Retina: By Ghulam Muhammad Optometry and orthoptics, UHS

1. RETINA

2. YOU DON’T NEED EYES TO SEE; YOU NEED VISION.
Presented by:
Ghulam Muhammad
2nd Year Optometry
Roll Number 04

3. HUMAN RETINA
Contents of Presentation
 Definition of Retina
 Where it is in the eyeball
 How it is developed
 Cells of retina
 Their arrangements
 Layers of retina
 Blood supply of retina
 Function of retina

4. DEFINITION OF RETINA
“It is a light sensitive, very thin delicate
membrane made of cells present inside the
eyeball”

5. WHERE IT IS IN THE EYEBALL
Retina is basically sandwich between choroid externally and vitreous humour
internally. There are three concentric layers of the eyeball. If we talk about
these from outside to inside these are;
1 Sclera
2 Uveal tract
1. Choroid
2. Ciliary body
3. Iris
3 Retina
So in this way Retina is the innermost layer of the eyeball

6. PARTS OF RETINA
Retinal
pigmented
epithelium
• Outer Retina
• Towards the choroid
Neuronal Layer
• Inner Retina
• Towards the vitreous body

7. PARTS OF RETINA
If you move on the retina anteriorly the light sensitive part of the
retina abruptly terminates at a point called “ Ora serrata”.
Where is Ora serrata situated ?
It is situated between the corneoscleral junction and equator of
the eye, or simply we can say that ora serrata is situated
between retina and Pars plana (posterior two-third of the ciliary
body). Anteriorly the retina terminates into a fingers like
projections. Actually these fingers like projections are called Ora
serrata. While the retinal pigmented epithelium along with some
components of neuronal layer continues anteriorly as an
epithelial layer on ciliary body and posterior side of the iris.

8. PARTS OF RETINA
Whenever we see retina through an ophthalmoscope; we can see only the
posterior retina around the optic disc and this part is called the “Ocular
Fundus”.

9. PARTS OF RETINA
When you look at the fundus you will find two landmarks.
1) Macula lutea (Also called as central retina).
2) Optic disc (Also called as blind spot).
Macula lutea
The macula lutea or simply macula is Yellowish area located inferolateral to
the optic disc and there is a slightly depression in the center of the macula
called “Fovea centralis”.
The fovea centralis is the region of sharpest visual acuity or the region of
maximum visual acuity due to large concentration of only cone cells. The
macula is avascular area and its diameter is from 5-6mm . It depends on
choriocapillaris for blood supply as it does not get blood supply from central
retinal artery.

10. PARTS OF RETINA
Optic disc
The optic disc is a point of retina from where all the optic nerve fibers are moving out of the retina
through the lamina ciribrosa and moving into the central nervous system as Optic nerve. The optic disc
located slightly nasally superiorly and medially.
There is also a depression in the optic disc called physiological cupping which is formed under certain
disease condition like glaucoma. The optic disc is deprived of photoreceptors cells therefore it is termed
as a blind spot .
MCQ’S: What is the best way to differentiate b/w optic disc and macula?
ANSWER: Optic disc is vascular while macula lutea is avascular.

11. Differentiate b/w Optic disc and Macula lutea?
Optic disc
i. Optic disc is pale color.
ii. It is located nasally.
iii. Here is depression called
physiological cup.
iv. Here is no light sensitive cells. So
a blind spot.
v. It is Vascular.
vi. It has sharp margins.
vii.It is smaller 1.5mm.
Macula lutea
i. Macula is yellowish color.
ii. It is located centrally and
inferolateral to optic disc.
iii. Here is depression called Fovea
centralis.
iv. Here light sensitive cells are
and it is the area of sharpest
v. It is avascular.
vi. It has diffused margins.
vii. It is larger 5 to 6mm.

12. DEVELOPMENT OF RETINA
Retina is derived from neural tube. There are three parts of neural tube
I. Prosencephalon or Forebrain
II. Mesencephalon or Midbrain
III. Rhombencephalon or Hindbrain
Now the prosencephalon are further divided into two parts;
 Telencephalon
 Diencephalon
From diencephalon special outpouching comes called optical vesicle. These
optical vesicle than developed into an optical cup having two layers of cells
outer and inner layer.
From the outer layer retinal pigmented epithelium is originated while from the
inner layer neuronal layer are originated.
Note : The Retina is the only part of the central nervous system which we
can see through an ophthalmoscope.

