INTRODUCTION
• Retina isthe innermost layer of the eyeball
• It is the most highly developed tissue; thin ,
delicate , transparent , multi-layered sheet
of neural tissue that lines the inner aspect
of the posterior two-thirds of the wall of
the globe
• Responsible for photochemical transduction
and generation of visual electrical impulses
• Consists of two primary layers : an outer
RPE(retinal pigment epithelium) and inner
neurosensory retina
5.
DEVELOPMENT OF RETINA
-isdeveloped from NEUROECTODERM
FROM NEURAL PLATEOPTIC VESICLE
(3RD
WEEK OF GESTATION)
6.
DEVELOPMENT OF RETINA
•During the 4th
week, the optic vesicle gets
converted into double layered structure
called the OPTIC CUP,owing to differential
growth of the walls of the vesicle
• It is developed from 2 parts of optic cup
1.Optic cup-outer layerretinal pigment
epithelium
-starts around 6th
week of gestation
2.Optic cupinner layerneurosensory retina
7.
RETINAL DETACHMENT:
-Is aseparation of retinal pigment epithelium from neurosensory
layer
-can be of 3 types-
1.Rhegmatogenous
2.Tractional
3.Exudative
8.
GROSS ANATOMY
• Extent-from ora serrata to optic disc
• Colour- appears purplish-red due to visual purple of
the rods
• Surface area- 266mm2
• Regions- grossly divided into:
1. Optic Disc
2. Central retina/area centralis/Macula lutea
3. Peripheral retina with ora serrata
• Thickness- at optic disc(thickest):approx.0.56mm
at the equator:approx. 0.18mm to 0.20mm
at the ora serrata:approx. 0.1mm
11.
• OPTIC DISCis a circular to slightly vertically oval
structure where all the retinal layers terminate except
the Nerve Fibre Layer, which pass through the lamina
cribrosa
• Appears pale-pink(in comparison with the rest of retina)
due to Lamina Cribrosa, medullated nerve fibres behind it
and absence of vascular choroid
• PHYSIOLOGICAL CUP is a depression in the optic disc
centrally, through which the central retinal vessels
emerge
• Diameter:1.5mm
THE OPTIC DISC
12.
OPTIC DISC
• Normalcup-disc ratio:0.3 – o.4
• Neuroretinal rim: around the disc
-pink and sharp peripheral margins
-contains nerve axons
-broad:inferior rim>superior>nasal>temporal
13.
MACULA
• Also knownas AREA CENTRALIS/CENTRAL
RETINA/POSTERIOR POLE/MACULA LUTEA
• Situation- at the posterior pole of the eyeball, temporal to
the optic disc between the temporal vascular arcade
• Function: photopic vision and colour vision
• Diameter:5.5mm(3.5DD)
• It is divided into:
FOVEA/FOVEA CENTRALIS
FOVEOLA
PARA-FOVEAL(0.5mm ring)
PERI-FOVEAL(1.5mm ring)
14.
MACULA LUTEA
• FOVEA-isthe central depressed part of macula
-the most sensitive part of retina
-diameter:1.5mm(1 DD)
-thickness:1.55mm
• FOVEOLA-forms the central floor of the fovea
-situation:3mm(2 DD) away from the temporal edge of the optic
disc
-diameter:0.35mm
-thickness:0.15mm
• PARAFOVEA-refers to a belt of 0.5mm in width surrounding foveal
margin
• PERIFOVEA-refers to a belt of 1.5mm in width surrounding parafoveal
area
15.
MACULA
• Umbo isa tiny depression at the very centre of foveola which
corresponds to the ophthalmoscopically seen foveolar reflex.
- greatest concentration of cones is found in the umbo referres to
as the CENTRAL BOUQUET OF CONES
• FOVEAL AVASCULAR ZONE is located inside the fovea but
outside the foveola
16.
PERIPHERAL RETINA
• NEARPERIPHERY-refers to a circumscribed region of
about 1.5mm width around macula lutea
• MID PERIPHERY-a 3mm wide zone around the near periphery
• FAR PERIPHERY-extends from equator to the ora serrata(9mm
on temporal side and 16mm on nasal side)
• EXTREME PERIPHERY-refers to the area of ora serrata and pars
plana(remaining 2.1mm on temporal and0.7mm on nasal side)
• ORA SERRATA-the most anterior region of retina
-is the serrated peripheral margin where the retina ends and
ciliary body starts
17.
