Anatomy and Clinical aspects of Retina

1. -Dr. Deepayan Sarkar

2. 1. Kanski’s Clinical Ophthalmology 8th Edition.
2. Yanoff Ophthalmology 5th Edition.
3. Wolff’s Anatomy of the Eye.
4. Khurrana Textbook of Ophthalmology.
5. Khurrana Anatomy and Physiology of the Eye. 3rd
Edition
6. Parsons Disease of the Eye.
7. Color Atlas and synopsis of Clinical
Ophthalmology- Retina. Wills Eye Hospital. 3rd
Edition.

3. •Innermost tunic of the eyeball.
•Extent- Extends from the optic disc to the ora serrata.
•Surface area- 266mm2
•Thickness- 1) Posterior Poles- 0.56mm
2) Equator- 0.18-0.22 mm
3) Ora serrata- 0.1mm
•Colour- Appears Purplish red due to the visual purple of the rods.

4. •Regions-
1) Optic Disc
2) Macula Lutea
3) Peripheral Retina

5. •It is a pale pink ,well defined circular area of about 1.5mm diameter.
•All layers of the retina terminate except the nerve fibre layers which run
through the lamina cribrosa into the optic nerve.
•Compared to the rest of the retina the optic disc appears pale due to the
lamina cribrosa, medullated nerve fibres behind the disc, and absence of
vascular choroid.
•Physiological cup in the optic disc is the depression seen in it, it is the
depression from where the optic nerve exits the eyeball.
•Central Retinal Artery the first branch of the Ophthalmic Artery gives rise to
four branches- Superior Temporal Retinal artery, Superior Nasal Retinal artery,
Inferior Temporal Retinal artery, Inferior Nasal Retinal artery.
•Central retinal vein also exits from here.

6. •It is a comparatively dark area 5.5mm in diameter situated at the posterior
pole of the eyeball temporal to the optic disc.
•It corresponds to 15 degree of the visual field and is responsible for
photopic vision and colour vision.
•It is rich in lutein and zeaxanthine which give yellow colour and have anti-
oxidant properties.
•Parts:
1) Fovea- It is about 1.50mm in diameter and 1.55mm in thickness. It
corresponds to 5 degree of visual field and is the most sensitive part of
the retina.
- Margo Fovea- Margin of the fovea can be seen biomicroscopically as a
ring like reflection of the internal limiting membrane.
- Foveola- 0.35mm in diameter forms the central floor of the fovea. It is
situated 2 disc diameters (3mm) from the temporal edge of the optic
disc and 1mm below the horizontal meridian. It is 0.15mm thick and is
characterized by underlying focal nuclear cake.
- Umbo- Tiny depression in the centre of the foveola which gives the
foveal reflex. Greatest concentration of cones is found at the umbo. It is
known as the central bouquet of cones.

7. -Clivus- It is the declinity extending from the margin of the fovea to the
margin of the foveola.
- Foveolar Avascular zone – Located inside the fovea but outside the foveola,
its exact diameter is determined by fluoroscein angiography. The other part
in the clivus is the peripheral vascular zone.
•Parafovea-Refers to the belt that measures 0.5mm in width and surrounds
the foveal margin.
•Perifovea- Refers to the belt that measures 1.5mm in width and surrounds
the parafoveal region.

8. Divide into 4 zones-
•Near Periphery- It is the circumscribed region of about 1.5mm width
around the macula lutea (a/k/a area centralis).
•Mid-Periphery- It occupies 3mm wide zone around the near periphery.Its
outer limit corresponds to the equator.
•Far Periphery-It extends from the equator to the ora serrata.
•Extreme Periphery- Refers to the area of ora serrata.

9. •Serrated peripheral margin where the retina ends
and the ciliary body starts. The dentate process
consisting of tooth like extensions of the retina on
the pars plana separated by oral bays, well marked
on the nasal half of the retina.
•At the ora serrata the sensory retina is firmly
attached both to the vitreous and RPE.
•Ora serrata is 2.1 mm wide temporally and 0.7-0.8
mm wide nasally.
•It’s distance from the limbus is 6mm nasally and
7mm temporally.
•It is the water shed zone between the anterior and
posterior system and so peripheral retinal
degenerations are more common here.

10. 1) Retinal Pigment Epithelium
2) Layers of rods and 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

11. •Outermost layer of the retina.
•The RPE shows fine mottling due to unequal
pigmentation of the cells, this gives the granular
appearance to the fundus.
•It is loosely attached to the layer of rods and
cones and firmly attached to the Bruch’s
membrane.
•The space between the RPE and the sensory
retina is known as the subretinal space.
•The adjacent RPE cells are connected by zona
occludentes and zona adherentes; and
constitutes the outer blood retinal barrier.
•RPE cells in cross-section can be differentiated
into-
Apical part & Basal part of RPEcells.

