anatomy of the 10 LAYERS of retina

1. Development &
anatomy of retina.
Dr. Nikita Jaiswal
Resident 1st year

2. GLOSSARY:
--INTRODUCTION
--DEVELOPMENT
--TOPOGRAPHY
--LAYERS

3. RETINA :
US:ret.e.n∂
UK:ret.I.n∂
It is derived from a latin word rete=net
It is the innermost tunic of the eyeball
Thin,delicate & transparent membrane

4. DEVELOPMENT:
Optic cup
Outer wall
Retinal
pigment
epithelium
Inner wall
Neurosensory
retina

5. RPE:
Origin: cells of outer wall of optic cup
Start: around 6th wk of gestation
specific: posterior part forms RPE
comprises: initially mitotically active pseudostratified col
ciliated epith---melanogenesis starts---cilia disappears
this mitotic activity ceases by birth
final modelling: finally growth of the eye & RPE itself
accommodated by hypertrophy of existing cells
shape: hexagonal
size: homogenous

6. Neurosensory retina:
origin:inner wall of optic cup—single layered epithelium
epithelium-- with an internal & external basement membrane.
Gestational clock:
4th-5th week: the primitive retina arranged in 2 zones
outer primitive zone –filled with 8-9 rows of nuclei
inner marginal zone– devoid of nuclei
6th- 7th week : neuroepithelial cells divide by mitosis
Inner neuroblastic:--ganglion cells, muller’s cells,amacrine cells
Outer neuroblastic:--rods & cones,bipolar cells,horizontal cells.
(This is separated by transient fibre layer of
CHIEVITZ)

7. At 10.5 wks: Zone where the process of cells from the inner
neuroblastic layer intermingle(Inner plexiform layer).
Outer nuclear layer: this is formed by the remaining components
of outer neuroblastic layer.
External limiting membrane:It is identifiable in the early stages
as rows of tight junctions.
DIFFERENTIATION STARTS BY 6th WK.
Recognizable by 5.5 months
macula: delayed upo to 8 months of gestation.

8. 4TH -5TH
WEEK
6TH-8TH WEEK
10TH-12TH
WEEK
4TH MONTH

9. TOPOGRAPHY :-
• Retina proper is- thin
-delicate layer of nervous tissue
-- surface area of 266 mm2
LANDMARKS: 1. optic disc
2.area centralis
3.the peripheral retina : (equator+ora serrata)
4. retinal blood vessel
Retina is thickest near the optic disc (0.56 mm )
thinner towards periphery
equator—0.18 mm, ora serrata– 0.1mm

10. The OPTIC DISC:-
SHAPE: circular to oval
SIZE: 1.5 mm in diameter
CENTRALLY: a depression k/as
physiological cup
Size depends on:
--course of OPTIC NERVE
--glial & connective tissue
--anatomical arrangement of retinal &
choroidal vessels.

11. AREA CENTRALIS
• FOVEA :
PARAFOVEAL(0.5mm)
PERIFOVEAL(1.5mm)
• FOVEOLA
• LOCATION: post.fundus temporal to
Optic disc
• SHAPE:elliptical horizontally
• SIZE:5.5 mm & corresponds to 15’ of
visual field
• Function: adapted for diurnal variation
& colour discrimination.

12. THE FOVEA
• Approx the center of the area centralis
• 4 mm temporal to the O.D
• 1.85 mm in diameter & corresponds to
5’ visual field
• 0.25mm in thickness
• At the center the layers thinned out –
central concave indentation—
foveola—downward sloping border
which meets the floor of foveal pit
k/as clivus.
THE FOVEOLA
• 0.35 mm in diameter
• 0.13mm in thickness
• Area of highest VA
• Appears deep red in colour than
the adjacent retina because of rich
choroidal circulation
• Colour appears cherry red spot.

13. THE MACULA LUTEA
• SHAPE& COLOUR-- oval zone of
yellow colouration within the
central retina
• The yellow colour is derived from
the presence of the carotenoid
pigment,xanthophyll in the
ganglion & bipolar cells.

15. Peripheral retina:Increases the field of vision
• Near periphery: 1.5 mm around the
area centralis.
• Mid periphery:3 mm around the
near periphery.
• Far periphery:in the horizontal
meridian this region xtends 9-10
mm on the temporal side 16 mm on
the nasal side from the O.D.
• ORA SERRATA:- most anterior region of
the retina,consist of dentate fringe,which
denotes the termination of retina.
• 2.1 mm wide temporally
• 0.7-0.8 mm wide nasally
• From the limbus:6.0 mm nasally
7.0 mm temporally

16. LAYERS:
1.Retinal pigment epithelium
2.layer of rods & cones
3.external limiting membrane
4.outer nuclear layer
5.outer plexiform layer
6.inner nuclear layer
7.inner plexiform layer
8.ganglion cell layer
9.nerve fibre layer
10.internal limiting membrane

17. RPE: RETINAL PIGMENT EPITHELIUM
It is to be a continuous brown sheet from optic nerve to the ora serrata.
Grossly more pigmented in the macular region than ora serrata.
Structure: single layer of approx. 5 million cells firmly attached to its basal
lamina.
Size & shape: 4-8 sides & give the appearance of cobblestones,hexagonal
total no from 4.2 to 6.1 million.
Area centralis:12-18µm width & 10-14 µm height.
RPE is attached firmly to bruch’s membrane &loosely attached to layer of
rods & cones.

