COLOUR

VISION
Presenter: Dr. Hazirah binti Mohd Marzuki
Supervisor: Encik Ahmad Sharmizi
Outline
• Definition
• Physiology of colour vision
• Theories of colour vision
• Factors affecting colour vision
• Types of colour vision defects
• Congenital vs acquired colour blindness
• Tests for colour vision
Introduction
Colour vision
• Ability of humans or animals to perceive differences between light - composed of
different wavelengths independently of light intensity.
 Colour Perception
• Visual system process
• Mediated by a complex process between neurons
• Begins with differential stimulation of different types of photoreceptors by light
entering the eye: ROD
ROD & CONE
CONE

• ROD
Rods : Scotopic/ night vision & vision in shades of gray.

• CONE
Cone : Photopic/ daylight vision, colour vision & acuity of vision.

• Those photoreceptors then emit outputs that are then propagated through many
layers of neurons and then ultimately to the brain
 RODS
Rods CONES
Cones
• High sensitivity: for night vision • Lower sensitivity: for day vision

• More sensitive to scattered light • More sensitive to direct axial

rays

• More photopigment • Less photopigment

• Slow response, long integration • Fast response, short integration

time time

• Low acuity: not present in • High acuity: concentrated in

central fovea central fovea up to 20-30 degree
of fovea

• Achromatic: one type of rod • Chromatic: 3 types of cones

pigment ( Rhodopsin )
( Iodopsin )
 • Light is detected by rod cells of the retina.
SCOTOPIC • Rods are maximally sensitive to wavelengths near 500 nm, and play little role in color vision.
VISION

• Light is detected by cone cells

• Responsible for color vision.
Photopic
• Cones are sensitive to a range of wavelengths, but are most sensitive to wavelengths near 555 nm.
vision

• in between Scotopic & Photopic

Mesopic • both rods and cones provide signals to the retinal ganglion cells.
vision
Peak sensitivity of scotopic vision is ~ 507 nm and photopic vision is ~ 555 nm.
 Light
LightDispersion
Dispersion

• Visible light (white light) consists of a collection of component colors and often
observed as light passes through a triangular prism
• Upon passage through the prism, the white light is separated into its component
colors - red, orange, yellow, green, blue and violet.
• The separation of visible light into its different
colors is known as dispersion.
• Each color is characteristic of a distinct wave
frequency; and different frequencies of light
waves will bend varying amounts upon passage
through a prism
Normal colour attributes
• Any colour has: HUE, LIGHTNESS & SATURATION.

• HUE Dominant spectral colour is determined by the

HUE
wavelength of particular colour
- colour that is red, yellow, blue etc.

• LIGHTNESS
LIGHTN Bright or pale. Depends on the luminosity of the
component wavelength

