This is a detailed power point presentation about anatomy of Retina for post graduate students. Deals with anatomy, structure, cell types, organization of retinal cells, structure of macula, blood supply of retina, number of rods and cones etc

1. Anatomy of the Retina
Vivek Wani MS, FRCSEd
Consultant Vitreoretina surgeon
KLES DR PRABHAKAR KORE HOSPITAL AND MRC
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2. RETINA
• IN Latin Rete means
net- it looks like net in
a crude specimen
• It is the light sensitive
part of the eye
providing us the vision
• Part of the CNS
• Hence many diseases
affecting CNS affect it
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3. Retina
• It is the only part where you see the blood
vessels live in a non invasive manner &
examine the retina
• 80% of sensory input to the brain is estimated
to come from retina
• Half of all neural tissue in the brain deals with
vision directly or indirectly
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4. Anatomy of the retina
• Gross anatomy
• Embryology
• Layers of the retina &Histology
• Blood supply
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5. Eye ball has a wall and cavity
Wall is made up of 3 coats
Outer Fibrous coat -
Anterior 1/6 clear cornea
Posterior 5/6-Opaque white sclera
Vascular coat-Uvea -middle coat
Iris (pupil)
Ciliary body
Choroid
Coats of the eye
Retina inner coat
It covers the 3/4 of the inner surface of the eyeball
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6. Retina dimensions
• It extends from the edge
of the ONH to the ora
serrata
• The RNFL in fact forms the
ONH while exiting the eye
• All other layers of retina
stop abruptly at the ONH
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7. All the layers of retina stop at ONH
except RNFL
which continues as ON
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8. What happens to the retina at the ora serrata?
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At Ora serrata
-neurosensory retina stops abruptly and continues as
single layered non-pigmented epithelium of the pars
plana of the ciliary body
The RPE continues as it is and is called pigmented epithelium of
the ciliary body
So ten layers of retina become only two layers of epithelium of
ciliary body

9. Ora serrata
• Ora is not straight line but has
broad serrated border
• Dentate processes are pointed
extensions
• Oral bays-are spaces between
dentate processes
• Dentate processes are more
prominent nasally than
temporally
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10. Externally where is the ora serrata?
• It roughly coincides
with insertion of
recti muscles
• Spiral of Tillaux
• Distance of ora
from Limbus (mm)
5.5 to 7.5
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11. Before we learn about layers of retina
• We should learn about
development of retina that will
make it easy to understand the
arrangement of the layers of
retina
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12. Development
of Retina
• The earliest stage of retina/eye development
is the formation of the paired optic vesicles
• They are projections on either side of the
forebrain- around 22 days of intrauterine life
• This vesicle is lined by neuroectoderm which
forms the retina, epithelia of CB and iris
• Mesoderm and ectoderm form other
structures of the eyeball
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13. Development of Retina
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These optic vesicles expand laterally into the
mesoderm of the head and develop a stalk-like
connection to the main portion of the
rudimentary central nervous system
Surface ectoderm thickens to
form a lens placode, a region
visible on the surface of the
embryo as a pit
Once the formation of the lens placode
has begun, the optic vesicle begins to
invaginate to form a cup-shaped
structure
The lens placode also becomes lens
vesicle and detaches from surface
ectoderm and occupies the cavity of
the optic vesicle

15. Development of retina
• Optic vesicle invaginates in the front to form
a cup
• It folds inferiorly too along its centerline,
optic stalk included, enclosing angiogenic
mesenchyme
• The gap inferiorly -optic or fetal fissure
• This mesenchyme forms the hyaloid artery
and vein, which supply the forming lens and
vitreous
• Also supply the developing retina later
forming the central artery and vein of the
retina
• The fetal fissure starts closing from 5th week
and the closure is complete by 7 th week
• The closure is complete with the most distal
apposition of these edges becoming the
pupil
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ONWOCHEI ET AL
SURVEY OF OPHTHAL
2000

