ANATOMY & PHYSIOLOGY
KAINAT KHAN
• Retina is the innermost tunic of the eyeball
• Thin,delicate,transparent membrane
• Highly developed tissue of the eye
• Appears purplish red
Three distinct regions of retina:
1.optic disc
2.macula lutea
3.peripheral retina
• retina extends from optic disc to ora serrata
• Surface area:266sq/mm
• Pale pink in colour; well defined circular area
• Diameter: 1.5mm
• All the retina layers terminate here,except the
nerve fibre which pass through the lamina
cribrosa
 The lamina cribrosa (LC) is a sieve-like, mesh-
like structure located at the back of the eye,
specifically within the optic nerve head.
 It's made of collagen beams and allows the
retinal ganglion cell (RGC) axons and blood
vessels to pass through.
• The macula lutea is 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 :- photoptic
vision
• Fovea centralis is central depression in
macula;measuring 1.85 mm in diameter & 0.25
thickness
• It is most sensitive part of retina
• Diameter:- 0.35
• Central floor of fovea
• Umbo is the tiny depression in centre of
foveola
macula
Fovea
centralis
foveola
umbo
The peripheral retina can be divided into four
regions:
1. Near periphery
2. mid periphery
3. Far periphery
4. Ora serrata
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 fibre layer
10. Internal limiting membrane
• 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 bruch's
layer & loosely attached layer of rod and cone
cells
• Sub-retinal space :- potential space between
RPE & retina
•Retinal detachment :•separation of RPE from retina
Sub- retinal fluid :fluid between sensory retina & RPE
• Renewal of photoreceptor & recycling of Vit A
• Provides mechanical support to process of
photoreceptors
• Manufacturing of pigments absorbing light
• RPE cells are phagocytic
• Rods & cones transform light energy into nerve
impulses
• Rods contain photosensitive substance
rhodopsin whereas cones contain photosensitive
substance idopsin
• Cone cells - photoptic vision
• Rod cells – scotoptic
vision
• Cones :- 6.5 million
• Rods :- 120 million
• At fovea:max cones(199000cones/mm.sq) & rods are
absent
• Fenestrated membrane extending from the ora
serrata upto the edge of optic disc
• Processes of rods & cones pass through it.
• 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 foveal region
Outer plexiform layer
This layer is made of synapses between
the rod and cones with the dendrites of
bipolar cells.
• It is very thin & is similar to outer nuclear
layer
•It consists :Bipolar cells
Horizontal cells
Amacrine cells
Mullers cells
Central retinal vessels
Other glial cells
This layer disappers at fovea
• Consists of synapse between bipolar cell
& dendrites of ganglion cell
• Absent at fovea
• Consist of cell body & nuclei of ganglion cell
( 2nd order neurons)
• Absent at fovea
• Various types of ganglion cell.
• Consists of unmyelinated axons of ganglion
cells which converge at optic nerve head
• Thickness:- 0.5-2 um
• Thickness decreases from optic disc to lateral
side
• Fibres show definite pattern of arrangement
Consists of following elements:1) collagen fibrils
2) proteoglycans of vitreous
3) basement membrane
4) plasma membrane of muller cells
5) other glial cells
• Outer 4 layers :- choriocapillaries
• Inner 6 layer:- central retinal artery
• Fovea :- choriocapillaries
• Macular region:- superior & inferior temporal
branches of central retinal artery
• It is a complex phenomenon
• Main mechanism concerned with vision :• 1)Transduction
• 2) Transmission of visual sensation
• 3) Visual perceptions
• Rods & cones serve as a sensory nerve ending
for visual senasation.
• A process in which light convert into
electrical signals
Stimulus
inadequate
adequate
• Visible portion of EM spectrum forms the
adequate stimulus
• Visible portion of light lies between uv rays &
infrared rays
• Visible portion :-400 nm -750nm
• The visible consists of VIBGYOR ( 7 colours)
Light absorbed by rods and cones
pigment
Visual cortex
Photochemical changes take place
Optic radiation
Electrical impluses are arise
Information is forwarded thuru ganglion
cells
Optic nerve
Lateral
Geniculate Body
Optic tract
Optic chiasma
• Functional elements of vision
• 1)light sense:- appreciation of light
• 2)Form sense :- most acute at fovea
• 3)Contrast sense :• differentiate between luminance which are not
separated by definite borders
• 4) Colour sense :• discriminate between colours
• Light falling on the retina is absorbed by rods
& cones , further photochemical changes
takes place
• It includes:• Vit A (first molecule in the process of transforming
photons of light into electrical signals)
• Visual pigments
• Light induced changes
 These pigments absorbs light :
 Rhodpsin pigment:
pigment in rods
responsible for vision in night.
 Cone pigment : pigment in cons
responsible for vision in day light and
color vision .