•SATURATION
SATURA Degree of freedom from dilution with white.
Physiology of colour vision
• Cone: 11 cis-retinal + photopsin
• Cone pigments sensitive to photons of light generated within specific
wavebands
• Few differences in amino acid sequence in the three cone opsins 
account for peak wavelength sensitivity
• 3 types -sensitive to three different spectra
• Resulting in trichromatic color vision.
• Conventionally labeled according to the ordering of the wavelengths of the
peaks of their spectral sensitivities:
• short (S), medium (M), and long (L) cone types.
• However, these three types do not correspond well to particular colors (RGB)
• Photochemical changes in cone pigments  cascade of biochemical
changes  produce visual signal : cone receptor potential
• Action potential in photoreceptor  electrical conduction  synapse
of photoreceptors, bipolar, ganglion and amacrine cells
Horizontal cells
• 2 completely different kinds of response:
• Luminosity response : hyperpolarizing response with broad spectral function
• Chromatic response : hyperpolarization for part of spectrum and depolarizing
for remainder
Bipolar cells
• Centre- surround spatial pattern:
• Red striking centre : hyperpolarization
• Green light in surrounding : depolarization
Ganglion cells
• Colour coding : 3 distinct group of ganglion cells with different function : W,
X and Y
• X: mediated colour vision
• Can be stimulated by single/few cones:
1. All 3 types of cones stimulate the same ganglion cell  resulting signal is WHITE
2. Opponent colour cell:
• Some GC excited by 1 colour type(red) and inhibited by another (green)  successive colour
contrast
• 3 main types of colour opponent in ganglion cells:
i. ON-centre Red/OFF-centre green
ii. ON-centre blue/OFF centre yellow
iii. ON centre white/OFF-centre black : receive input from all 3 cones and in which colour mixing
occurs
3. Double opponent colour cell
• For both colour and space
• Concerned with simultaneous colour contrast
• Have a receptive field with a centre and surround
• Response may be ‘ON’ to one colour in centre, while ‘OFF’ to it in surround
• Indicates the process of colour analysis begins in the retina and not entirely a
function of the brain
Retina
• Trichromatic colour vision extends 20-30 degrees from point of
fixation
• Peripheral to it - red & green are indistinguishable
• Far periphery - all colour sense is lost though cones are still in this
region
• Very centre of fovea (1/8 degree) – blue blind
Lateral Geniculate Body
• All LGB neurons carry info from more than 1 cone cell
• Colour information: relayed from ganglion cell  parvocellular portion of
LGB
• Spectrally non-opponent cells which give the same type of response to any
monochromatic light constitutes 30% of all LGB neurons
• Spectrally opponent cells make 60% of LGB neurons
• These are excited by some wavelength & inhibited by others, thus carry colour
information.
• 4 types:
• Red and green antagonism : +R/-G
• Red and green antagonism: +G/-R
• Blue and yellow antagonism: +B/-Y
• Blue and yellow antagonism : +Y/-B
Striate Cortex
• From LGB  layer IVc of striate cortex (area 17)  blobs in layer II &
III (centre surround cells)  thin strips in visual association area 
specialized area concerns with colour :

Lingual and Fusiform Gyri of

Occipital Lobe
Theories of colour vision

Trichromatic theory

Opponent colour theory

Trichromatic theory (Young Helmholz &Maxwell)
• Existence of three kinds of cones.
• Each cone containing a different photopigment & sensitive to one of three
primary colours
• Red
• Green
• Blue
• Perceived colour depends on relative summation
of each class of cone (unequal stimulation of 3
types of cone)
• Concludes that blue, red and green are the
primary colours
Trichromatic theory
RED SENSITIVE CONE PIGMENT
 Known as ERITHROLABE.
 Long wavelength sensitive cone pigment.
 Absorbs maximally in a yellow position (peak 565 nm).
 Spectrum extends far enough to sense red

GREEN SENSITIVE CONE PIGMENT

 Known as CHLOROLABE.
 Absorbs maximally in a green position (peak 535 nm).

BLUE SENSITIVE CONE PIGMENT

 Known as CYANOLABE.
 Short wavelength sensitive cone pigment.
 Absorbs maximally in a blue-violet position (peak 440 nm).
Opponent Colour Theory (Hering)
• Based on receptive field organisation of ganglion cells
• 3 colour opponent arrangement:
• Red-Green
• Blue-Yellow
• White-Black

• Certain colour pairs are mutually exclusive

and do not mix
• Refines spectral sensitivity of ganglion cell
response, so perception of hues &
unsaturated colours
Opponent Colour Theory (Hering)
• Opponent cells: simple receptive fields: their firing is stimulated by one colour
and inhibited by another colour

• Double opponent: centre-surround visual

field.
Centre stimulated by one colour and
inhibited by another colour. Surrounding
area has opposite properties. Suited for
identifying object borders and contrast
Factors affecting colour vision
• Location of the retina tested. 30 degrees from fixation, periphery to
this, red and green become indistinguishable, far periphery colour
sense is lost
• Illumination
• Presence of pigments
• Lens absorption . Young vs older
• Functioning cortex
Colour vision defects
• Trichromate: individuals with normal colour vision.

• Colour blindness: inability to seeing red, green, or blue or mix of these colour.

• Anomalous: if there is a weakness of particular colour.

• Anopia: complete absence of colour perception.

