monikanafsu-150904083756-lva1-app6892.pdf

Anatomy of retina

1. RETINA
monikapallan&
afasanapathan
ANATOMY & PHYSIOLOGY

2. Retina
•Retina is the innermost tunic of the eyeball
•Thin,delicate,transparentmembrane
•Highly developed tissue of the eye
•Appears purplish red

3. Grosssanatomy
•Three distinct regions of retina:
•1.optic disc
•2.macula lutea
•3.peripheral retina
•retina extends from optic disc to oraserrata
•Surface area:266sq/mm

4. Optic disc
•Pale pink in colour; well defined circular area
•Diameter: 1.5mm
•All the retina layers terminate here,exceptthe
nerve fibrewhich pass through the lamina
cribrosa

5. Macula lutea
•The macula luteais comparatively dark area
5.5 mm in diameter , situated at the posterior
pole of the eyeball , temporal to optic disc
•also called as yellow spot or area centralis
•Primary function :-photopticvision
•Fovea centralisis central depression in
macula;measurin1.85 mmindiameter & 0.25
thickness
•It is most sensitive part of retina

6. Foveola
•Diameter:-0.35
•Central floor of fovea
•Umbo is the tiny depression in centreof
foveola
macula
Fovea centralis
foveola
umbo

7. Peripheral retina
•The peripheral retina can be divided into four
regions
1.Near periphery
2.mid periphery
3.Far periphery
4.Oraserrata

8. Microscopic structure of the retina
1.Retinal pigment epithelium
2.Layer of rods and cones
3.External limiting membrane
4.Outer nuclear layer
5.Outer molecular (plexiform) layer
6.Inner nuclear layer
7.Inner molecular (plexiform) layer
8.Ganglion cell layer
9.Nerve fibrelayer
10.Internal limiting membrane

9. Retinal pigment epithelium (RPE)
•It is the outermost layer of retina
•Made up of single layer of hexagonal cells
•The cells contain pigments
•It is firmly adherent to the underlying brush
layer & loosely attached layer of rod and cone
cells
•Sub-retinal space :-potential space betnRPE
& retina

10. Conts……
•Retinal detachment :-separation of RPE from
retina
Sub-retinal fluid :-fluid betnsensory retina &
RPE
. RPE cells are connected to each other by
zonuleoccludents& zonuleadherence

11. Functions of RPE
•Renewal of photoreceptor & recycling of VitA
•Provides mechanical support to process of
photoreceptors
•Manufacturing of pigments absorbing light
•RPE cells are phagocytic

12. Layer of Rods & Cone cells
•Rods & cones transform light energy into nerve
impulses
•Rods contain photosensitive substance
rhodopsin whereas cones contain photosensitive
substance idopsin
•Cone cells -photopticvision
•rod cells -scotopticvision
Cones :-6.5 million
Rods :-120 million

14. Conts……
•At fovea:-max cones(199000cones/mm.sq) &
rods are absent
•Density:-100000-324000 cones/mm.sq
• 160000 rods/mm.sq

15. Structure of rod cell
•Length :-40-60 um
•Outer segment is cylindrical composed of
numerous protein lamellar disc
•Dics:-600-1000/rod
•Thickness of disc :-22.5 -24.5 nm
•Disc contains 90% of visual purple
•Outer segment is attached to inner
segment via cilium
•Inner segment :-consist of ellipsoid &
myoidregion
•

16. Conts…..
•Outer rod fibrearises from inner end of rod &
passes through external limiting memebrane
further swells into densely stained nucleus
•The nucleus terminates further into inner rod
fibre
•The inner rod fibreends as a bulb called rod
spherule

17. Cone cells
•Length :-40-80um
•At periphery :-40um ( shortest)
•At fovea :-80um (longest)
•Outer segment is conical :shorter than rod
•Contains idopsinpigment packed in lamellar disc
•Disc :-1000-1200 disc/cone
•Inner segment & cilium are similar to rods
•Inner segment is directly continouswith nucleus
•A stout cone inner fibreruns from the nucleus & has
lateral processes at the end called cone foot / cone
pedicel

18. External limiting membrane
•Fenestrated membrane extending from the
oraserratauptothe edge of optic disc
•Processes of rods & cones pass through it
•This layer is formed by the junction betnthe
cell membrane of photoreceptors & mullers
cell

19. Outer nuclear layer
•Made up of the nuclei of rods & cones
•Cone nuclei:-6-7 um
•Rod nuclei :-5.5um
•These nuclei lie in a single layer next to
external limiting membrane
•Rod nuclei form the bulk of this layer except at
cone dominated fovealregion

20. Variation in Thickness
•Nasal to disc:-45um ( 8-9 layers )
•Temporal to disc :-22um (4 rows)
•Fovealregion :-50um (10 rows)
•Rest of retina except oraserrata–27 um (1
row of cones & 4 rows of rods)

21. Outer plexiformlayer
This layer is made of synapses betnthe rod
spherules & cone pedicles with the dendrites of
bipolar cells

