3. Introduction : retina
Retina is the innermost layer of
the eye ball.
Thin delicate membrane
Thickness :
at the posterior pole – 0.56mm
at the equator – 0.18 to 0.2mm
at the ora serata 0.1mm
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4. Retina extends from the optic disc to the ora serrata and has
surface area of 266mm2
Ora serrata is the last region where the retina ends and ciliary
body starts; it consists of tooth like projections.
Retina is divided into two distinct regions:
posterior pole and peripheral retina separated by retinal equator.
On general examination divided into optic disk, macula lata, and
general fundus
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5.
6. Optic disc
The site where ganglion cell axons
accumulate and exit the eye
The optic disc lacks all retinal elements
except the nerve fiber layer and an internal
limiting membrane
Vertically oval Vertical diameter-1.8mm
Horizontal diameter- 1.5 mm
Anterior posterior width- 0.7-1mm in length
Pale center area-physiological cup
Horizontally oval
Free of nerve axon(cup)-0.3mm
Normal CDR= 0.4
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Photoreceptors are absent
here; hence known as blind spot.
7. Macula lutea
It is also called yellow spot
Fovea centralis is the central depressed part of
macula. It is about 1.5 mm in diameter.
An area about 0.8 mm in diameter(including
foveola and some surrounding area) does not
contain any retinal capillaries and is called foveal
avascular zone(FAZ)
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8. overview
Macula-
-Demarcated by superior and
inferior temporal arterial
arcuate
-Elliptical shape horizontally
-Average diameter of about
5.5 mm
-Area centralis corresponds to
approximately 15-18° of visual
field
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Fovea
-center of macula
-It has a diameter of 1.5-
1.85mm/1DD
-Represents 5° of the visual
field)
Foveola/fovea centralis
-Centre of fovea ( highest visual acuity)
-4 mm temporal to the centre of the
optic disc
and about 0.8 mm below the horizontal
meridian
-0.35mm in D/0.3-0.4DD
-corresponds to FAZ and 1° of
visual field
-Umbo (Center of foveola)
corresponds to light reflex
0.8mm
4 mm
Parafovea
-0.5mm around
the fovea
Perifovea
-1.5mm around
the parafovea
9. Peripheral retina (PR)
PR is divide into four parts
1.Near periphery
(1.5mm around the macula )
2.Mid-periphery
(3mm around the near periphery )
3.Far periphery
Extends 9-10 mm from optic disc on
the temporal side and
16 mm on the nasal side in the
horizontal meridian
4.Ora serrata.
Anatomical equator is located approximately
about 24mm from the center of optic disc
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5.5mm
Macula
1.5mm
3mm
9-10mm
16mm
11. 1. Retinal pigmented epithelium
It is the outermost layer of the retina.
It consist of a single layer of cells containing the pigment
melanin
It is firmly adherent to the underlying basal lamina (Bruch’s
membrane) of the choroid loosely attached to layers of rods and
cons
Space between sensory retina and RPE is subretinal space and
retinal detachment is common here.
Subretinal fluid(SRF)????
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12. 2. Layers of rods and cons
(neuroepithelium)
Transform light energy to visual impulse
Rods ( 40 -60µm ,cylindrical in shape) contain rhodopsin and serve
the peripheral vision and low illumination vision
Cons (40-80 µm, conical in shape) also contain photosensitive
substance responsible for phototopic vision ?? And color vision
We have 120 million rods and 6.5 million cons (fovea contains high
density of cons 199000/mm2 and it rapidly falls out side fovea)
Rods are absent at fovea and present in large number in ring shaped
zone 6 – 8 mm away from fovea
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13.
14. Blood supply of retina
Outer 4 layers of the retina- Choroidal vessels
Inner 6 layers- Central retinal artery which is a branch of Ophthalmic
artery.
Fovea is avascular but partially gets blood supply from choroidal
vessels
Macula- Central retinal artery and cilioretinal artery.
Central retinal artery emerges from the centre of the physiological
cup of optic disc and divides into 4 branches
These are end arteries i.e., they do not anastomose with each other.
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15.