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18. Optic vesicle is lined by a single layer
of neuro-epithelium
• As the cup invaginates and folds, it is forming
a doubled layer cup
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From Snell &Lemp

20. CONTRIBUTIONS FROM OPTIC VESICLE
• Posterior 4/5- form Retina
• The inner layer –becomes multilayered -neurosensory
retina-9 layers including light sensitive rods and cones
• Outer layer of vesicle –RPE layer
• Melanin pigments appear at about 4.5 weeks in RPE
• Anterior 1/5 gives rise to
 Inner layer- non-pigmented epithelium of pars plana and
CB, then forms the pigmented posterior layer of the IRIS
 OUTER LAYER- pigmented epithelium of pars plana and CB,
then forms the anterior layer of iris epithelium where it
gives rise to sphincter pupillae and dilator pupillae
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21. Development of Retina
• The embryonic cavity of the optic vesicle
become obliterated as these two layers come
to face each other
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22. Further Development of retina
• The inner layer starts differentiating in the fovea and
gradually involves the periphery
• The first cells to develop are the ganglion cells and their
fibers which exit the eye to form optic nerve
• Inner layer of optic vesicle develops inner marginal zone
and an outer nuclear zone
• The outer nuclear zone cell invade the marginal zone and
form outer and inner neuroblastic layers
• The inner neuroblastic layer- ganglion cells, amacrine cells
and Muller cells
• Outer neuroblastic layer gives rise to- horizontal cells,
bipolar cells and cone and rod cells
• Photoreceptors continue to develop after birth too
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23. Peter Quin N Wijnholds
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24. Neuroretinal development
• Overall, the cell classes can be divided into two phases of generation
• In the first phase, the ganglion cells, the cones, and the horizontal cells
are generated
• In the second phase of histogenesis, the rod photoreceptors, the bipolar
cells, and the Müller glial cells are produced by the progenitor cells
• Amacrine cells are primarily generated in the later phase, but many
amacrine cells become postmitotic at the same time as ganglion cells are
generated, so these cells do not fall as neatly into one or the other phase
• Despite this seeming regularity in histogenesis, it should be noted that
there are distinct central-to-peripheral gradients of histogenesis, and that
peripheral retina may still be in the first “phase” at the time central retina
is generating later cell types
• From Thomas Ray
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25. Structure of the Retina
It is made up of two main layers
The outer layer –single
layer of cells of -Retinal
pigment epithelium -RPE
It has melanin pigments
Is adherent to Bruch’s
membrane of choroid
Inner layer- Neurosensory
retina
Vascularized
Transparent
Histologically it has 9 layers
Both are apposed to each other and a potential space
exists between the two
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amples
Examples where the potential space is open due to abnormal fluid collection

27. Separation of neurosensory retina
also occurs in Rh RD
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28. The RPE pigmentation and choroidal vascularity
give it the reddish color
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29. Retina relations
• Anterior or internal to the retina is in contact
with vitreous and externally with choroid
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31. Thickness of retina
• The average thickness is 250-µm thick at
temporal margin of the optic nerve
• Thickest at 400 µm in the macular area around
the fovea –para-fovea
• Central foveal thickness is around to 150 µm
• Thinner at equatorial region and at ora it is 80
µm
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32. OCT thickness at fovea
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33. Measurements of retina
• The total retina is a circular
disc of approximately 42 mm
diameter
• An area of approximately
1100-1499 mm2
• Limbus to ora 5.5 to 7.5 mm
• Equator is located 6-8 mm
posterior to the ora serrata
• Macula is located 18-20 mm
posterior to the equator
• Average distance from ora
serrata to the ONH is about
32.5 mm temporally and 27
mm nasally --arc length
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35. Retinal landmarks
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Macula
FROM CENTER OF EYE HEALTH WEBSITE

36. Regions of retina
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From Progress in Retinal and Eye Research ·
October 2018