• ORA SERRATA-
-consistsof dentate fringe which denotes the termination of the
retina
-DIMENSIONS:2.1mm wide temporally and 0.7-0-0.8mm wide nasally
-LOCATION:6 mm nasally and 7mm temporally from the limbus, 6-
8mm from equator and 25mm from the optic nerve on the nasal side
-it is a water shade zone between anterior and posterior vascular
system
-peripheral retinal degenerations are more common
MICROSCOPIC STRUCTURE OFRETINA
• 1. RETINAL PIGMENT EPITHELIUM
-it is the outermost layer of retina
-it is a single layer of approx. five million hexagonal shaped cells
-shows fine mottling due to unequal pigmentation of cells-gives
granular appearance of the fundus
-it is firmly attached to underlying Bruch’s membrane(basal
lamina of choroid) and loosely attached to layer of rods and
cones of the sensory retina
-Subretinal space:a potential space between RPE and the sensory
retina
-adjacent RPE cells are connected with each other by tight
junctions(zona occludens) and form OUTER BLOOD RETINAL
BARRIER
RPE CELL
• ONELECTRON MICROSCOPE,
• -The RPE cells at the fovea are taller,thinner and contains more and large
granules than elsewhere in the fundus thereby giving a dark color to this
area
• -The optical part of RPE formed by the microvilli which project b/w the
rods and cones processes
• -RPE cells in cross section, can be differentiated into
1.Apical configuration
-microvilli present which project between the rods and cones processes
-melanin granules are present
2.Basal configuration
-convulated infolds to increase surface area for the absorption and
secretion of material
-lies in contact with the Bruch’s membrane of choroid
25.
FUNCTIONS OF RPE
•Imp role in photo receptor renewal and recycling of vit A
• Maintain integrity of subretinal space by forming the outer blood
retinal barrier
• Transport of nutrients and metabolites through blood retinal
barrier
• Phagocytic action by phagocytosis and digestion of photoreceptors
• Provides mechanical support
• Manufectures pigment
• Regenerative and reparative function
THE LAYER OFRODS AND CONES
• RODS and CONES(PHOTORECEPTORS) are the end organs of vision which transform
light energy to into visual(nerve) impulse
• Rods contain a photosensitive substance visual purple(rhodopsin) and responsible
for peripheral vision and vision of low illumination(scotopic vision)
• Cons contain iodopsin pigment(a photosensitive substance) and are responsible for
highly discriminatory central vision(photopic vision) and colour vision
• Number of photoreceptors:there are about 120 million rods and 6.5 million cones
• distribution of rods:-rods are absent at the fovea(o.35mm)
-they are present in a large number(1,60,000/mm2) in a ring shaped zone 5-6 mm
from the fovea.
-these are maximum below the optic disc(1,70,000/mm2) and number reduces
towards the periphery
28.
LAYER PF RODSAND CONES
• Distribution of cones:-the highest density of cones is at fovea with an average of
1,99,000/mm2(number is highly variable)
-the number of cones falls of rapidly outside the fovea;being only 6000cones/mm2
3mm away from fovea and about 4000cones/mm2 10mm away
STRUCTURE OF RODS AND CONES-
• Extending from their cell bodies, photoreceptors have two morphologically distinct
regions: the inner and outer segments
• The outer segment lies embedded in the interphotoreceptor matrix, in close
approximation with the RPE. Its major function is conversion of light energy to
electric impulses, which takes place with the help of visual pigments
30.
STRUCTURE OF PHOTORECEPTORS(IN
RELATIONTO VARIOUS LAYERS)
PART OF PHOTORECEPTOR LAYER
CELL BODY AND NUCLEUS OUTER NUCLEAR LAYER
CELL PROCESS OUTER PLEXIFORM LAYER
INNER AND OUTER SEGMENTS LAYER OF RODS AND CONES
31.
EXTERNAL LIMITING MEMBRANE
•A fenestrated membrane extending form the ora
serrata to optic disc through which processes of the
rods and cones pass
• Ultramicroscopically, the ELM is shown to be composed
of terminal bars(zonulae adherents) between muller
cells and cell membrane of photoreceptors
• Main functions of the ELM include providing a
SELECTIVE BARRIER FOR NUTRIENTS which pass
between adjacent muller cells and STABILISING THE
POSITIONS of the transducing portion of photoreceptors
32.
