Retina : an overview Seminar Presentation include Anatomy, Physiology, Pathology, Medical management and surgical management of retinal diseases and also latest updates. The Seminar was written and posted by famous ophthalmologist-- Dr Niraj Kumar Yadav MBBS, MS Ophthalmology FICM, FID, NDEP Liverpool UK

1. Anatomy of retina
Dr Niraj Yadav

2. Presentation layout
 Introduction
 Embryology
 Topography & Major landmarks
 Anatomy & Functions of different retinal layers
 Clinical significance

3. Introduction
• Rete in Latin : Net
• It is innermost Thin,
transparent layer of
nervous tissue of the
eye
• Extends from optic disc
to ora serrata

4. Embryology of Retina
• Retina develops from neuroectoderm
(3rd week ofgestation)
shows linear thickening on
either side that gets depressed
Neural plate
Optic sulcus
deepens to form
Optic vesicle

5. Optic vesicle
( 4th wk )
invaginates
Optic cup

7. (4-5th wks)
Optic cup
Outer wall
Pigment
epithelial
cells
Retinal pigment
epithelium
Basement
membrane
Bruch’s
membrane
Inner wall

8. Inner
neuroblastic
layer
Ganglion
cells
Amacrine
cells
Muller
cells
Nerve
fibre
layer
Ganglion
cell layer
Inner
plexiform
layer
Outer
neuroblastic
layer
Horizontal
cells
Bipolar cells
Rods &
cones
Inner
nuclear
layer
Outer
plexiform
layer
Outer
nuclear
layer
Layers
Of Rods
& cones
(6-12th wks)
(12-28th wks)
(12-28th wks)

9. Development of Macula
• Differentiation of the
photoreceptor cell occurs early
in macula.
• Foveal pit :7 months of
gestation
• Diameter of cones decreases
and there is continuous
migration of cones towards the
foveal pit
• Remodeling occurs till 4 years
of age

10. TOPOGRAPHY OF RETINA
• Has a surface area of about
266 mm²
• Thickest near the optic disc
(0.56mm)
• Thinner towards the periphery
(0.18mm at equator and
0.1mm at ora serrata)

11. MAJOR LANDMARKS OF RETINA
• Optic disc
• Area centralis
(including fovea and
foveola)
• Peripheral retina
• Ora serrata
• Retinal blood vessels

12. Optic disc
• Pink well defined , round to
oval
• 1.5 mm in diameter
• All the retinal layers
terminate (except nerve fiber
layer )
• Physiological cup : central
retinal blood vessels emerges
through the centre of the cup
.

13. Area Centralis
• Located in the posterior pole
and contains 2 or more
ganglion cell layer.
• Located Temporal to disc
• Between arcuate and
temporal retinal vessels
• It is Elliptical in shape
• 5.5 mm in diameter
• Corresponds to 15 degree of
visual field

14. Fovea
• Lies in the centre of area
centralis
• 4 mm temporal to the disc and
0.8 mm below the horizontal
meridian
• 1.85 mm in diameter
• 0.25 mm in thickness
• corresponds to 5 degree of
visual field

15. Foveola
• 0.35 mm in diameter and
0.13 mm in thickness
• Represents only 1.25
degree of visual field
• Highest visual acuity
• Umbo : Corresponds the
foveolar reflex

16. Foveal avascular zone
• It is the capillary free zone in
the center of fovea
• Diameter is variable 0.25mm-
0.6mm
• It is important land mark in
fluorescein angiography to
localize the center of fovea

17. Peripheral retina
It is divided in four regions
• Near periphery : 1.5 mm around the area centralis
• Mid periphery : 3 mm around near periphery
• Far periphery : extends from optic disc , 9-10 mm
temporally and 16 mm nasally
• Ora serrata : it is the serrated peripheral margin
where the retina ends and cilliary body starts

18. Ora serrata
• Dentate process : teeth like
extensions
• At ora ,sensory retina is firmly
attached to vitreous and retinal
pigment epithelium
• Its distance from the limbus is 6
mm nasally and 7 mm
temporally
• 2.1 mm wide temporally and 0.7
-0.8 mm wide nasally
• Located 6-8 mm away from
equator and 25 mm away from
the optic nerve on the nasal side