16. Retinal capillaries
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Two capillary networks :
Superficial – lies at the level of
nerve fibre layer
Deep – lies between inner
nuclear and outer plexiform layer
17. 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.
18. Contents of the globe
Contents of the globe
include different
structures contained
in globe of the eye
these are lens,
aqueous humor, and
vitreous humor
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19. Lens
Lens is transparent, biconvex crystalline
structure between iris and vitreous
seated in patellar fossa, attached to
vitreous by Wiegert’s ligament, …. Berger’s
space , attache to ciliary prossess by
suspensory ligaments
Has layers of:-
--- nucleus
--- cortex
--- capsule
21. Equatorial
diameter
6.5mm at birth 9-10 mm at
extreme of age
Weight 135 at 0-9 years 255 mg at 40-50
years
Axial thickness 3.5 mm at birth 5 mm olders
Refractive index 1.39
Refractive power 16-17 D
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22. Lens transparency
Single thin layer of epithelum
Semipermiable character of lens
Sparcity and highly packed nature of lens cells
Pump mechanism of lens fibers
Avascularity of lens
Auto oxidation
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23. Accommodation
A process by which parallel rays of light coming from infnity are
brought in to focus in an emmetropic eye
Punctum proximum: nearest point at which small object can be
seen( 7cm at 10yrs, 25cm at 40 yrs, 33cm at 45yrs)
Punctum remotum: the farthest (infinity)
Distance between the two is range of accommodation
The difference between diopter to focus near point (p) and far point
( R ) is called amplitude of accommodation
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24. Aqueous humor
oIs a clear, colourless, watery
solution
oFlows from posterior to
anterior chamber
oIn healthy eye flow against
resistance generates 15 mm
hg
oVolume 0.31ml
oRefractive index 1.333
oPH 7.2
oHyper osmotic
oRate of formation 1.5 to
4.5 µl/min
25. Composition
Water constitutes 99.9% of Normal Aqueous
Proteins (5-16mg/100ml) concentration in Aqueous is less than 1% of its plasma
concentration
Glucose – 75% of the plasma concentration.
Electrolytes:
◦ Na+ similar in plasma and aqueous
◦ Bicarbonate ion: Concentration in PC & in AC
◦ Cl ion concentration than plasma and phosphate concentration than
plasma
Ascorbic acid concentration is very high in aqueous.
27. Functions of aqueous humor
Brings oxygen and nutrients to cells of lens, cornea, iris
Removes products of metabolism and toxic substances from those
structures
Provides optically clear medium for vision
Inflates globe and provides mechanism for maintaining IOP
High ascorbate levels protect against ultraviolet-induced oxidative
products, e.g., free radicals
Facilitates cellular and humoral responses of eye to inflammation and
infection
28. Aqueous humor dynamics
Secreted by ciliary epithelium lining the ciliary processes
Enters the posterior chamber.
It then flows around the lens and through the pupil into the AC.
There is convection flow of aqueous in the AC due to temperature gradiant.
It leaves the eye by two pathways at the anterior chamber angle:
◦ Through the TM, across the inner wall of Schlemm's canal into its lumen, and
thence into collector channels, aqueous veins, and the episcleral venous
circulation – the trabecular or conventional route
◦ Across the iris root, uveal meshwork, and the anterior face of the ciliary
muscle, through the connective tissue between the muscle bundles, the
suprachoroidal space, and out through the sclera – the uveoscleral or
unconventional route.
29. ANATOMY
Primary ocular structures involved are
1.Ciliary body
2.Posterior chamber
3.Anterior chamber
4.Angle of anterior chamber
5.Aqueous outflow system
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31. Aqueous humor formation
Aqueous humor is produced from pars plicata
along the crests of the ciliary processes.
Aqueous humor is derived from plasma within
the capillary network of the ciliary processes.
Three physiologic processes contribute to the
formation and chemical composition of the
aqueous humor:
◦ Diffusion
◦ Ultrafiltration
◦ Active secretion.