18. FUNCTIONS OF RPE….
• Important role in photoreceptor
renewal & recycling of vit A.
• It transport nutrients &
metabolites trough the blood
retinal barrier.
• RPE have a phagocytic action.
• These cells provides mechanical
support.
• They manufacture pigment which
presumably has an optical
function.
• Rods shed disc at dawn
• Cones shed at dusk
• Melanin granules: spindle shaped
1 µm in diameter & 2-3 µm long
are abundant at the apex of RPE
• Dihydroxyphenylalanine---
melanin (tyrosinase)

19. BRUCH MEMBRANE:
The basal portion of RPE is attached
to it
which has 4-5 layers
inner to outer:
--BM of the RPE(0.3µ)
--Inner collagenous layer(1.5µ)
--middle layer of elastic fibres(0.8µ)
--outer collagenous layer(0.7µ)
--BM of the endothelium of the
choriocapillaries(0.1µ)

20. LAYER OF “RODS & CONES”(PHOTORECEPTORS): These are the end organs
of vision which transform light energy into visual impulse.
Rods :betw 77.9& 107.3 million
Avg 92 million
Rod free area at the fovea is
0.35mm which is 1.25’ VF
Nasal retina has 20-25%
visual pigments give scotopic
vision.
Cones :betw 4.08 to 5.29 million
Avg 4.6 million
Its density is max. at fovea 199000
mm2
Nasal retin ahas 40-45%
Visual pigments give photopic
vision & colour vision.

21. Structure of photoreceptors:
• Rod: 40-60 µm long
• Outer segment:cylindrical,disc stacked one on other
n.o of disc varies 600-1000/ rod,22.5-24.5nm in thkn
• Inner segment:thicker than the outer segment
Ellipsoid:is adjacent to its OS & contains abundant
n.o of mitochondria
Myoid: contains glycogen
• outer rod fibre: arises from inner end of rod,which
passes through ELM--swells into nucleus –rod
granule(ONL)—terminates as inner rod fibre(OML)

22. Structure of photoreceptors:
• Cones:40-80µm long largest at fovea nd
shortest at periphery
• Outer segment : conical, iodopsin,discs are
narrower 1000-1200discs/cone
• Inner sgment : it is the same as rods only the
ellipsoid is more plump nd contains more
mitochondria.
• Inner segment: directly continues with its
nucleus & lies in ONL, --a stout cone fibre
runs from the nucleus at its end provided
with cone foot (OPL)

23. EXTERNAL LIMITING MEMBRANE:
• Appearance : fenestrated membrane from OS to the edge of OD
through this passes the processes of the rods & cones
electron micro: ELM is formed by junction between the cell memb of photoreceptors nd
muller’s cell.
THIS IS NOT A BASEMENT MEMBRANE.
OUTER NUCLEAR LAYER
Primarily formed by the nuclei of rods & cones
Cone nuclei(6-7µm) rod nuclei(5.5µm)---lie in a single layer next to ELM
Rod nuclei forms the bulk xcept in the foveal region
It varies at places
Nasal to disc: 45µm thick ,8-9 layers of nuclei
Temporal to disc: 22 µm thick , 4 rows of nuclei
Foveal region :50 µm , 10 rows of nuclei

24. OUTER PLEXIFORM
LAYER:A.K.A Henle’s layer
Thickest at macula 51µm.
Mainly consist of oblique fibres that
have deviated from fovea
contains;synapses of rod spherules &
cone pedicles
This layer marks the junction of th
end organs of vision & first order
neurons of retina.

25. Inner nuclear layer:
resembles: outer nuclear layer
absent : at fovea
contents: bipolar cells,horizontal cells,amacrine
cells,soma of mullers cells,capillaries of central retinal
vessels.

26. Bipolar cells
• Neurons of first order of vision.
• Consist: entirely nucleus & in the
INL.
• Dendrites arborize with the rod
spherules & cone pedicles in the
OPL their axons arborize with the
dendrites of ganglionin the IPL.
• Nine types of bipolar cells.
Amacrine cells
• Situation: at the innermost part of
INlayer
• Shape:piriform body & a single
process which passes to IPL.
• Forms connection with axons of
bipolar cells & the dendrites &
soma of the cells.

27. Muller’s cell:
location: nucleus & cell bodies in the inner nuclear layer.
Outer ends:extend to ext. limiting memb.
Inner ends: reach up to the int. limiting memb.
Function: structural support & contribute to the metabolism of
the sensory retina.

28. Inner plexiform layer
• Layer consists of synapses between
the axons of bipolar cells (1st order
neurons)
• Mullers cell are present in this
• This layer is absent at the foveola.
Ganglion cell layer
• The cell bodies & the nuclei lie in this
layer(2nd order neuron)
• This layer is composed of a single row of
cells xcept at macular region where it is
multi-layered & on the temporal side it
is 2 layered.
• This layer is absent in foveola.

29. Nerve fibre Layer
• Layer consist of the unmyelinated
axons of the ganglion cells which
converge at ONH.
• Passes through lamina cribrosa&
become ensheathed by myelin
post to lamina.
Internal limiting membrane
• This is true basement membrane.
• The fibrils of vitreous merge with
internal lamellae of this layer.
• It consists of 4 elements:
• Collagen fibrils
• Proteoglycans
• Basement membrane
• Plasma memebrane of the muller
cells& possibly other glial cells

30. BLOOD RETINAL BARRIER
• INNER & OUTER TYPE
• FUNC: TO MAINTAIN RETINAL HOSTATIS
• OUTER BRB: AT RPE FROM CHOROID TO THE SUB RETINAL SPACE
INNER BBB:INNER REINAL MICROVASCULATURE
• THE FREE FLOW OF FLOW OF FLUIDS & SOLUTES ARE PROHIBITED FROM THE
VASCULAR LUMEN INTO THE REINAL INTERSTITIUM.
• THE ENDO. CELLS ARE CLOSELY BOUND TOGETHER ABOUT THE LUMEN BY
INTERCELLULAR JUNCTIONS OF ZONA OCCLUDENS TYPE.

31. THANK YOU
HAVE A GREAT DAY