• May be congenital or acquired

 CONGENITAL COLOUR BLINDNESS
 Cause:
 Usually genetic condition from parents – X-linked recessive
 Gene for rhodopsin - chromosome (3)
 Gene for blue sensitives cone pigment - chromosome (7)
 Gene for red & green sensitive cone pigment - on X chromosome
 Condition stable throughout life.
 Males: 6-8%, females 0.4%

Congenital colour
Colour confusion due to blindness
deficiency of mechanism
to perceive colour
Dyschromatopsia Achromatopsia

Anomalous
Dichromatic
trichromatic
 Dyschromatopsia

Anomalous
Dichromatic
trichromatic

Faculty to perceive one of the three primary

Mechanism to appreciate all 3 primary
colour is completely absent
colours present, but defective

Protanopia Red blindness

Protanomalous Red weakness

Deutranomalous Green Deuteranopia Green blindness

weakness

Tritanomalous Blue weakness Tritanopia Blue blindness

**Nopia in the end of the word means blindness,

**Nomaly means = weakness
Prot = RED , Deuter= GREEN , Trit=BLUE
Achromatopsia
• Extremely rare
Achromatopsia

Cone
monochromatism Rod monochromatism

- Total colour blindness and day

blindness
Presence of only one primary
colour  truly colour blind - VA usually ~6/60
Usually has VA 6/12 or better - Nystagmus
Fundus normal
 ACQUIRED COLOUR BLINDNESS
• Secondary features of variety of pathological states
• Changes on pre-receptor, receptor and post-receptor
mechanisms that affect the perception of light stimuli
• May follow damage to macula or optic nerve

B-Y Retinal lesions such as CSR, macula

impairment oedema, shallow RD

optic nerve lesion optic neuritis, Leber’s

R-G deficiency
optic atrophy and compression of ON
• ::
increased sclerosis in crystalline lens
Blue blindness
(cataract)
Congenital VS Acquired
CONGENITAL ACQUIRED
Affects both eyes equally One eye only OR asymmetric
Usually R-G defect B-Y OR R-G
Other visual functions normal Other visual functions abnormal
Stable through lifetime Variable, depended on test and diseases
conditions
Learned to adapt – can label objects Cannot name colour correctly
More prevalent in male Equally prevalent in male and female
No associated disease or toxicity Classification not straightforward with
standard clinical colour test
COLOUR VISION DEFECTS

Most commonly red/green

8% of males, 0.5% of females.

Females tend to be carriers- have normal colour

vision.

Affects colour discrimination, colour matching & career

choices.
 TEST FOR COLOUR VISION
Objectives of the tests
• Sreening test: Identifies subject with defective colour Pseudoisochromatic
plates
vision from normal. Eg: Ishihara test

• Quantitative/Grading test:Assess severity of colour FM 100-hue test

deficiency (mild/moderate/severe).

• Qualitative/Classifiying test: Diagnose type of colour

blindness (protan/deutan/tritan). Anomaloscope

• Vocassional test : Identifies colour matching ability, hue

discrimination & colour recognization, stimulate Lantern test
environment encountered by the job
 TEST FOR COLOUR VISION
• Precise or exact color matching industries:
• Textiles, foods & beverages, garments, paints and others.
• Career / Profession / Social
• Armed forces
• Aviation
• medical professional
• Pharmaceutical
• electric & chemical
• Maritimes
• commercial driving
• railroad
Type of Tests

• Pseudoisochromatic Test Plate

• Hue Discrimination / Hue Arrangement Test
• Color Matching / Mixing
• Color Naming / Sorting
Pseudoisochromatic plate test
• Most commonly used tests, easily and rapidly administered
• Colored symbol made up of colored dots of varying sizes embedded in the
background of differently colored dots.
• The figure and the background colors are chosen so that they are confused by the
deficient but discerned by normal
• Designed to screen for the presence of red-green inherited colour vision defects
• Eg:
1. Ishihara plates
2. American Optical Hardy-Rand-Rittler (AOHRR) Plates
3. Standard Pseudoisochromatic plates
Ishihara test
• The most common test used.

• Can test for red/green colour blindness but not blue colour blindness.

• Most likely to be used for routine colour vision screening in schools or medical.