37. Important areas of retina
• ONH
• MACULA
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38. Optic Nerve
Head(ONH)
• Also called as optic disc
• It is circular pinkish white
• Exit site of the nerve fibers of the ganglion cells
• Entry point of retinal blood vessels
• Situated about 4.5 to 5 mm nasal to the center of
the retina -fovea
• There is no retinal tissue except NFL and there is
no choroid
• It is 1.5mm-hx 1.75 mm-v
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40. Posterior pole or anatomical macula
• Posterior pole or anatomical macula- is the
area between temporal vascular arcades
• It is about 6 mm in diameter -17 d in angle
• Histologically macula is the region in the
posterior retina where ganglion cell layer is
more than 1 layer thick
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41. MACULA
• Macula lutea- refers to the presence of the
whitish yellow pigments -zeoxanthine and
lutein which are in the axons of the Henle’s
nerve fiber layer in the center of the macula
• They are supposed to filter ultraviolet light
and avoid damage to the foveal cones
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42. Regions in the macula
• Umbo
• Foveola-0.35 mm DIA
• Fovea-1.5mm DIA
• Parafovea-0.5 mmX2
• Perifovea-1.5mmX2
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43. Foveola and Umbo
• Foveola -0.35 mm
diameter
• Only cones n Muller cells
in this area
• No rods at all
• All other retinal layers are
missing here
• Roughly one degree of
visual angle
• This is the clearest area of
vision with highest visual
acuity and color vision
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44. Foveola
• Cones are slender and
tightly packed here
• 25000 cones are in this area
• Blue cones are also missing
from here
• NO blood vessels in this
area
• Umbo is the center of the
foveola
• It gives the sharp light
reflex we see when
examining the macula
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45. FOVEA
• Fovea-Clinical macula
• It is 1.5 MM in diameter
• It is a depression with a
gentle slope
• Slope is called as clivus
& acts as a concave
mirror and gives the a
circle of foveal reflex
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Depression is due to
migration away of inner
retinal layers –ganglion cells,
inner plexiform layer, inner
nuclear layer away from the
center to give clearer central
vision
Clivus

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From: Macular Hole Formation: New Data Provided by Optical Coherence Tomography
Arch Ophthalmol. 1999;117(6):744-751. doi:10.1001/archopht.117.6.744
Section through the center of the fovea. ON indicates the outer nuclear layer; OH, outer layer of Henle fibers; and INL, the inner
nuclear layer. In the 200 µm of the central area of the fovea, the outer cone fibers are separated from each other by the processes
of the radial fibers of Müller. The inner processes of the Müller cells occupy most of the inner third of the retinal thickness, thus
constituting the floor of the center of the foveola (reprinted with permission from Arch Ophthalmol).
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47. Parafoveal & Perifoveal area
Parafoveal area-outside fovea
• Dough nut shaped -0.5 mm broad
• Ganglion cell layer 5-6 layered
• Inner nuclear layer and outer
plexiform layer of Henle are
thickest
• For every 1 cone there are 4 rods
here
Perifoveal area- outermost part
• 1.5 mm dough nut shaped zone
outside Parafovea
• The ganglion cells become
gradually less here
• For every 1 cone there are 100
rods here
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48. FAZ
• The fovea shows the
vascular architecture
that divides and leaves
the central portion of
the fovea without any
blood vessels
• The foveal avascular
zone-FAZ- is around 500
microns in diameter on
FFA
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49. Retina outside the macula
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From Progress in Retinal and Eye Research ·
October 2018

50. Retina outside the macula
• Retina becomes progressively thinner as we
go to the periphery
• The peripheral retina near ora may be
avascular for 1 DD
• Important area for retinal degenerations and
other retinal pathologies
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Retinal structure
There are 4 layers of cells
Ganglion cells
Bipolar cells
Photoreceptor cells &
Retinal pigment epithelial
cells
Three layers of fibres
1-Retinal nerve fibre layer-from ganglion cells
Two layers of nerve fibre where synapses occur
Plexiform layers because of network like structure
2-Inner plexiform layer
3-Outer plexiform layer
Histologically there are few more recognizable layers
Retina is customarily divided in to ten layers
There are other cells that sneak in 4
layers of cells
Muller cells
Horizontal cells
Amacrine cells
Neuroglia cells