19. Layers of retina
 Retinal pigment epithelium
 Layers of rods and cones
 External limiting membrane
 Outer nuclear layer
 Outer plexiform layer
 Inner nuclear layer
 Inner plexiform layer
 Ganglion cell layer
 Nerve fibre layer
 Internal limiting membrane

20. Retinal pigment epithelium [RPE]
1. Outer most layer consists of single layer of hexagonal shape cells
which contain pigment.
2. It is firmly attached to underlying Bruch’s membrane and loosely attached to
layer of rods and cones.
3. Space between RPE and sensory retina is called sub retinal space. Separation
of RPE from sensoryretina is called retinal detachment.
4. On electron microscopy the adjacent RPE cells are connected with each other
by tight junctions and constitute the outer blood retinal barrier. –Terminal
bars.
5. Terminal bars- ( Gap junctons , zonula ocludens and zonula adherens.
6. Zonula ocludens forms the external component of the Blood retinal Barrier.
7. Rest of intercellular space is filled by Extra cellular matrix-VERHOEFF’S
MEMBRANE in light microscope

21. .
 RPE cells at fovea are taller, thinner and contains more and
larger pigment granules than elsewhere in fundus, thereby
giving dark colour to this area.
RPE cells in cross section can be differentiated into apical
and basal configurations.

22.  contains multiple round and ovoid pigment
granules :- 1)melanosomes (apex)
This melanin absorb stray light and
minimize scatter
2) Lipofuscin granules :- arise from outer
segment of photoreceptor, represent
residual bodies from phagosomal activity
Aka wear and tear pigment

23. 3) Phagosome = membrane enclosed
packets of disc outer segments engulfed
by RPE
4) Mitochondria = aerobic metabolism
5) RER
6) Golgi apparatus

24. PDGF- cell growth and healing
VEGF- stimulate normal or pathologic
neovascular growth
TGF- moderates inflammation
PEDF- neuroprotectant

25. Function of the RPE
 Absorption of scattered light
 Blood retinal barrier function
 Visual pigment regeneration and synthesis
 Synthesis of growth factors
 Maintenance of retinal adhesion
 Phagocytosis
 Electrical homeostasis
 Repair and regeneration after injury

26. Composed of 3 element
 Neuronal element
Glial element
Vascular element

27. Photoreceptor layer - Rods and cones
Average 110-125 million rods and 6.3-6.8
million cones
Consist- outer and inner segment
Outer segments- surrounded by
mucopolysaccharide matrix and make
contact with RPE
Inner segment- thicker than outer segment
and consist of two regions:
ellipsoid(abundant mitochondria) and myoid

28.  Rod outer segment – cylindrical, multiple laminated
disc (600-1000) resembling stack of coin and cilium
(connects outer and inner segments)
 Microtubules of cilium have 9 plus 0 cross-sectional
configuration (nonmotile)
 Inner segment – a) outer eosinopilic ellipsoid –
mitochondria
b) inner basophilic myoid-
glycogen and ribosome (protein synthesis)
 Inner portion of cell consist of spherule formed by
single invagination accommodating 2 horizontal cell
process and 1 or more central bipolar process

30. Outer segments have different morphology
depending on location on retina
Extrafoveal cone have short conical
ellipsoids and myoids and nucleus tends to
be closer to ELM
Foveal cone have longer cylindrical inner
segments
Cones outer segment have more disc
(1000- 1200) & attached to each other
Intradisc and interdisc space are wider

31. Cone inner segments: at fovea are long
and tapered but at periphery are conical
Ellipsoid part - more mitochondria (200-
300 per cells)
Unlike rod inner segment is directly
continuous with its nucleus
Cone pedicle synapse with other rods,
cones, horizontal and bipolar cells
process.

