of sup n inf
temporal branches of central retinal artery. Sometimes
CILIORETINAL artery originates in hook shape manner from
temporal border of disc and supplies macula.
•Retinal arteries are end arteries.
•However forms anastomosis between retinal vessels and