ANATOMY OF RETINA - (Basics)

1. ANATOMY OF RETINA

2. • The Retina is the
innermost tunic of the
eyeball which is a thin,
delicate and transparent
membrane and is the most
highly developed tissue of
the eyeball.

3. GROSS ANAT. OF RETINA
• Extent : From the optic disc to the
ora serrata
• Surface area : 266 mm2
• Thickness : At posterior pole 0.56mm
At the ora serrata 0.1mm
• Colour : Purplish red
(visual rhodopsin)
• Regions : 3 distinct regions
 Optic disc
 Macula Lutea
 Peripheral retina(General fundus)
TO ADD PICTURE

4. OPTIC DISC
• 1.5 mm diameter, well defined circular
area
• Appears pale (pale pink) due to lamina
cribrosa and absence of vasculature
• Physiological Cup: Depression seen in
it , central retinal vessels emerge
through the Centre of this cup.
• At the optic disc- All retinal layers
terminate except nerve fibres , which
pass through the lamina cribrosa to run
into optic nerve.

5. MACULA LUTEA (Area Centralis)
• About 5.5mm, temporal to theoptic disc
betweenthetemporal vascular arcades.
• Yellowcolour due to presence of the
oxygenated carotenoid (Zeaxanthine and
Lutein) pigment.
• Approx. 15 degree visual field, Photopic and
colour vision primarily
• Macular regiondivisible into
FOVEOLA
FOVEA
PARA FOVEOLAR ZONE
PERI FOVEOLAR ZONE

6. FOVEA
• Concave central retinal depression at Posterior pole
of globe.
• Diameter-1. 5mm –5 degrees of visual field
• Cones only
FOVEOLA
• central floor of the fovea where INNER NUCLEAR
and GANGLION LAYER are absent
• 0.35mm in diameter and 0.15mm in thickness
UMBO ( LIGHT REFLEX)
• Tiny depression seen in the Centre of foveola viz
referred to as the central bouquet of cones (150 to
200 micrometer) due to greatest concentration of
cones.

7. FOVEAL AVASCULAR ZONE
• Is located inside the fovea but outside the foveola.
• 0.3TO 0.6 mm
• Important in FA to identify Fovea Centre
PARAFOVEA
• Refers to a belt that measures 0.5mm in width which
surrounds the margin of fovea.
• This include 4-6 layers of ganglion cell and 7-10 layers of
bipolar cells.
PERIFOVEA
• Refers to a belt which measures 1.5mm in width and
surrounds the parafoveal area.
• This include several layers of ganglion cells and Six layers of
bipolar cells.

8. PERIPHERAL RETINA
• Increases the field of vision
• Divided into 4 regions
 NEAR PERIPHERY-1.5mm around area centralis
 MID PERIPHERY- 3mm wide zone around near
periphery till equator
 FAR PERIPHERY- from optic disc- 9-10 mm on
temporal side and 16 mm on nasal side , from
equator till ora serrata
 EXTREME PERIPHERY -Ora serrata and pars plana

9. MICROSCOPIC RETINA

10. RETINAL PIGMENT EPITHELIUM
• Outermost layer of the retina.
• Consists of single layer of hexagonal
shaped cells containing pigment
• It is thickly adherent to the underlying
Bruch's membrane and loosely to the
layer of rods and cones of the retina.
• The space between RPE and the sensory
retina is called subretinal space.
• Separation of the RPE from sensory
retina is called retinal detachment and
the fluid between the two layers is called
Sub retinal fluid (SRF).

11. • RPE cells are connected to each other by tight
junctions i.e. zonulae occludents and zonulae
adherents. Forming the outer blood retinal barrier.
• Apical part – containing microvilli towards rods and
cones along with MELANIN and LIPOFUSCIN pigments
• Basal part – towards Bruch's membrane containing
infoldings to increase surface area
• FUNCTIONS
 Recycling of vitamin A.
 Maintains the integrity of sub retinal space.
 Transport of nutrients and metabolites.
 Phagocytosis of photoreceptors.
 Manufactures pigment.
 Regeneration and repairing after injury.

12. LAYER OF RODS AND CONES (Neuro epithelium)
• Rods and cones (photo receptors) , end organs of vision , transform
light energy into nerve impulses.
• Rods contain photosensitive substance Rhodopsin whereas cones
contain Idopsin
• Cone cells – Photopic and central vision , Rod cells - Scotopic vision and
peripheral
• Cones = 6.5M , Rods = 120M
• At fovea maximum cones are present and rods are absent.

13. STRUCTUREOF PHOTORECEPTORS

14. STRUCTURE OF ROD CELL
• Length = 40-60µm
• Outer segment is cylindrical , contains Rhodopsin & composed
of numerous protein lamellar disc.(600-1000/rod)
• Disc contain 90°/o of visual purple.
• Outer segment is attached to inner via cilium.
• Inner segment is thicker and has regions as
Outer - Ellipsoid ( mitochondria)
Inner - Myoid (organelles)
• Outer rod fibres- from inner segment at EXTERNAL.L.M,
swells into nucleus (rod granule) at the OUTER.NUC.L
and ends as Inner rod fibre as rod spherule at OUT.PLEX.L

15. STRUCTURE OF CONE CELL
•Length = 40-8Oµm
•Outer segment is conical viz shorter than
rod.
•Contains Iodopsin pigment packed in
lamellar disc.(1000-1200 disc/cone)
•Inner segment & cilium are similar to rods.,
But contain many mitochondria and end as
lateral processes called CONE FOOT at
OUTER.PLEX.L

