Color Vision

ณวฒัน์ วฒันชยักิติกลุ ลีละวงค์

Visual process

light sourcelight

reflected light/color

object

eye

Electromagnetic spectrum

Visible light

normally visible light 400-700 nm

except : beta peak (380-400 nm) infant aphakic condition

color vision

how we can see all these colors?

AnaToMy

Visual process light pass through

cornea/AC/lens/vit absorption by the

rod/ cone photoreceptors

retinal neural circuit horizontal cells bipolar cells ganglion cells

optic nerve higher visual centers

LGB (parvocellular portion)

Cortex

Rod and Cone photoreceptors

Rod and Cone photoreceptors

<400 nm400-700 nm

>700 nm

Rod photoreceptors

92 millions (100M) no rod in central 0.25

mm of fovea peak at 5-7 mm from

foveal center decrease number with

age

Rod photoreceptors

mediate vision at low illumination levels (scotopic)

108 range of illumination from near darkness to daylight

critical flicker threshold 20 Hz

Cone photoreceptors

4.6 millions (5M) highest density at

macula stable numbers, no

relationship to age Mediate best vision

at daylight levels (photopic)

Cone photoreceptors Responsible for good

visual acuity and color perception

1011 range of illumination from moonlight nights to very very bright light

critical flicker threshold 55-60 Hz

Rods and Cones together Mesopic photopic + mesopic + scotopic = 1014 range of illumination

no rod in central 0.25 mm of fovea, peak between 5-7 mm from foveal center, while cone has highest density at macula

this distribution means midperiphery of VF the greatest lig

ht sensitivity (night vision) fovea high acuity, good color vision

Rod and Cone photoreceptors Rod 507 nm SWS cone (B-cone) 445 nm MWS cone(G-cone) 543 nm LWS cone (R-cone) 566 nm

Gene Encoding the Human Photopigments

Rhodopsin chromosome 3

Iodopsin (SWS) chromosome 7

Iodopsin (MWS,LWS) chromosome X

Cone cells L, M cones- very similar- dense hexagonal

packing- L/M ~ 2/1- all ~ 90%

S cones- longer inner segment- larger inner segment- deeper innervation- patchwork mosaic- low at fovea, peak 1

degree- all ~ 10%

genes : L, M cones

- located on chromosome X- tandem array ~ 2-6 (1 LWS, >1 MWS) hybrid

protan (red-blind) deutan (green-blind)

Horizontal cells1. H1 dendrite all cones-axon-rod2. H2 contact S cones avoid others3. H3 avoid S cones contact others

- local-circuit neurons- chromatic organization- opponent color coding first stage of wavelength discrimination ?

Bipolar cellsFor rod : on-cell type (single depol.)For cone : off and on-cell type

Depolarize (on) : depol. Response to central/direct illumination

Hyperpolarize (off) : hyperpol. To center illumination and depol. To surround illumination

Ganglion cells- Its axons form optic nerve and terminate at

LGB/ other diencephalic centers/ superior colliculus

- earliest visual neuron to generate true action potential

- neural coding in term of frequency of firing- spatial/color opponent organization- functional classification P & M

Ganglion cellsProperty P cells M cellscolor selectivity yes noreceptive field size small large (~10 timesluminance contrast low highcell size small largeconduction velocity low highresponse time course tonic phasicfunction in scotopic no yes number of cells 1,000,000 100,000

optic nerve LGB cortex/ other centers

Color vision11 basic color term

4 uniques hue : red yellow green blue3 achromatic color: blackblack white graygray

other 4 color :orange purple brownbrown pink

Basic Aspects of Color Vision

human can perceived 8000 colors at a single luminance level

at optimal cone vision (1000 luminance range) – 8,000,000 shades and tints can be distinguished

Theory of color reception

theory of trichromacy

theory of opponent color opponent cells double

opponent cells

Color vision : color system 1

CIE color systemCommission international del’Ecalirage specific luminance proportion x + y + z = 1 3 dimension 2 dimension spectral/non-spectral color white center

W.

Color vision : color system 2

Munsell color system- cylinder

- hue (spectral color) 10 x10 ( R Y G )- Circumferential

- value (lightness) up/down- chroma (whiteness) radial

Factors that modified color vision Brightness Saturation State of dark adaptation : Perkinje effect Adjacent cone : lateral inhibition Fatique and after image Optical factors : lens, macula, chromatic

aberration, Stile-Crawford effect

Colorless objects that appear colored

Blue sky : blue – easier scattered

Colorless objects that appear colored red sunset

Colorless objects that appear colored

blue water

Color Vision Defect

what is color?!?!?moo.o..o...

