VSP3 Color Vision 4 a and 4 b

Inherited Color deficiency presents...

- early on

- not progressive

- typically bilateral

- about 4.5% of the population

Prevalence of Red Green CD

1 in 12 males

1 in 200 females

Prevalence of Blue Yellow CD

equal in males and females

1 in 10,000

Blue cone monochromacy

Males >> females

1 in 100,000

Acquired CD is assocaited with

- Ocular disease (retina or ON)

- systemic disease

- drug toxicity

- Chemical exposure

- COrtical impairment

- TBI

Dichromacy

the anopias

Missing 1 of the 3 photopigments

anomalous trichromacy

the anomalies

3 cone photopigments are present

Types of Dichromacy

Deuteranopia

Protanopia

tritanopia

Deuteranopia

chlorolabe is missing

Protanopia

Erythrolabe is missing

tritanopia

Cyanolabe is missing

Dichromats have ____ number of cones

the same

therefore goof visual acuity

Replacement Model of Dichromacy

Photopigment is replaced by the remaining photocpigements

Blue cone monochromacy

x liked ancromatopsia

MWM cones and LWS cones not funciton

poor va

Photopobia

Poor or no color disciminaiton

Nysrtagmus

Myopia

Abnornmal Photopic ERG

- SWS and Rods normal

Normal Scotopic ERG

Stable and present at broth

Anomalous trichromacy

Three photopigments are present, but the absorption spectrum of one of these photopigments is displaced

The greater the displacement the

more severe the color vision defect

Deuteranomalous Trichromacy

Chloroble (Green) displace toward longer wavelengths

Protanomalous trichcomacy

Erythrolabe displaced toward shorter wavelengths

The most common color deficiency

Deuteranomaly

In Deuteranomaly ____ cone functino is normal

LWS

Normal difference btw M and L cone peak is

25 nm

In Deuteranomaly

MWM cone function is shifted

to the right toward the LWS cone

by almost 20 nm

Now <10nm between M and L cone peak absorption

Can someone be a deuternanomalous drichromat?

NO

Deutan Protan or tritan

are general and can refer to either dichromacy or anomalous trichromacy

Deutan or Protan deficits confuse

red and green

Red Green color anomalies

includes:

Deuteranomaly

Protanomaly

Deuteranopia

Protanopia

Usually inherited

!!!!!Exam

Tritan defecitst confuse

Blue and Yellow

Include Tritanomaly annd tritanopia

usually acquired but not alwaus

How are anopias and anomalies different than typical trichromats?

differences in:

- Spectral Sensitivity

- wavelength discrimination

- Color confusion lines

- perception of saturation

1. Spectral Sensitivity: Chromactic System

Spectral sensitivity of the 3 cone pigments:

Cyanolabe 426 nm SWS

Chorolabe 530 nm MWS

Erthrylabe 557nm LWS

Color Opponent Sepctral Sensitivity Curve:

In normal trichromacy

- discplacement of the sepctral sensitivity

- due to color opponency of M and L cones

- Now peak at 520 nm and 620 nm (dont memorize)

- remain 3 peaks

With dichromats we see

2 peaks seen

Spectral sensitivity: Luminance Function for normal trichromacy

Luminance Function peaks at 55nm

wit input from M and L cones

Luminance function in Dichramacy

the curve shifts left or right depending on type of deficiency

Protanompia overall luminance funciton is displace toward

shorter WL (left)

Deuteranopia overall luminance fucntion displaced

VERY slightly toward longer wavelengths (right)

almost normal in appearance !!!

There is a bigger shift in the luminance function curve when the

long wavelength cones are missing

The LWS play a stronger role in overall Luminance function

Which condition shows a very little change in luminance function compared to normal trichromats?

Deutreranopia

Which cones play a larger role in generating the photopic luminance curve

LWS cones

For protanopes (LWS are missing)

Since 680 nm are not absorbed as well what happens to their perception

What will a person with protanopia have difficulty doing?

Picking out the best meat in the grocery store

(decrease sensitive to red)

Luminance: What happens in anaomal trichromats?

- same discolation

- less pronounced

Luminance: Protanomaly

same dislocaiton toward shorter wavelengths but less pronounced

Lumiance deuteronmaly

same dislocation toward the longer wavelengths but less pronounced

2. Wavelength Discrimination

Normal Trichromatic best wavelength discrimination on W curve

495 nm and 590 nm

less than 2 nm

Wavelength Discrimination in Protanopia and Deuteranopia

poorere througout the spectrum

best at 490 and 495nm

Wavelength Discrimination in Protanopia and Deuteranopia: Longer wavelengths ...

have no ability to discriminate based soley on wavelength

this is because they have only 1 cone pigment at longer wavenths (>530nm or 545nm)

monochromatic color mathing

Protanopia and Deuteranopia are just like monochrats at wavelengths greater than

545nm

When monochromacy is present - discrimination is possible based ipon

luminance and the luminosity curve

SEE GRAPHS PLS

tritanopia well discrimaintion at _____ wavelengths and poor discrimination at ____ wavelegnths

longer

shorter

3. Color Confusion Lines

On CIE sufficient change in color in any direction are seen as

differnt for a normal trichromat

Colors that dischroamts cannot distinguish lie along

straight lines on the CIE diagram

CONFUSION LINES

For trichromats: colors that lie along confusion lines have

changing quantal absoprtions in one of the three cone pigments

the remain 2 cone types remain constant

Color confusion lines defition

the loci of colors in the CIE that appear identical to the dichromat

Copunctal point definition

the point where the color confusion lines convere and meet on the CIE

convergence point

Protanopes Copunctal point is close to

700nm

tritanoes Copunctal point is close to

400 nm

Deutreranpes copunctal point is

outside the CIE diagram

The color at each copunctal point is considered

imaginary

Protanopes and Deuteranopes share a confusion line _____ to the spectral locus from ______, this means

parallel

from 540 to 700nm

they both cannot distinguish among monochromatic lights from the middle to long wavelength end of the spectrum

Green, Yellow, Orange, Red are confused (Red Green Deficiency)

If a person confuses wavlengths along the spectral locus of 530 and 690, this means they have

Protan or Duetan but we cant tell which type

Color Confusion Lines: tritanopes

do not share confisin lines

5. Perception of Saturation

trichromat: A monochromatic light at ____ appears less saturated than. a monochromatic light at any other wavelength

570 nm

Protanopia: A monochromatic light at ____ appears less saturated than. a monochromatic light at any other wavelength

492nm

appears white!

Deuteranopia: A monochromatic light at ____ appears less saturated than. a monochromatic light at any other wavelength

489 nm

appears white!

Neutral Point

a spectral wavelength that a dichromat selects to match a specified white light

the WL on the spectral locus is called the neutral point and is confused with white

all stimulus falling on the confusion line through the neutral point are also confusion with white

Perception of Saturation Anomalous Trichromacy

No neutral points!!!

Beyond 545 nm

Protanopes and deutranopes are monochromats

They can however label colors from brightness and conext

What colors do dogs see

blue and yellow