52. Layers of the retina-from vitreal side to scleral
side
• Inner limiting membrane
• Retinal nerve fiber layer
• Ganglion cell layer
• Inner plexiform layer –synapses
• Inner nuclear layer (nuclei of bipolar
cells)
• Outer plexiform layer –synapses
• Outer nuclear layer (nuclei of
photoreceptors)
• External limiting membrane
• Layer of photoreceptors (rods and cones)
• Retinal pigment layer (RPE)
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55. 1) RPE layer
• Single layer of hexagonal cells-3.5 million cells
• Rest on a basement membrane that forms inner
most part of Bruch’s membrane of choroid
• RPE cells contain melanin pigments-hence
pigmented
• The apices of RPE cells have villi which envelope
photoreceptors
• Villi around the cones are longer >villi around
rods
• Adjacent RPE cells have tight junctions between
them near apices -zonula occludens -outer
retinal barrier –keeps away noxious materials
from entering retina
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56. RPE CELLS
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57. RPE cells
• Large round nucleus
• Cytoplasma contains-melanosomes, lipofuscin
granules and phagosomes, endoplasmic
reticulum and mitochondria
• Large number of mitochondria and
endoplasmic reticulum -- high rate of
metabolic activity
• RPE usually does not regenerate but in times
of injury or inflammation it can proliferate
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58. RPE cells
• Approximately 3.5 million RPE cells in the retina
• There are 5000 RPE cells/ sq mm in fovea and are 16 mu in
dia & taller
• In periphery 2000/sq mm and 60 mu in diameter and thinner
• One RPE cell is in contact with around 45 photoreceptors
• One RPE cell digests nearly 4000 discs of outer segments /day
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59. Zonula occludens
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60. RPE CELLS-Functions
• Transport/diffusion of glucose, oxygen, vitamin A and other
nutrients to the photoreceptors
• Pigments absorb light -prevent scattering of light in eye
• Outer retinal barrier-ZO -prevents toxins from entering retina
• Maintenance of retinal adhesion- pump out water from subretinal
space, villi hold cones &rods-prevent RD
• Replacement of the outer segments of the photoreceptors and take
part in Vitamin A cycle
• 11-cis-retinal becomes all trans retinal in photoreceptors
• All trans retinal is changed to retinol and is transported to RPE cells
• RPE CELLS isomerize all trans retinol to 11-cis-retinal and transfer
back to photoreceptor cells
• Regeneration and repair after injury or surgery
• Synthesis of growth factors –VEGF, PEDGF
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67. What are photoreceptors and what are rods
and cone CELLS?
The rod and cone cells are made
up of
• Photoreceptor – layer of
photoreceptors (rods & cones)
-Outer segments
-Inner segments
• Cell body -ONL
• Inner connecting fiber–OPL
• Axon terminal- pedicle in cone
and spherule in rod -OPL
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68. 2) Layer of photoreceptors
• Rods and cones are
modification of cilia in
embryological state
• They act as light receptors
–photoreceptors
• Rods involved in night
vision
• Cones involved in day
vision and color vision
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69. Photoreceptors -Rods and cones
• There are 110-125 million rods and about 5-6.8
million cones in the retina
• In the foveola -0.35 mm-1.2 d of visual angle
 only cones are present -25000 & no RODS
 No blue cones in this area
 Gives maximum visual acuity and color vision
• The density of the cones – foveola- 2-3 lacs/sq mm,
fovea- 20000/sq mm and 5000/sq mm outside fovea
• Fovea -1.5 mm- 110, 000 cones – 1.5 % of all cones
in retina---40% of visual cortex devoted to it!
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71. Number of rods and cones
• Cone density highest at center-umbo
• Rod density is highest at about 18 degrees
eccentricity
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72. Rods and cones
• Foveal cones are tiny- 2.3 micron in diameter,
packed closely in hexagonal (honeycomb)
fashion
• Cones become larger and packed less densely
away from fovea
• Rod photoreceptors fill up the spaces between
the cones
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73. Number of photoreceptors
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74. ROD CELLS
• Length- 100-120 mu , 2 mu wide
• Cylindrical shape - rod
• Rod cell is made up of the
 Photoreceptor
 Outer fiber-longer in rod than cone
 cell body contains nucleus-ONL
 inner fiber-which ends in spherule
 Inner fiber and spherule are in the
outer plexiform layer –OPL
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75. Cone cells
• It’s structure is similar to
rods
• Its size is 60-75 mu in length
• The outer segment is
conical –hence cone-except
in foveal area where it
resembles rods
• The outer connecting fiber
is shorter
• The cell body is in ONL
• The inner connecting fiber
ends in pedicle -OPL
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76. Photoreceptors