12. •Apical part- Formed by the microvilli which projects between
the rods and cone processes. At apical end of RPE cells overlie
about 45 photoreceptors.
Melanin pigments are concentrated here, it is stored in
melanosomes.
Lipofuschin accumulates gradually with age.
•Basal part- It has convulated infolds to increase surface area
for the absorption and secreation of materials, it lies in contact
with the Bruch’s membrane
Functions of RPE-
1) Photoreceptor renewal and recycling of Vit A.
2) Maintains integrity of subretinal space by forming outer blood
retinal barrier and pumping out ions and water out of the
subretinal space.
3) Transport of nutrients across the blood retinal barrier.
4) Phagocytic action by phagocytosis and digestion of
photoreceptors.
5) Provides mechanical support to the processes of the
photoreceptors and thus maintains retinal adhesions.
6) Electrical homeostasis.

13. • This layer contains the outer segment of
photoreceptors arranged in pallisade manner.
• It converts light energy into visual impulse.
•Rods contain Rhodopsin (visual purple) and
help in scotopic vision.
•Cones contain photosensitive substance for
photopic vision.
•Rods-120 million; Cones- 6.5 million.
• Structure of Photoreceptor-
-Cell body and nucleus- which lie in the outer
nuclear layer , cell process that extend into
outer plexiform layer.
- Inner and Outer segments – Forms the layer
of rods and cones.

14. • Outer segment- Contains rod
lamellae , it contains the visual
pigments.No. of rod lamellae (600-
1000/rod).
• Inner segment-
2 parts- a) Myoid region- Contains
the golgi bodies.
b) Ellipsoid region- Contains the
mitochondria and other cell
organelles.
• Outer Rod Fibre- Extends to the
Outer Nuclear layer
• Nucleus- Forms the Outer Nuclear
Layer
• Inner Rod Fibre- Extends to the
Outer Plexiform Layer.
• Rod spherule and Cone foot
process- Connect to the Bipolar
cell layer(1st order neuron)

15. •It appears as fenestrated membrane extending from the ora serrata
to the edge of the optic disc through which pass the rods and cones.
•It is formed by the junctions (zonulae adherentes) between the cell
membrane of the photoreceptors and Muller cells.

16. •Formed by the nuclei of the Rods and Cones.
•Cone nuclei are larger (6-7um) than the rod nuclei (5.5um)
and lie in a single layer next to the external limiting
membrane.
•Rod nuclei form the bulk of the outer nuclear layer except
the cone dominated foveal region.

17. •It consists of synapses between rod spherules and cone pedicles with
the dendrites of the bipolar cells and processes of the horizontal cells.
•It is the junction of end organ of vision and First order neuron.
•It is thickest at the macula and contains predominantly oblique fibres
that have deviated from the fovea and known as the Henle’s layer.

18. •It resembles the outer nuclear layer except it is thinner.
•It disappears at the fovea and in the rest of the retina consists
of-
1)Bipolar cells-
• 1st order neuron.
• The nuclear layer of the Bipolar cells lie here.
• The cells arborise with-
- Rods and cones- Outer Plexiform layer
- Dendrites of Ganglion cells- Inner Plexiform Layer.
• Types-
- Rod Bipolar cells- Have large soma which arborise only with
rod spherules.
- Midget Bipolar cells- Arborise with the cone pedicles.
Another variant is flat midget cells which donot invaginate the
cone pedicles but just touch them.
- Flat invaginating diffuse bipolar cells- The dendrites make
cone pedicle only and not with their triad.
- -Blue Bipolar cells- There are 2 varients – On centre or BBb
variety which arborise in stratum 5; Off centre or Bba variety
which arborise in stratum 1.
- Giant bipolar cells- Have large extent of dendritic spread.

19. 2)Horizontal cells- Flat cells having numerous horizontal associative
and neuronal interconnections between photoreceptors and bipolar
cells in the outer plexiform layer.
3)Amacrine cells- Situated within the innermost part of the layer. They
have piriform body and a single process which pass inwards in the
inner plexiform layer and forms connections with the axons of the
bipolar cells and the dendrites and soma of the ganglion cells.
4)Muller cells- The nucleus and cell body of the Muller cell bodies are
located in the inner nuclear layer. They extend from the External
limiting membrane to the Internal limiting membrane. The Muller cells
provide support to the retina and contribute to the metabolism of the
sensory retina.

20. Inner Plexiform Layer
• This layer consists of synapses between the axons of bipolar
cells (first order neuron) ,dendrites of ganglion cells(second
order neuron) and the processes of Amacrine cells.
• Fibres from the Muller cells courses vertically through this
layer and their side branches from the horizontal extending
reticulum.