OUTER NUCLEAR LAYER
•Primarily formed by the nuclei of rods and cones
• Cone nuclei are somewhat larger than the rod nuclei and lie in a
single layer next to the external limiting membrane
• Rod nuclei form the bulk of this multi-layered outer nuclear layer
except in cone dominate foveal region
• Number of rows of nuclei and thickness of this layer varies from
region to region:
Nasal to the disc 8-9 layers of nuclei 45microm thickness
Temporal to the disc 4 rows of nuclei 22 microm
Foveal region 10 raws of nucei 50 micrim
Rest of the retina except ora
serrata
1 row of cone nuclei and 4
rows of rod nuclei
27mm
33.
OUTER PLEXIFORM LAYER
•This layer contains synapses between rods spherules and
cone pedicles with the dendrites of the bipolar cells and
processes of the horizontal cells
• This layer marks the junction of the end organs of vision
and first order neurons of the retina
• It is the thickest at the macula(51 micrometer) and consists
of predominantly of oblique fibres that have deviated from
the fovea and is also known as HENLE’S LAYER
• Dot and blot haemorrhage and hard exudates are seen in
this layer
34.
INNER NUCLEAR LAYER
•Resembles outer nuclear layer except that it is very thin
• Consists of:
1.Horizontal cells(the outermost layer)
2.Bipolar cells(8-12 rows of closely packed nuclei)(the outer
intermediate layer)
3.The soma of the muller cells(the inner intermediate layers)
4.Amacrine cells and interplexiform cell nuclei(the innermost
layer)
• Disappears at fovea
36.
HORIZONTAL CELLS
• Theseare flat cells having numerous horizontal associative
and neuronal interconnections between photoreceptors and
bipolar cells in outer plexiform layer
• These are of 2 types:(depending upon the size of the cells and
the type of synapses made by the dendrites and axons)
1. Type A- have 7 groups of dendrites which have contact with
triad of 7 cone pedicles and their single axon has contact with
distant cone triad
2. Type B- dendrites have contact with rod receptors only
and their axons with the distant rod cells
37.
BIPOLAR CELLS
• Bipolarcells are the first order neurons in the visual pathway
• The body of the bipolar cells consists entirely of the nucleus which lies in
the inner nuclear layer while their dendrites arborize with the rod
spherules and cone pedicles in the outer plexiform layer and their axons
arborize with the dendrites of ganglionic cells in the inner molecular layer
• On the basis of morphology and synaptic relationship, nine types of bipolar
cells are seen under light microscopy:
1. Rod bipolar cells
2. Invaginating midget bipolar cells
3. Flat midget bipolar cells
4. Invaginating diffuse bipolar cells
5. Flat diffuse bipolar cells
6. On-centre blue cone bipolar cells
MULLER’S CELLS
• Thenucleus and cell bodies of the muller’s cells are located within
the inner nuclear layer
• Fibres from their outer ends extend up to the externa limiting
membrane and those from their inner ends reach upto the internal
limiting membrane
• Muller’s cells provide structural support and contribute to the
metabolism of the sensory retina
40.
AMACRINE CELLS
• Thesecells are situated in the innermost part of the
inner nuclear layer
• These have a piriform shaped body and a single process
which passes inwards in the inner plexiform layer and
forms connections with the axons of the bipolar cells
and the dendrites and the soma of ganglion cells
42.
THE INNER PLEXIFORMLAYER
• Consists of synapses between the axons of bipolar cells(first
order neuron), dendrites of ganglion cells(second order neuron)
and the processes of integrative amacrine cells
• Fibres from the muller’s cells courses vertically through this
layer and their side branches form the horizontal extending
reticulum
• This layer is absent in foveola
• It is thicker and has more synapses per unit than the outer
plexiform layer
44.
GANGLION CELL LAYER
•The cell bodies and the nuclei of the ganglion cells(Second order
neuron of visual pathway)lie in this layer
• Composed of a single row of cells, except in the macular region
where it becomes multi-layered(6-8 layers of the cells) and on the
temporal side of the disc where it has 2 layers
• It is absent in the region of foveola
• Around 1.2 million ganglion cells are present in the retina, each
producing a single axon which converge and exit the eye as optic
nerve
45.