Lens
Pars
plicata
32. AQUEOUS OUTFLOW SYSTEM
Consists of two pathways
1.Trabecular or conventional
outflow
2.Uveoscleral or
unconventional outflow
37. BLOOD AQUEOUS BARRIER
• The tight junctions connecting
the apical portions of adjacent
non pigmented epithelial cells
forms the blood aqueous
barrier.
• Responsible for maintaining
the difference in chemical
composition b/w aq and
plasma
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39. Intra ocular pressure (IOP)
IOP : refers to the pressure exerted by the intraocular contents on
the coats of the eye ball .
Normal IOP is maintained by Aqhumor formation, outflow, episleral
venous pressure
Normal IOP ranges 10.5-20.5mmgh (mean being 15.5±2.57 mmhg)
Higher than body pressure ealswhere in the body by 5mmhg
Pulsatile
Dynamic function
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40. Factors affecting IOP
A. factors causing long term changes in IOP
heredity :
Age >40 yrs
Sex : in people >40 yrs F>M
Race:
Refractive error : myopics>emmetropics
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41. B. Factors causing short term
changes in IOP
Mean APB
SVP
Mechanical pressure on the
globe
Plasma osmolality
Blood PH
Durinal variation
Systemic hyperthermia
Seasonal variation
General anesthesia
Drugs
Vlockage of AQ humor
circulation
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43. Vitreous humor
Clear, avascular, gelatinous body, wt of 4gm bn retina and lens in the
posterior segment
comprises 2/3 of the volume of the eye
99% water ; 1% hyaluronic acid and collagen
firmly attached to the
OPTIC DISC
BACK OF LENS
FOVEAL REGION
ORA SERRATA
44.
45. extra ocular muscles
4 recti muscles
Superior rectus (SR)
Inferior rectus (IR)
Medial rectus (MR)
Lateral rectus (LR)
2 oblique muscles
Superior oblique (SO)
Inferior oblique (IO)
Purpose is to control the movement of the globe
51. Refraction of Light:
The cornea refracts 75% of the light transmitted
The rest is done by the lens
Image is projected on the retina, inverted, minimized and real.
52. Accommodation of the Lens:
The Lens is biconvex which intensifies the focusing power
The lens is flexible and can change curvature to accommodate
according to light and object distance
For far away objects: the zonule fibers provide tension to the
lens giving it an elongated shape
For close objects: ciliary muscles contract, relaxes the tension of
the lens leading to a rounder shape
55. Alignment of the Eyes:
Binocular vision: The two eyes field of vision overlap and
the image coincide creating a single impression
This is done by synced eye movements where both eyes
move simultaneously to maintain the overlap of vision.
57. Fusion:
Is the power exerted by
the eyes to keep the position
of the eyes aligned so that
the fovea can project
the same point in space.
58. Eye Movement:
Controlled by extraocular
muscles
To the left: levoversion
To the right: dextroversion
Upwards: sursumversion
Downwards: deorsumversion
59. Range of Focus:
For distances greater than 20 feet no accommodation is
required by the lens, but as this distance shortens the lens
has to accommodate and will thicken to clarify image.
60. Comparison between eye and camera:
Eye Camera
Diaphragm to
control the
amount of light
that gets through
to the lens
the pupil, at the center of the iris,
in the human eye.
the shutter in a camera
Method of sensing
the image
the image is focused on the retina film or sensor chip is used
to record the image
Method of
focusing
the focal length of the eye is
adjusted to create a sharp image.
This is done by changing the shape
of the lens; a muscle known as the
ciliary muscle does this job.
the lens has a fixed focal
length. If the object
distance is changed, the
image distance is adjusted
by moving the lens
62. THE VISUAL PATH WAY
CONNECT THE ON WITH THE OCCIPITAL
CORTEX
THE ON IS THE TRACT OF THE CENTRAL
NERVOUS SYSTEM
AFTER DAMAGE THE ON WILL NOT
REGENERATE
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64. As the retinal fibers leave the optic nerves ½ of them cross to the opposite side
The fibers that cross are derived from the retinal receptors nasal to the macula
Optic Chiasm – structure formed by the mutual crossing of nasal fibers by both optic
nerves