21. • Forms the second order neuron of visual pathway.
•Throughout most of the retina ganglion cell is composed lof a
single row of cells,except in macular area it becomes multilayered
(6-8 layers); and on the temporal side of the disc it has two
layers.
•Types:
• W,X &Y ganglion cells.
•P(P1 and P2) and M ganglion cells.
•OFF centre and ON centre ganglion cells.
•Monosynaptic and polysynaptic ganglion cells.

22. • Also known as Stratum opticum.
• Consists of unmyelinated axons of the ganglion cells which
converge at the optic nerve head, pass through lamina cribrosa
and become ensheated by myelin posterior to lamina.
• In addition to axons of the ganglion cells,this layer also
contains-
- Centrifugal nerve fibres- Thicker than centripetal nerve fibres.
-Processes of Muller cells
-Neuroglial cells- Present in the nerve fibre layer are categorised
as macroglia and microglia.
-Retinal Vessels

23. • The nerve fibre layer courses parallel
to the surface of the retina in
contrast to the other fibres which
courses perpendicular to the
surface.
• Fibres from the nasal half of the
retina come directly to the optic disc
as superior and inferior radiating
fibres.
• Fibres from the macular region pass
straight in the temporal part of the
disc as papillomacular bundle.
• Fibres from the temporal retina arch
above and below the macular and
pappilomacular bundle as superior
and inferior arcuate fibres, with a
horizontal raphe in between.

24. •ILM mainly consists of a PAS positive true basement
membrane that forms the interface between retina and
vitreous.
•The fibrils of the vitreous merge with the internal lamellae
of this membrane .
•Externally the basal foot processes of the Muller’s cells abut
with the membrane and probably play a role in its formation
•It consists of-
•Collagen fibrils
•Proteoglycans
•Basement membrane
•Plasma Membrane of the Muller cells and other glial cells
of the retina.

25. • Outer 4 layers (RPE, Layers of rods
and cones, ELM,ONL) are supplied by
the Chorio-capillaries.
• The inner 6 layers(OPL, INL, IPL,
Ganglion cells, Nerve fibre layer and
Internal limiting membrane) of the
retina get their nutrition from the
Central retinal artery.
• The Outer Plexiform Layer gets its
blood supply from the central retinal
artery and partly by diffusion from
Chorio capillaries.
• Fovea is an avascular structure mainly
supplied by the Chorio-capillaries.
• Macular region gets its blood supply
by the twigs from the superior and
inferior branches of central retinal
artery and sometimes by cilioretinal
artery

26. Blood Supply of Optic nerve
• Surface nerve fibre layer- Mainly
supplied by the capillaries
derieved from the retinal
arterioles. Occasionally a ciliary
derieved vessel the cilio retinal
artery.
• Prelaminar region- Supplied by
the vessels of the ciliary region,
vessels of choroid and short
posterior ciliary artery.
• Lamina Cribrosa- Supplied by the
ciliary vessels which are derieved
from the short posterior ciliary
artery and the arterial circle of
Zinn-Haller.
• Retrolaminar- Supplied by both
ciliary and retinal circulation.

27. APPLIED ANATOMY

28. • It is bilateral optic disc swelling that is caused
by increased intracranial pressure due to any
cause.
• Thickness of the nerve fibre layer at the disc-
-Most lateral quadrant (Thinnest) < Temporal
fibres < Most Medial Quadrant < Nasal
Quadrant (thickest)
• Papilloedema appears first of all in the
thickest fibres, hence the nasal quadrant are
first to be involved.

29. Glaucomatous changes
• The Arcuate nerve fibres which
occupy the superior and inferior
temporal quadrants of the optic
nerve head, are the most sensitive
to glaucomatous damage.
• The macular fibres are most
resistant to glaucomatous
damage and it explains the
retention of the central vision till
the end.

30. Retinal Detachment
• Detachment of the RPE from the
neurosensory retina, is known as
Retinal detachment. It is because
the RPE is strongly adhered to the
Bruch’s membrane and the
Neurosensory retina is held
together by the Muller cells
(supporting cells) and the
interweaving of the photoreceptor
layer.
• Break at any other point in the
retinal layers is known as
Retinoschisis.