NERVE FIBRE LAYER
•Consists of the unmyelinated axons of ganglion cells(centripetal or
afferent fibres) which converge at optic nerve head, pass through
lamina cribrosa and become enshithed by myelin posterior to lamina
• It also contains centrifugal nerve fibres, processes of Muller’s cells,
neuroglial cells(macro and micro) and retinal vessels(a rich bed of
superficial capillary network is present)
• The nerve fibres vary in their thickness from 0.5 to 2 micrometer
• Flame shaped haemorrhages and soft exudates seen in this layer
46.
NERVE FIBRE LAYER
•Arrangement of nerve fibres in the Retina:
-fibres from nasal half of the retina come directly to
the optic disc as superior and inferior radiating fibres
-fibres from macular region pass straight in the
temporal part of the disc as papillomacular
bundle(PMB)
Fibres from temporal retina arch above and below the
macular and papillomacular bundle as superior and
inferior arcuate fibres with a horizontal raphae in
between
• Nerve fibre layer is the thickest at the nasal edge of
the disc and thinnest around the optic disc
47.
NERVE FIBRE LAYER
•Arrangement of nerve fibres of the optic disc /optic
nerve head:
-optic nerve comprises 1.2 million nerve fibres
-fibres from peripheral part of the retina lie deep in the
retina but occupy most peripheral(superficial) part of the
optic disc
-while the fibres originating closer to the optic nerve head
lie superficially in the retina and occupy a more
central(deep) portion of the disc
-papillomacular bundle is the last portion to get affected in
papilloedema
48.
Clinical significance ofdistribution of nerve
fibres at OD margin
• Papilloedema occurs first in the thickest quadrant(upper nasal and
lower nasal) and last of all in the thinnest quadrant(most lateral)
• Arcuate nerve fibres which occupy the superior temporal and
inferior temporal quadrants of optic nerve head are most sensitive
to glaucomatous damage
• Macular fibres occupying the lateral quadrant are most resistant to
glaucomatous damage
49.
INTERNAL LIMITING MEMBRANE
•Innermost layer of retina
• Mainly consists of a PAS positive true basement membrane that forms
interface between retina and vitreous
• Consists of 4 elements:
1.Collagen fibrils
2.Proteoglycan (mostly hyaluronic acid) of the vitreous
3.Basement membrane
4.The plasma membrane of the muller cells
It is the thickest at the fovea and is absent at the edge of optic disc
50.
BLOOD SUPPLY
• Outer4 layers of retina get their blood supply from
choriocapillaris
• Inner 6 layers get their blood supply from the central retinal
artery
• Outer plexiform gets it blood supply partly from central retinal
artery and partly from choriocapillaris by diffusion
• Fovea is an avascular area mainly supplied by the choriocapillaris
• Macular area gets its supply from the superior and inferior
temporal branches of central retinal artery
51.
BLOOD SUPPLY
• RETINALVESSELS ARE END-ARTERIES but anastomosis does exist
between retinal vessels and the ciliary system of vessels with the
vessels which enter the optic nerve head from the arterial circle
of zinn or haller
• This arterial circle is formed by 2 and 4 or more short posterior
ciliary arteries and lies in the sclera around the optic nerve
52.
CENTRAL RETINAL ARTERY
•Is the first branch of the ophthalmic artery which is a branch of
the internal carotid artery,arises near the optic foramen
• In the retina, central retinal artery divides into a superior and an
inferior branch ,each of which subdivides into a nasal and a
temporal branch
53.
Arrangement of retinalcapillaries
• EXTRAMACULAR FUNDUS
-capillary network in retina is arranged into 2 layers:superficial and
deep
-Superficial lies at the level of NERVE FIBRE LEVEL and deep lies
between inner nuclear and outer plexiform layer
-the deep capillary network is more dense and complex than the
superficial
• PARAFOVEAL ZONE:
The capillary network is 3 layered. The foveal avascular zone is
capillary free
• PERIPAPILLARY REGION:
Capillary network becomes 4 layered
Most read
Most read
Most read
![ANATOMY AND PHYSIOLOGY OF RETINA ( Part 2)[1].pptx](/proxy?url=https%3A%2F%2Fcdn.slidesharecdn.com%2Fss_thumbnails%2Fanatomyandphysiologyofretinapart21-240517062838-be6d6faf-thumbnail.jpg%3Fwidth%3D640%26height%3D640%26fit%3Dbounds)