32. TYPES OF CONES
• L-cone: responds most to light of
long wavelengths, peaking in the
yellow region(560nm)
 M-cone: responds most to light
of medium-wavelength, peaking
at green(530nm)
• S-cone: responds most to short-
wavelength, peaking at violet
color(430nm)s

33. 3 classes of cones: red, green, blue
(sensitive at 560, 530 and 430nm)
Gene for cone is in X chromosome.
Color blindess more common in males
Rods contains visual purple(rhodopsin) and
responsible for peripheral vision and scotopic
vision.
Cones are responsible for central
vision(photopic vision) and colour vision

34. Highest density of cones is at fovea
Number of cones falls off rapidly outside
fovea
Cones are greater on nasal and inferior
Rods are absent at fovea but present in
large number in ring-shaped zone 5-6mm
from fovea

35. • Night (scotopic)
vision - rod
photoreceptors
• Daylight (photopic)
vision - cone
photoreceptors
• Twilight (mesopic)
vision - combination
of cones and rods
Functions: Rods and Cones

36. Bipolar cells:-
Bipolar cells are oriented vertically, axons
synapse with rods and cones forming outer
plexiform layer and with axons of ganglionc
cells and amacrine cell forming inner
plexiform layer
Form 1st order neuron

37. • On the basis of morphology and synaptic
relationship there are 9 types of bipolar cells-
1. Rod bipolar cells
2. Invaginating midget bipolar cells
3. Flat midget bipolar cells
4. Flat diffuse bipolar cells
5. Invaginating diffuse bipolar cells
6. ON- center blue cone bipolar cells
7. OFF- center blue cone bipolar cells
8. Giant bistraitified
9. Giant diffuse invaginating.

38. Ganglion cells:-
Axons of ganglion cells bend to become
parallel to retina forming nerve fiber layer.
 Ganglion cell forms second order
neuron(nerve cells of LGB -3rd order)
 Nerve fiber from temporal retina follow
arcuate around macula entering sup and inf
pole of optic disc
 Visibility of nerve fiber is enhanced using
green illumination

39.  Muller cells – extend vertically from ELM to
ILM
 Nuclei located in INL
Fx :- a)structural support, nutrition to retina
b)insulin and GF produced by muller
cells helps in metabolism of sensory retina
c) degradation of glutamate and GABA
d) mRNA for CA II – bufferingCO2
liberated into extracellular space by
neurosensory retina
 Contains :- retinaldehyde binding protein,
glutamine, taurine

40. MULLER CELLS
• Inner half cells contain rough and smooth ER, golgi
apparatus, mitochondria free ribosomes
protein synthesis.
• Outer half of cells adapted to absorption and intracellular
transport.
• Important role in orientation, displacement and
positioning of developing neurons.
• Acts as principle glial cells of retina
conserve structural alignment of neuronal
elements.
• Also produce retinaldehyde binding proteins for retinal
metabolism.

41. Amacrine cells
• Soma are flask or urn shaped with diameter of 12 micron.
• Has single process but branches extensively.
• Nucleus is round and has prominent infoldings
• Most Amacrine cells have GABA(gamma-aminobutyric acid)
and glycine as neurotransmitters having inhibitory action on
ganglion cells.

42. Astrocytes
Microglia
Oligodendrocytes

43. BLOOD SUPPLY OF THE RETINA:
•Outer 4 layers of retina is supplied by (till outer nuclear layer)
choriocapillaries.
•The inner six layers gets its supply from central retinal artery which
is a branch of ophthalmic artery.
•The outer plexiform layer gets partly by both the above arteries.
•The fovea is avascular and is mainly supplied by choriocapillaries.
•The inner portion of the retina is perfused by branches of the central
retinal artery.
•In 30% of eyes ,a cilioretinal artery,branching from the ciliary
circulation ,supplies part of inner retina mainly The Macula Region.
•The retinal blood vessels maintain the inner blood-retinal barrier.This
of non-fenestrated
physiological barrier is
endothelial cells,whose
due to single layer
tight junctions are impervious to tracer
substances such as fluorescein.

44. Retinal capillaries
Two capillary networks :
 Superficial – lies at the level of
nerve fibre layer
between inner
outer plexiform
 Deep – lies
nuclear and
layer

45. Blood-Retinal Barrier
• Outer – tight junction between RPE
cells.
• Inner – endothelial cells of retinal
capillaries are bound closely by
intercellular junction of zonula
occludens - thus prohibiting free flow
of fluid and solutes.
• These endothelial cells are encircled
by basement membrane around is a
layer of pericytes.