31. •Pigment Epithelial Detachment is structural
spiliting of the Bruch’s membrane, leading to
detachment of the RPE from the Bruch’s
membrane.
• Seen in Vogt-Koyanagi-Harada (VKH)
Syndrome, Idiopathic Central Serous
Chorioretinopathy (CSC) small multifocal
idiopathic PEDs, Polypoidal Choroidal
Vasculopathy (PCV), and Exudative/Non-
Exudative Age-Related Macular
Degeneration (AMD).
•Age-related deposition of lipids, such as
cholesterol esters, triglycerides, and fatty
acids in Bruch's membrane may change its
permeability altering retinochoroidal flow
leading to fluid accumulation in the sub-
RPE space, unable to pass through Bruch
membrane, resulting in RPE elevation.

32. •Idiopathic disorder charecterised by
localised serous detachment of the
sensory retina at the macula
secondary to leakage of the
Choriocappilaries.
•It is due to the breakdown of the
Outer Blood Retinal Barrier. – The
Outer Blood Retinal barrier is
composed of tight junctions (Zonula
Adherantes and Zonula Occludentes)
of the RPE cells and the cappilaries.
•It is also due to the breakdown of
the RPE pumps, which pump out
fluid from the sub retinal space.

33. •It results from the accumulation of
fluid in the outer plexiform and
inner nuclear layers of the retina
forming cyst like cavities.
Causes- Ocular surgeries and laser,
Retinal vascular disease,
Inflammation, Prostaglandin
induced, Retinitis Pigmentosa,
Presence of ERM, Choroidal
neovascularisation, Fundus
tumour, Chronic renal failure.

34. •Feather- or flame-shaped
hemorrhages has indistinct borders
and blood accumulates at the level of
superficial nerve fiber layer.
•Hemorrhage is from the superficial
capillary plexus.
•Seen in Hypertensive retinopathy,
Diabetic Retinopathy,Sarcoidosis.

35. •Dot and blot hemorrhages occur as
microaneurysms rupture in the
deeper layers of the retina, such as
the inner nuclear and outer plexiform
layers.
•Commonly seen in association with
diabetic or hypertensive retinopathy
and retinal vein occlusion.
•Peripapillary hemorrhage in patients
with normal tension glaucoma is
also called splinter hemorrhage

36. Drusens
• Drusens are subretinal pigment
epithelial deposits between the RPE
and the Bruch’s Membrane.
• They represent degenerative products
of RPE, they are composed of lipids
and glycoproteins may harbour
immunocomponents and may be
mineralised.
• It is found in the RPE layer in OCT.

37. •Cotton wool spots are abnormal
finding on funduscopic exam of
the retina .They appear as fluffy
white patches on the retina.
•They are caused by damage to
superficial nerve fibers and are a result
of accumulations of axoplasmic material
within the nerve fiber layer.
Causes: Hypertension, diabetes, ocular
ischemic syndrome, retinal vein
occlusion, anemia, radiation, acute
blood loss.Systemic lupus
erythematosus, dermatomyositis, , Giant
cell arteritis,HIV retinopathy,.

38. •It is the dystrophy of the retinal
pigment epithelium generally of the
rod photoreceptors and in advanced
stages involve the cones.
•It is genetic is nature with sporadic
transmission being the most common
varient.
•It is charecterised by bony spicules
retinal pigmentation, optic disc pallor
and arteriolar attenuation.

39. •These are mostly cone-rod dystrophies
with cones being affected earlier and more
severely.
•Sporadic transmission.
•Presentation in early adulthood.
•Macula may be normal or show non-
specific central pigmentary changes.
•Bull’s eye maculopathy changes may be
found.
•Patient presents with gradual bilateral
impairement of central and colour vision,
some may also present with photophobia.

40. •It is the clinical finding seen on fundus
examination in which the posterior pole
loses transperency at the retina.
•It is because of oedema of the Outer
Plexiform layer/ Henle’s layer. This layer is
absent at the fovea.
•The fovea shows the red hue and appears
as cherry red spot on a pale background.
•Seen in – Niemann-Pick disease,
Retinotoxicity, Tay-Sach’s, Sandhoff disease,
Commotio retinae.

41. • Sudden profound loss of vision due to
occulusion of the central retinal artery.
• Generally Painless except in case of Giant
cell Arteritis.
• VA is reduced.
• RAPD is profound.
• Fundus finding- Orange reflex from the
intact choroid, Cherry-red spot.
• OCT- Highly reflective embolic plaque
within the superficial optic nerve head.
• FFA- Variable delay in arteriolar finding.

42. • Sudden painless loss of mono-ocular vision
• VA- Impaired to variable degree depending
on the severity
• RAPD- Absent/mild.
• Fundus: Tortuosity and dilatation of all
branches of the central retinal vein, with dot-
blot haemorrhage, flame shaped
haemorrhage, cotton wool spots, optic disc
and macular oedema.
• OCT- Macular oedema is noted
• FFA- Show characteristic fern like perivenular
auto-fluroscence due to masking of signals
due to oedema.