13. DEVELOPMENT OF RETINA
Prosencephalon
Diencephalon
Optical vesicle
Optical cup
Retina

14. DEVELOPMENT OF RETINA
The two layers which are coming out of optical cup are not held firmed with
each others due to this embryological difference of origination of the two
layers retina has two layers. Pigmented layer is tightly packed with choroid
and poorly with neuronal layer.
During retinal detachment (RD); it is the neuronal layer which moves inward
from pigmented epithelium while the pigmented Layer still attached with the
choroid. So practically retinal detachment is retinal dissection in which there a
space is created between neuronal and pigmented layer.

15. CELLS OF RETINA
The retina consists of two layers:
i. Pigmented layer
ii. Neuronal layer
The neuronal layer are pressed on the pigmented layer but it is made of many
cells. These are as follows;
 Epithelial cells
 Photoreceptors cells
 Neuronal cells
 Glial cells
How these cells are arranged in retina?

16. CELLS OF RETINA

17. CELLS OF RETINA
If we see cross section of the posterior eyeball we will find that there is;
a. Outermost sclera
b. Choroid
c. Retinal pigmented epithelium (inner to choroid)
Now anterior to RPE there are photoreceptors cells which are rods and
cones. Why they are called rods and cones because of their shape rods are
rod shaped while cones are cone shaped.
Individually there are four parts of each rod and cone;
I. Outer segment (which is photoreceptive)
II. Inner segment
III. Nucleus
IV. Synaptic terminal

18. CELLS OF RETINA
 Inside the retinal pigmented epithelial cells there are small granules called
melanosome. These absorbs the extra light.
 While in the cilia of the RPE photoreceptors are fixed.
 In the outer segment of Rods there are discs in which there ae visual
pigments called Rhodopsin.
 Next to the photoreceptors layer there is a layer of Bipolar cells.
 These are called bipolar because they have two poles; through one pole it
connects with the photoreceptors while at the other pole it attached with
the Glial cells.
 The part of bipolar cell which connect with the photoreceptor acts as a
dendrite while the part which connect with the glial cell acts as an Axon.

19. CELLS OF RETINA
 Note: Multiple rods can attach with one bipolar cell but only one cone
especially that of Fovea centralis can attach with one bipolar cell.
 Next to bipolar cells layer there is a layer of Ganglion cell.
 The glial cells have also two parts through one part they connect with the
bipolar cell (dendrite) while the other parts are a longed process called
Axons which carry the signals to optic disc than through the optic nerve to
the visual cortex.
 Now when the light falls on the eye it passes through cornea, anterior
chamber, posterior chamber, lens, vitreous humour, inner retina and fall on
photoreceptor cells which is plaster against the RPE.
 Now when the light falls on the rods and cones they produced Gradient
potential.

20. CELLS OF RETINA
 These gradient potential from rods and cones transfer into the bipolar cells
which causes chemical changes in them and they also produced Gradient
potential .
 From bipolar cells the gradient potential transfer into ganglion cells which
become modify the ganglion cells and they produce Action potential
because they have voltage gated Na+ channels.
MCQ’s: Main output neuron of the retina ?
Answer: Ganglion cells.
MCQ’s : Optic nerve is made of ?
ANSWER: Axon of the Ganglion cells.
 The current flow in these cells are radial means from outside to inside.
 RBG are glutaminergic means they use Glutamine as a neurotransmitter

21. CELLS OF RETINA
 There are also some cells which conduct the currents in lateral direction
they are called local conducting cells these are
1) Horizontal cells
2) Amacrine cells H.A.I cells
3) Interplexiform cells
 Actually these are the cells through which the rods and cones are
connected with each other and this is like medium in between them.
 The horizontal cells make connection with the photoreceptors at their
junction with the bipolar cells.
 Now this region where synapses formed between photoreceptors cell,
bipolar cells and horizontal cells is called Outer plexiform layer.

22. CELLS OF RETINA
 There are other cells which make connections at the junction of bipolar cells
and ganglion cells these are called Amacrine cells.
 This region where synapses formed between bipolar cells, ganglion cells and
amacrine cells are called inner plexiform layer.
 These two types of cells I .e Horizontal and Amacrine cells conduct the current
in retina in lateral direction.
 There are some other special cells which connect the outer and inner
plexiform layers these are called inter-plexiform cells.
 Inter-plexiform cells conduct the current in reverse direction
Plexiform: Network of synapses between different cells.
Outer plexiform layer:
i. Photoreceptors
ii. Bipolar cells
iii. Horizontal cells

23. CELLS OF RETINA
Inner plexiform layer:
i. Bipolar cells
ii. Ganglion cells
iii. Amacrine cells
Now as we know that these cells and components of the retina are very delicate
so they must keep at their proper positioned and there should be a proper
mechanism of insulation between different layers and cells . So the cells which
are responsible for placing all the retinal components at their propriate position
and make insulation between them are basically the Glial cells because their
basic function is protection. There are a type of Glial cells called Muller cells
whose nuclei are present in between the bipolar cells and two extensions radiate
from their nucleus one going to the outer retina while one go to the inner retina.
The other glial cells are astrocytes and microglial cells. The astrocytes support
the neuronal layer and the blood vessels here while the microglial cells are
macrophages present in the retina.