46. •Retinal blood vessels lack an internal elastic lamina & a
continuous layer of smooth muscle cells.
•The retinal arteries
anastomoses.The only
are end arteries & have no
place where the retinal system
anastomoses is in the neighbourhood of lamina cribrosa.
•The veins of the retina unite to form Central retinal vein at the
disc, which follows the corresponding artery.
•The terminal fundus arterioles bend sharply and dip almost
vertically into the retina.
•In most of the Extramacular fundus- two retianal capillary
networks- a superficial and a deep.
•In parafoveal zone it is well developed and in 3 layers.
•A capillary free zone of 500micro metre diameter in foveal
zone- FAZ.[foveal avascular zone]

47. First branch of ophthalmic artery
Arises near optic foramen and course as
follows:
Outside optic nerve: runs a wavy course
forward below optic nerve, inferomedial
aspect of nerve it bends upwards to pierce
dura and arachnoid.
In subarachnoid space: it bends upwards
and invaginates pia reaching centre of
nerve (surrounded by sympathetic nerve-
nerve of Tiedemann)

48. In centre of optic nerve: bends forwards
and with vein lie in temporal side, pierces
lamina cribosa and appear in eye
In optic nerve head: lies superficial nasal
of cup and divides into 2 branches superior
and inferior which subdivides into temporal
and nasal branch near margin

49. Accompanies retinal artery
Diameter 1/3rd larger than artery
Artery tends to lie superficial to vein thus
tend to cross superficial to the vein
Drains to cavernous sinus or superior
ophthalmic vein

50. 1. ELM- outermost layer, not a true
membrane, formed by attachment sites of
adjacent photoreceptors and muller cells,
highly fenestrated
ONL- nuclei of cones and rods
(cones>rods).
Nasal to disc: 8-9 layers of nuclei
Temporal to disc: 4 rows
Fovea: 10 rows
Rest of retina except ora serata: 1 cone
nuclei and 4 rods

51. OPL-synapse between rod spherules,cone
pedicles with dendrite of bipolar and
horizontal cells. Thickest at macula and
contains more fibers and more oblique as
they deviate from fovea (henle fiber layer)
INL- nuclei of Bipolar, muller, horizontal,
amacrine cells

52. IPL- axons of bipolar and amacrine cells
and dendrites of ganglion cells
absent at foveola
GCL- cell bodies and nuclei of GC lies in this
layer(second order neuron of visual
pathway) Absent at foveola.
Throughout retina single row of cells [except
macula 6-8 layers and on temporal side 2
layers.
NFL or stratum opticum- formed of axons of
ganglion cells, unmyelinated, 0.5-2micm,
converge at optic nerve head, pass
through lamina cribrosa.
It also contains: Centrifugal nerve fiber
Muller processes, Neuroglial cells

53. Internal limiting membrane
– It is basement membrane that forms theinterface
between the retina and vitreous.
• It consists of four elements:
–Collagen fibrils
– Proteoglycans (mostlyhyaluronic acid)
–Basement membrane
–Plasma membrane of Muller cell.
•It is thickest at the fovea but absent at edge of optic
disc.

54. 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 disck as
papillomacular bundle (pmb).
3. Fibres from the temporal retina
arch above and below the
macular and papillomacular
bundle as superior and inferior
arcuate fibres (saf and iaf) with
a horizontal raphe in between.

55. Arrangement of nerve fibres of optic nerve head
 Fibres from the peripheral
part of retina lie deep in
retina but occupy the most
peripheral (superficial) part
of optic disc
 Fibres closer to optic nerve head lie superficially in
retina and occupy a more central (deep) portion of
optic disc.

56. Thickness of nerve fibre layer at disc:
• Thickness of N.F.L around different quadrants of optic
disc margin progressively increases in following orders:
– Most lateral quadrant ( thinnest)
–Upper and lower temporal quadrant
–Most medial
– Upper and lower nasal quadrant ( thickest)

57. 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 (most lateral).
2. Arcuate nerve fibres which occupy the superior temporal
and inferior temporal quadrants of optic nerve head are
most sensitive to glaucomatous damage, accounting for an
early loss in corresponding regions of visual field.
3. Macular fibres occupying the lateral quadrant are most
resistant to glaucomatous damage and explain the
retention of the central vision till end.

58. Fundamentals and principles of
ophthalmology- AAO
Clinical anatomy of eye –snells
Wolf’s anatomy
Retina and vitreous- AAO section 12