• Has two parts-- Outer segments and
inner segments
• Outer segments contain photopigment
embedded –photosensitive part
• Photopigment is embedded differently
in the rods and cones
• In cones the cell membrane itself
invaginates to form layers -cone opsins
are embedded in the membrane of the
invaginated membrane
• In rods they are embedded in discs
which are discrete and stacked up on
each other like coins and are present in
a tube of the cell membrane
• In rods there are 600-1000 discs
• Inner segments are the energy houses
and manufacturing units
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77. Rods and cones
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78. Photoreceptors
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79. Photoreceptors-outer segments
• The rod and cone outer segment discs are
constantly being replenished
• Rod outer segment discs are shed at the onset
of light (in the morning)
• Cone outer segments are shed at the onset of
darkness (at dusk)
• Rod outer segments are renewed every ten
days
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82. Rods and Cones-Inner segments
• Has two parts
 Inner Myoid-
endoplasmic reticulum,
Golgi apparatus,
produce discs of outer
segment
 Outer Ellipsoid- large
number of
mitochondria which
supply energy for
photoreaction
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85. Characteristic Cones
Photopic (color)
Rods
Scotopic (black & white)
Shape Tapered tip Blunt tip
Number ~5 -6 million ~100 -110million
Distribution Throughout retina, but
concentrated in the fovea
None in the the foveola, but
concentrated around the fovea
Lighting conditions
required for best functioning
Well-lit Dimly-lit
Relative number of
receptors for each ganglion
cell (convergence)
Few Many
Acuity Excellent Poor
Sensitivity Poor Excellent
Disc shedding Evening Morning
Photopigment Three types Rhodopsin
Dark adaptation Rapid, with high threshold Slow, with low threshold
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86. Outer limiting membrane (OLM) or
external limiting membrane ELM
• Not a true membrane
• Instead, it's the site of numerous junctions-
zonula adherence-- between the plasma
membranes of the inner segments of the
photoreceptor at their bases and the Muller
cells
• It appears in light microscopy like a row of
dashes with holes containing the
photoreceptor fibers joining the cell bodies
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89. 4) Outer nuclear layer
• This layer is the location for the cell bodies of
the rod and cone cells
• The rod cell bodies are small and cone cell
bodies are larger
• They are compactly packed and hence
produce a hypo-reflective layer in the OCT
• They send axons to the next layer
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90. 5) Outer plexiform layer
• In this layer the axons of
the rods and cone cells
synapse with Bipolar cells
• The rod axons end –
spherule
• Cone axons end in a foot
like fashion called pedicle
• Dendrites of the Horizontal
cells participate in this
layer of synapses
• The dendrites of the
bipolar cells, in particular,
comprise most of the outer
plexiform layer
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91. ROD SPHERULE
• Spherule of rods- It is
formed by a single
invagination
• It accommodates 2
horizontal cell processes
and one or more bipolar
dendrites
• Outer fibers are H cell
processes and inner one
is from Rod bipolar cell
• The spherule releases
glutamate as
neurotransmitter
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92. Cone pedicles
• Synapse with flat
bipolar, flat
midget bipolar,
invaginating
midget bipolar
and horizontal
cell processes
• They also
synapse with rod
spherules and
adjacent cones
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94. OPL- in fovea
• In the Fovea the bipolar cells and ganglion cells are
displaced outwards to make room for only the cones to
occupy the foveola
• Hence the axons of cones and are longer and form the
Henle’s layer –OPL
• Muller cell fibers are also here contributing to Henle’s layer
• As the cells have been displaced outside foveal fibers travel
radially out to reach their respective cells
• This layer is called Henle’s fiber layer
• This is the anatomical explanation of the macular star
arrangement of the hard exudates and flower petal
appearance of the CME
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97. FOVEOLA 0.35 MM DIAMETER
CONTANS
• RPE
• Photoreceptor layer
• ELM
• Muller cell processes
• Very few ONL cells
• Henle’s fiber layer-OPL
• ILM
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98. 6) Inner nuclear layer (ONL)
• Five important cell bodies are found here
Bipolar cells
Horizontal cells
Amacrine cells
Muller cell bodies
Inter-plexiform neurons
• The horizontal cell bodies lie in the outer aspect
of the layer
• The amacrine cell bodies lie in the inner aspect of
the layer
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99. Inner Nuclear layer
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100. INL
• Bipolar cell bodies have scant cytoplasma