24. CELLS OF RETINA
The branch of muller cells which are going to outer retina divides into many
cilia which holds the inner segments of the photoreceptor cells.
These fine branches/cilia of the muller cells forming a fine delicate membrane
(actually this is not a true membrane but behaves as a membrane). This
membrane is called the outer limiting membrane.
The purpose of this membrane is to keep the photoreceptors at their proper
position and prevent the entry of inter-photoreceptor extracellular matrix to the
rest of the retina.
The second process of the muller cell which go into the inner retina up to
vitreous they make foot process. This foot process make another limiting
membrane between inner retina and vitreous gel. This membrane is called
inner limiting membrane. The nuclei of photoreceptor cells forming the
outer nuclear layer while the nuclei of bipolar cells, horizontal cells,
amacrine cells and muller cells forming the inner nuclear layer.

25. CELLS OF RETINA
R.B.G
• RPE.
• Bipolar cells.
• Glial cells.
H.A.I
• Horizontal
cells.
• Amacrine
cells.
• Inter-
plexiform
cells.
M.A.M
• Muller
cells.
• Astrocytes
• Microglial
cells.

26. LAYERS OF RETINA
1. RPE 2.Photoreceptors
3.Outer limiting
membrane

27. LAYERS OF RETINA
4. Outer
nuclear layer
5.Outer
plexiform
layer
6.Inner
nuclear layer

28. LAYERS OF RETINA
7. Inner
nuclear
layer
8.
Ganglion
cell layer
9. Nerve
fibers
layer
10. Inner
limiting
membrane

29. BLOOD SUPPLY OF RETINA
 The outer five layers of retina which are ;
i. RPE
ii. Photoreceptor layer
iii. Outer limiting layer
iv. Outer Nuclear layer
v. Outer plexiform layer
These are supplied by the choroicapillaries through diffusion.
These capillaries are derived from posterior ciliary artery . These have no
internal capillaries.
 While the inner five layers of the retina are supplied by the central retinal
artery CRA along with cilioretinal artery which supply to the macula.

30. FUNCTIONS OF RETINA
Converts light waves to
electrical signals.

31. FUNCTIONS OF RETINA
Functions of retinal pigmented epithelium:
i. Acts as a barrier between choriocapillaries and neuronal retina.
ii. It absorbs the extra light preventing scattering and internal reflection of
light so in this way it prevent the distortion of optical image. In albinos as
there is no melanin (melanosome) to absorbs the extra light, so there
occurs internal reflection therefore in albinos with the best optical
correction, still they can not have 20/20 vision.
iii. It maintain the integrity and functionality of the photosensitive parts of
rods and cons. As the photosensitive part of the rods and cons are taken
up by the RPE and these are regenerated to be use by the outer
segment of rods and cons. The RPE stores vit.A and also has the
capability to convert all-trans retinal to 11-cis retinal.

32. FUNCTIONS OF RETINA
iv. It also produces some growth factors. These growth factors are released
into choriocapillaries and rods and cons and maintain their structure and
function.
v. It also produces some immune suppressant. The purpose of these to
prevent any type of sever inflammation.
vi. Heat exchange.
vii. Formation of basal lamina of bruch membrane.
viii. Production of mucopolysaccharide matrix surrounding outer segments.
ix. Metabolism of vitamin A.

33. FUNCTIONS OF RETINA
 The retina is the light sensitive part of the eye. The light sensitive nerves
are the rods and cones.
 Whenever rays of light fall on these sensitive cells they cause chemical
changes in light sensitive pigments in these cells and they generate nerve
impulses which are conducted to the primary visual area (Area 17)of the
cerebral cortex in the occipital area via the optic nerve and finally to Area
18 which is the secondary visual area.
 In retina there are round about 100 million rods and 5 to 7 million cones.
 The rods are more sensitive to light than cones so they are used in dim
light while the cones are used in bright light.
 The normal rods and cone ratio in the retina is 16:1.
 Rods are numerous at the periphery of retina.

34. FUNCTIONS OF RETINA
 The visual pigment of rods rhodopsin become degraded when exposed to
bright light.
 Source of rhodopsin is vit. A.
 The monochromatic black and white vision is due to rods.
 The cones are sensitive to bright light and are used for sharp and color
vision.
 There are three basic types of cones in retina used for red, green and blue
colors.
 Binocular vision: the images from both the eyes are fused in the cerebrum
so that only one image is perceived.

35. THANKS