Color Vision Defects

Normal trichromats 92% Dyschromatopsia 8%

Classification of hereditary color defect

red green blueblueano. Trichromats Protanomal Deuteranomal TritanomalDichromats Protanope Deuteranope TritanopeMonochromats Blue cone monochromats Rod monochromatsRod monochromats

Dyschromatopsia Anomalous trichromatism

Protanomaly XR 1% Deuteranomaly XR 5% Tritanomaly AD 0.0001%

Dichromatism Protanopia XR 1% Deuteranopia XR 1% Tritanopia AD 0.0001%

Monochromatism Rod monochromatism AR 0.001% cone monochromatism XR UK

Congenital red-green defect most common male 8%, female 0.5% Cause

Deletion of R-G pigment gene Hybridization of R-G gene

Congenital red-green defect

Congenital red-green defect

Characteristics symmetrically binocular constant in type and severity

through out life normal VA/ fundus/ photoERG name the color correctly

HUE DISCRIMINATION DEFECT

Acquired color vision abnormality Characteristics

VA & VF defectGenerally varied in type and

severityUnstable severity

Acquired color vision abnormality

charateristics Affect one eye or asymmetrically

affect Use incorrect color name or

report that familiar color appearance has changed

Acquired color-vision abnormality

Kollner’ rule B/Y : retinal/choroid recept

or/outer plexiform R/G : neural disorder ganglio

n cell

Kollner’s ruleRetinal diseases : B/Y

Eg: RD, RP, ARMD, myopic degen, chorioretinitis, CRVO, DR, CSCR

Except : cone-dystrophy, Stargardt’s

Kollner’s ruleOptic nerve diseases : R/G

Eg: optic neuritis, ON compression, LHON, toxic optic neuropathy

Except : AD optic atrophy, glaucoma, AION, OHT

Acquired/hereditary color defect

characteristics- Color- naming- unilateral/bilateral- blue-yellow- change/ unstable- other visual symtoms

Color Discrimination

Hue Saturation (chroma) Brightness (luminance, intensity)

1. Hue Discrimination hue wavelength depend on proportion of cone output better in intersected sensitivity function cross point of pigment absorption

sensitivity yellow(590) red/green blue-green(490) green/blue

Hue Discrimination

1. HUE DISCRIMINATION

2.Saturation

color purity fully saturated color : only 1

wavelength for visible light desaturated color : add white light perception depth of color (dark/

light blue)

2. SaturationSaturation - how much of one hue must be add

to white to be distinguished- the more amount, the less

saturation- many variables purity, intensity,

size, time

2. SATURATION SENSITIVITY

yellow – lowest

saturation

3. Luminosityrelative brightness/lightness peak absorption photopic 555 scotopic 507 Purkinje shift (rod & blue

cone pathway?)

3. LUMINOSITY CURVE507555

Color vision tests

Color vision testsPatient selection- screening test in children, student,

worker- undiagnosed low vision- recent color disturbance- Family Hx of color defect- Occupations

Color vision tests Ideal color vision test

Detect the presence or absence of normal color vision

Distinguish between R-G and B-Y defect

Assess the severity of defect comfortable

Color vision tests1. Screening test2. Color discrimination test3. Color matching test

Color vision test 1: screening test

1.Color confusion1. Ishihara test2. FD15 test

2.Color saturation1. AO-HRR test2.TMC plate

Color vision test : Ishihara test

- Test R-G- High sensitivity

for congen R-G defect

Color vision test : AOHRR test

- 24 plates- Color

defect or not

- Assess severity (+/-)

- R-G and B-Y

Color vision : FD-15- Farnsworth D-15

- line of confusion- R/G,B/Y- separate color handicap

FD-15

FD-15

Color vision tests1. Screening test2. Color discrimination test3. Color matching test

Color vision test 2 : discrimination Hue discrimination

FM-100 Farnsworth desaturated panel D-15 Lanthony new color test

Lightness discrimination Verriest’s lightness discrimination

Saturation discrimination Sahlgren’s saturation test

Color vision test 2 : discrimination ใชเ้วลามาก อาศัยความชำานาญ ไมเ่หมาะกับ routine exam ไมเ่หมาะกับเด็กอายุน้อยกวา่ 10 ปี

Farnsworth-Munsell 100 hue test

- 85 caps in 4 groups- hue discrimination test- serial color order within 2

min /each group- position&number of error

score

FM 100 hue test

Goals Grading of color discrimination in

normal subjects (superior/ average/ low)

Find zone of color confusion

Farnsworth-Munsell 100 hue test

Color vision tests1. Screening test2. Color discrimination test3. Color matching test

Color vision 3 : matchingAnomaloscope1. Nagel R/G

red640 + green545 = yellow5892. Pickford-Nicolson B/Y, R/G3. Sloan’s achromatopsia test

grading severity Expense

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