• Its dendrites are sent to the OPL and there
they synapse with rod spherules, cone
pedicles and horizontal cells
• The bipolar send axons in to the IPL where
they synapse with ganglion cells, amacrine
cells
• Bipolar cells are of different types-11 types
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101. INL- bipolar cells
• Rod bipolar-is the only bipolar cell to contact
rods
• In central retina it contacts with 20 rods and in
periphery around 80
• Its axon synapses with amacrine cell in IPL
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102. Bipolar cell types
• Flat midget bipolar
• Invaginating midget
bipolar – contacts with
only one cone and then
relays information to one
ganglion cell only in the
fovea
• Diffuse cone bipolar, blue
cone bipolar, giant cone
bipolar are other types
• Gluatamate is the
neurotransmitter for
bipolar cells
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103. INL Horizontal cells
• Horizontal cells –have a peculiar structure -the
cytoplasm composed of special tubules and
ribonucleoprotein
• All their connections are in the OPL in a
horizontal fashion
• They synapse with cones, rods and bipolar
cells
• They have inhibitory effect at their synapses
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104. Amacrine cells
• Amacrine cells –have a lobulated nucleus and
have no special structures in cytoplasm
• Their connections are also horizontal and are
IPL
• They synapse with bipolar cells, ganglion cell
dendrites and their bodies, other amacrine
cells and inter plexiform neurons
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105. Muller cells
• Muller cells – their cell
bodies are scattered in
INL
• They form the framework
throughout the thickness
of the retina to support
and surround the nerve
cells and their axons and
dendrites
• They also form the OLM
and ILM
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106. Interplexiform neurons
• Their cell bodies are
among amacrine cells
• They connect the two
plexiform layers
• So have synapses in IPL
and OPL
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107. Inner Nuclear layer
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108. 7)Inner plexiform layer
• Here the axons of the bipolar cells synapse
with the dendrites of the ganglion cells
• Amacrine cells synapse with bipolar cell axons
and ganglion cell dendrites in the inner
plexiform layer
• There are six lamina of synapses recognized in
this layer
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110. 8) Ganglion cell layer
• The cell bodies of the ganglion cells are located in
this the layer, which has far fewer nuclei than the
inner or outer nuclear layers
• Size varies -28-36 mu
• There are nearly 1.2 million ganglion cells in this
layer and each one sends one axon to form the
RNFL which in turn form the optic nerve
• There are also Muller fibers which separate the
ganglion cells from each other
• There are different types of Ganglion cells
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111. Ganglion cell types
P cells or parvocells
• P1- is a midget ganglion cell which connects to
one midget bipolar cell that is connected in
turn to only one cone
• Concerned with color vision and high contrast
details
• Certain P1 cells receive input from two bipolar
cells
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112. P2 ganglion cells
• Has densely branched compact dendritic tree
in IPL
• Contacts with many bipolar cells
• Ends in parvocellular layer of LGN
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113. M cell –magnocellular
• Large cells ending in magnocellular layer OF
LGN
• They have large dendritic field in IPL
• Contact many amacrine cells
• Related to light sensitivity and movement
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114. 9) Retinal Nerve fiber layer
• The 1.2 million axonal fibers from the ganglion
cells
• Bundled together, run parallel to inner surface
of the retina, converging at the site of origin of
the optic nerve
• These axons are non myelinated till they exit
the lamina cribrosa
• Become myelinated as soon as they exit the
lamina cribrosa
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115. Myelinated nerve fibers
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116. NFL
• The NFL is arranged in some special situations
• As the macula serves the most important
vision 90% of the axons of the NFL come from
this region and form papillo-macular bundle
• The temporal fibers follow an arcuate course
around macula
• Nasal axons pursue a radial course
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118. 10) Inner limiting membrane
• This is the layer adjacent to the vitreous
• This is formed by the basal lamina of the Muller
cell footplates
• Its inner surface-vitreal- is smooth and the outer
surface is uneven
• This is a thin membrane of about 1887 nm
posteriorly and only around 306 nm in the
equator
• It is very thin in the foveola or is attenuated and
is absent over the major retinal vessels and ONH
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Has Henle’s layer
in inner half