• This test contains of circles created by irregular coloured dots in two or more
colours.
Ishihara test
• Comes in three different forms: 16 plates, 24 plates and 38 plates
(10th edition)
• Plates should be held at 75cm under good illumination
• Numerals should be answered in not more than 3 seconds
• Pathway tracing should be completed within 10 seconds
• Designed in four ways:
• 1st plate : for demonstration and
malingerers
Demonstration plates
• A quick colour blindness test

Both normal and those

with all colour vision
deficiencies should read
the number 12
Transformation plate
• Plates 2-9
• A number seen by a colour normal appear different to colour
deficient subject

Normal person
read this as 74
whereas red-green
colour blind person
will read this as 21
Vanishing plate
• Plate no 10-17th
• A number is seen by a colour normal but cannot be seen by a colour
deficient subject
• Normal colour vision should
read the number 5

• Red-Green colour deficiencies

should read the number 2

• Total colour blindness should

not be able to read any
number
Hidden Digit Plates
• Plates 18-21st
• Normal person does not see a figure while a colour vision defect will
see the figure
• Normal colour vision and those
with total colour blindness should
not be able to read any number
• Majority of those with red-green
deficiencies should read the
number 5
Diagnostic Plates
• Plates 22-25th
• Seen by normal subjects, colour vision
defects one number more easily than
another
• Protans only see the number on the
right side and deutans only see the
number on the left.
• Normal person read as 42, red colour
blind person read as 2 while green
colour blind person read this as 4
Ishihara Test Plate
• Scoring/Interpretation
• Pass or Fail
• Count no. of plate misread (exclude the demo plate)
American Optical – Hardy Rand Ritter
(AOHRR)
AOHRR
• Similar principle with Ishihara
• Content:
• Screening Plates
• 4 Demo plates
• 6 Vanishing plates –2 for Tritan and 4 for R-G defect
• Diagnosis & Severity Plates
• 10 plates for diagnosis and severity
• Scoring and interpretation:
Hue Discrimination Test
• Color caps of different hue to be arranged in serial order of hue.
• Qualitative test
• Can not distinguish between Dichromats and Anomalous Trichromats.
• E.g.: Farsnworth Munsell D15, FM 100 Hue
Farsnworth Munsell D15
• Set of 16 colored caps with reference number inside it.
• With 2 fixed reference caps.
• Because of large different color of adjacent caps therefore it evaluates
major color confusion of severe RG or BY defect.
• Usually indicates after fail the Ishihara.
• Guidelines:
o Illumination : Daylight
o VA : not more than 6/60
o Test distance : 50cms
• Scoring/Interpretation
oBy plotting the result into
connection dots diagram.
oCompare it with the defect axis.
Example of Deutan pattern.
FM 100 HUE
• An expanded version of D15
• Consist of 88 colored caps, separately in 4 boxes.
• Each boxes has 2 fixed reference caps.
• Main aim is to classify and to assess its severity.
• Also can be used to assess progression of acquired CV defect.
• Guidelines:
o Similar to D15
• Scoring/Interpretation
o Caps arrangement can be plotted in
its software.
o Refer the pattern according to the
defect axis
o Total Error score for type of
discrimination
Normal
Protan
Deutan
Tritan
Color Matching / Mixing Test

• One reference color to be matched by mixing 2 colors ( Red& Green)

• E.g.:
o Anomaloscope, City University Test
Anomaloscope
• Type:
o Nagel Anomaloscope
o Pickford Nicholson Anomaloscope
o NeitzOT Anomaloscope
• Subject need to mix red and green into a proportion that matches the
reference Yellow
City University Test
• Consist of 10 plates.
• Each plate contains 1 reference dots at the center & 4 peripheral
colored dots.
• Patient/subject needs to select peripheral colored dots that closely
matches the center colored dots.
Color Naming / Sorting Test
• Subject/patient needs to name or sort out the color
• Not popular
• E.g.:
o Farsnworth Lantern Test
o Yarn (Holmgren-Wools Test)
Lantern Test

• To name the signal

light
• Brightness can be
adjusted
Yarn Test
• To select from piles of
colored yarn that matches
the “standard skin”

• Not effective for diagnosing

purpose.
Thank You.