16. EXTERNAL LIMITING MEMBRANE
• Fenestrated membrane extending from the ora serrata up to
the edge of optic disc. ( then as basal lamina between
pigmented and non pigmented epithelium of ciliary body)
• Processes of rods and cones pass through it.
• This layer is formed by the junction between the cell
membrane of photoreceptors & muller cells.( not a true
basement membrane)

17. • OUTER NUCLEAR LAYER
• OUTER PLEXIFORM LAYER

18. OUTER NUCLEAR LAYER
• Made up of the nuclei of rods & cones.
• Cones nuclei - 6-7µm , Rod nuclei -
5.5µm , nuclei lie in a single layer next
to the E.L.M.
• Rod nuclei form the bulk of this layer
except at the cone dominated foveal
region. ( 10 layers)
• Stain with Mallory stain
Cones- red , rods – orange

19. OUTER PLEXIFORM LAYER
• Synapses between rod spherules
and cone pedicles with dendrites of
bipolar cells and processes of
horizontal cells
• Marks the junction of end organs of
vision and 1st order neurons in
retina.
• Thickest at macula 51 µm consists of
predominantly of oblique fibres that
have deviated from fovea also
known as HENLE’S LAYER.

20. Outermost Layer- Horizontal
Cell Nuclei
Outer Intermediate
Layer- Bipolar Cell nuclei
Inner Intermediate Layer-
Muller nuclei
Innermost Layer-
Amacrine and inter plexiform
nuclei
INNER NUCLEAR LAYER

21. • Contribute to vertical
communication
within the retinal
layer.
• Carry out
paracrine
functions.
• As principal glial cells, act as a
supportive framework and a
nutritive function.
• Astrocytes (mc around vessels),
oligo
And microglia
• Synapses with the
processes of Amacrine
cells and cell bodies of
the diffuse ganglion
cells.
• Neuronal interconnections
between photoreceptors
and bipolar cells .
• A cells with Cones
• B cells with Rods
Horizont
al
cells
Bipola
r
cells
Amacrin
e
cells
Müller
cells
Neurons of First Order

22. BIPOLARCELLS
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
Innervate more than one cone
pedicle

23. INNER PLEXIFORM LAYER
• Synapses between Axons of bipolar cells
(1st order neurons) and Ganglion cells ( 2nd
order neurons)
• Amacrine cells also mediate
interactions within the layer and the
interplexiform cells receive input
from the Amacrine cells
• Also contains processes of Muller
cells , abundant microvasculature
, occasional displaced nucleus of
a ganglion / Amacrine cells.
• Layer is absent at foveola

24. GANGLION CELL LAYER
• Mainly composed of cell bodies 2nd order neurons of visual pathway
• Others: Processes of Müller cells, other neuroglia, branches of retinal
vessels are also present.
• At foveola and optic nerve head, ganglion cell layer is absent.
• Near foveola 6-8 layers, temporal side of optic disc 2 layers and at periphery
single layer
• TYPES W,X,Y ganglion
Off center & on center cell
MONOSYNAPTIC (central) & POLYSYNAPTIC CELL (peripheral retina)
1.2 million ganglion
cells at retina
Each produce a
single axon
Converge and exit
from the eye as
OPTIC NERVE
Synapse with cells of LGB , 3rd order neurons

25. NERVE FIBRE LAYER (stratus opticum)
• Formedbythe axons of the ganglion cells
• Theydonot become myelinateduntiltheypass through the lamina
cribrosa
• The myelinsheath beingformedbythe oligodendrocytes
• Also has centrifugal fibres, muller cells processes, retinal vessels and neuro
glial cells – macro ( structure) and microglia (wandering histiocytes)
 ARRANGEMENT OF NERVE FIBRE IN RETINA
1. Nasal Half: Directly to optic disc as superior and inferior radiating
fibres (Srf & Irf).
2. Macular region: Pass straight in temporal part of disc as
papillomacular bundle.(PMB)
3. Temporal retina: Arch above and below the macular/ as superior /
inferior arcuate fibres. (Saf & Iaf).

26. INTERNAL LIMITING MEMBRANE
• Pas positive true basement membrane.
• Forms interface between retina and vitreous.
• Consists of elements:
Processes of Müller cells and other glial cells
Collagen fibrils
Proteoglycans
Basement membrane

27. BLOOD SUPPLY
• Outer four layers – Choriocapillaris
• Inner six layers- Central retina Artery
• Retina is supplied by Central RetinalArtery, Enters optic nerve on lower
surface 15-20 mm behind the globe.
• At the optic disc divide as sup and inf branches – nasal and temporal
• Retinal arteries are end arteries and have no anastomosis at ora
serrata.
• Fovea is avascular but partially gets blood supply from choriocapillaris.
• Macular area gets blood supply from central retinal artery .

28. • Superficial capillary network lies at the nerve fibre layer
• Deep network lies between inner nuclear and outer
plexiform layer – more dense
• BLOOD RETINAL BARRIER
• The endothelial cells of retinal capillaries are closely bound
together (zona occludens type) and form Blood Retinal
Barrier – absence of fluorescence leakage
• The endothelial cells lined by basement membrane around
which there are pericytes. Pericytes also have basement
membrane
• Ratio of endo : pericytes is 1:1

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