120. Blood supply of Retina
The retina has dual blood supply
• Its outer retina including the photoreceptors, ONL,
outer plexiform layer-OPL are avascular.
• Their nutritional needs supplied by diffusion of
materials from choriocapillaris or RPE transport from
choriocapillaris
• The inner retina is vascularized from RNFL to the INL
• The capillaries of retinal vessels have tight endothelial
junctions which prevent escape of large molecules in to
extracellular space of retina –inner retinal barrier
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121. Blood supply of the retina
• The blood supply of the inner retina is from
Central retinal artery which is a branch of
ophthalmic artery
• CRA enters the Optic nerve one cm behind the
globe and occupies the central portion of ON
• CRA as it enters the retina –ONH –divides in to
two branches- upper and lower branches
• The upper and lower branches in turn divide in to
temporal and nasal branches
• The major vessels lie in the NFL very near to the
ILM
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Blood supply of retina
Three layers of capillary network from the CRA
Radial peripapillary capillaries (RPCs) supply the RNFL-supply
retina near the ONH for a few mm only
The inner capillary –superfical-network lie in the ganglion
cell layers under and parallel to the RPCs- supply ganglion
cells and RNFL
The outer capillary network - IPL, Inner nuclear layer AND
inner part of OPL
The retinal arterial circulation is endarterial
so any closure leads to damage to that part of the retina

123. Retina-blood supply OF FOVEA
• There is a ring of blood vessels around the
foveola that surround a capillary-free zone 450-
600 microns in diameter
• The macular vessels arise from branches of the
superior temporal and inferotemporal arteries
• At the border of the avascular zone the capillaries
become two layered and finally join as a single
layered ring
• The collecting venules are more deep (posterior)
to the arterioles and drain blood flow back into
the main veins
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124. FAZ
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126. Outer retinal supply
• Choriocapillaris supplies the outer retina
• Choriocapillaris is part of choroid and is
supplied by short ciliary arteries and long
ciliary arteries
• Venous drainage is by vortex veins
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128. Choroidal blood supply of retina
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129. Macula –posterior pole which vessel is
this?
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