22. Inner nuclear layer
•It is very thin & is similar to outer nuclear
layer
•It consists :-
Bipolar cells
Horizontal cells
Amacrinecells
Mullerscells
Central retinal vessels
Other glial cells
This layer disappersat fovea

23. Inner plexiformlayer
•Consists of synapse betnbipolar cell &
dendrites of ganglion cell
•Absent at fovea

24. Ganglion cell layer
•Consist of cell body & nuclei of ganglion cell (
2
nd
order neurons)
•Absent at fovea
•Various types of ganglion cell:-
1)W,X,Y ganglion cell
2)P(P1 &P2) & M GANGLION CELL
3)Off centre& on centrecell
4)Monosynaptic & polysynaptic cell

26. Nerve fibrelayer
•Consists of unmyelinatedaxons of ganglion
cells which converge at optic nerve head
•Thickness:-0.5-2 um
•Thickness decreases from optic disc to lateral
side
•Fibresshow definite pattern of arrangement

27. Internal limiting membrane
•Consists of following elements:-
•1) collagen fibrils
•2) proteoglycans of vitreous
•3) basement membrane
•4) plasma membrane of mullercells
•5) other glial cells

28. Blood supply of retina
•Outer 4 layers :-choriocapillaries
•Inner 6 layer:-central retinal artery
•Fovea :-choriocapillaries
•Macular region:-superior & inferior temporal
branches of central retinal artery

29. PYSIOLOGY OF
RETINA

30. PHYSIOLOGY OF VISION
•It is a complex phenomenon
•Main mechanism concerned with vision :-
•1)Transduction
•2) Transmission of visual sensation
•3) Visual perceptions

31. transduction
•Rods & cones serve as a sensory nerve ending
for visual senasation
• Stimulus
inadequate adequate

32. Inadequate stimulus
•4 types of stimulus:-
•Pressure phosphane
•Movement phosphane
•Electrical phosphane
•Radiation phosphane

33. Adequate stimulus
•Visible portion of EM spectrum forms the
adequate stimulus
•Visible portion of light lies betnuvrays &
infrared rays
•Visible portion :-400 nm -750nm
•The visible consists of VIBGYOR ( 7 colours)

34. Transmission of visual sensetion
Photochemical changes take place
Light absorbed by rods and cones pigment
Electrical implusesare arise
Information is forwarded thuruganglion cells
Optic nerve
Optic chiasma
Optic tract
LGB
Optic radiation
Visual cortex

35. Visual perceptions
•Functional elements of vision
•1)light sense:-appreciation of light
•2)Form sense :-most acute at fovea
•3)Constrastsense :-differentiate bet
luminance which are not separated by definite
borders
•4) Coloursense :-discriminate betncolours

36. Photochemistry of vision
•Light falling on the retina is absorbed by rods
& cones , further photochemical changstakes
place
•It includes:-
•VitA
•Visual pigments
•Light induced changes

37. Vitamin A
(food) Dietary source of vitA
(Intestine) Digestion,absorption& transport
(Liver) 1.Storage of vitA 2.Production of retinol
in liver cells as binding protein
retinol
(Blood) Transport of retinol bound to retinol-binding
protein
(eye) 1.formation of 2.maintainance of healthy
rhodopsin corneal & conjunctivalcells

38. Visual pigments
•These pigments absorbs light
•The peak of each pigment ‘s absorption is
called its absorption maximum
Peak absorption
Wavelength (nm)
% of
aborption

39. Rhodopsin pigment
•Also known as visual purple
•Present in the outer segment of rods
•photopsin+ retinol Rhodopsin
•Rhodopsin protein is insoluble in water ; sensitive
to strong acids & alkalis
•Peak sensitivity : 493-505nm
•Absorbs yellow wavelength of light;transmitts
violet to red colour,hence appears visual purple

40. Cone pigments
•3 kinds of cone pigments
•These are different from rhodopsin pigments
•Responsible for colourvision
•Cone pigments are different from rhodopsin in
opsinportion;11 cisretinol is same as
rhodopsin
•Peak absorbance:-
•Blue sensitive cones:-435 nm
•Green sensitive cones:-535 nm
•Red sensitive cones:-580 nm

41. Light –induced changes
•Rhodopsin bleaching
•Rhodpsinregeneration
•Visual cycle
•Photochemistry of photopticvision

42. rhodopsin bleaching& regeneration
•
Rhodopsin
Barthorhodopsin
Lumirhodopsin
Metarhodopsin|
Metarhodopsin||
All trans-retinal
All trans -retinol
isomerase
11 cis-retinol
11 cis-retinal
opsin
NADH
NAD
NADH
NAD

43. Visual cycle
•Rate of photodecomposition = rate of
photoregeneration
rhodopsin
All trans retinal11 cis-retinal
opsin
Light energy
opsin

44. Photochemistry of photopicvision
•Like rhodopsin ,cone pigments also consists of
protein opsini.ephotopsin& retinine
•Photopsindiffers slightly from rhodopsin
•3 classes of photopsin:-
•Erythrolabe–red sensitive
•Chlorolabe–green sensitive
•Cyanolabe-blue sensitive

45. Thank You