DEUTERANOMALYPersonal experience of a specimen of Homo sapiens

and a little scientific background behind it

Jan Stanik15/7/2014

WHAT IT IS1 most common colour vision deficiency in males

2 impaired ability to recognise red-green hues

3 inherited and linked to X-chromosome

4 mutation of pigment in retinal cone cells

males females

WHAT IT IS NOT1 special in males

• remember, 5% male population, 0.35% female population • due to being X-chromosome linked

2 colour blindness

3 disease

2 curable

• colour vision deficiency is the preferred term• colours are recognised

JOHN DALTON1 had deuteroanopia

• dichromatic: only red and blue photoreceptors• first paper on colour blindness

2 daltonism

3 1794 Extraordinary factsrelating to the vision of colours

• adopted as general form for impaired colour vision

“that part of the image which others call red appears to me little more than a shade or defect of light. After that the orange, yellow and green seem one colour which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow”

1776-1844

HOW YOU KNOW1 people around you notice

• your wife will definitely notice• not that prevalent in female population

2 after having yourself tested

3 two exactly same fruits taste differently

4 yellow is actually green

• any GP can do the test (likely variant of Ishihara Test)• to lesser degree of accuracy can be done online• mandatory for certain professions• mandatory in certain countries for obtaining a driving license

5 magenta is also green

SHINOBU ISHIHARA

2 designer of Ishihara Test• 1917, 50 years before studies of photopsins• basic 24 watercolor plates, 37 plates full test• his assistant was a colour blind• symbols originally used Japanese script Hiragana

1 Japanese army surgeon

1879-1963plate № 1, displaying number 12visible to person with deuteranomaly

plate № 11, displaying number 6invisible to person with deuteranomaly

PHOTON1 eye receives information as rays of photons

• input from environment is transduced in eye

2 particle travelling at speed of light

3 frequency is colour

4 frequency is wavelength

• it is de-facto light• massless

5 colour ≡ wavelength

f = c/λf: freq

uency

c: speed of li

ght (299 792 458 m/s)

λ: wavelength

• frequency is the energy of photon• objects in environment emit/reflect photons of different frequencies based on their surface chemical composition (red surface emits red photons)

VISIBLE SPECTRUM1 390 – 700 nm

• frequency range: 790 – 430 THz

2 recap: color ≡ frequency ≡ wavelength

390 nm790 THz

700 nm430 THz

CONE CELLS1 one kind of photoreceptors cell in retina

• the other 2 being rods and photosensitive ganglion cells• neuron – has synaptic connection to visual cortex

2 responsible for color vision

3 activated at brighter light

4 3 subtypes

5 different pigment in each subtype

• rods are activated in low light intensity (night vision)

• in deuteranomaly sensitivity of opsin in M-cones is closer to that of L-cones• photopsin (protein) is attached to retinal (vitamin A) to form pigment• retinal is the same, cells differ in photopsin type

CONE CELLS SUBTYPES

L-coneM-coneS-cone

photopsinOPN1SW

Peak sensitivity420 – 440 nm

OPN1SW

photopsinOPN1MW

Peak sensitivity534 – 545 nm

photopsinOPN1LW

Peak sensitivity564 – 580 nm

CONE CELLS IN RETINA1 very few S-cones, 1/10 of M- and L-cones

2 no S-cones in fovea

ratio of conecells in retina

COLOUR VISION1 several cones receive stream of photons

• photons in stream have same or very similar wavelengths (colour)

2 pigment in each cell gets activated

3 hyperpolarised at rest

4 3 signals generated

• signal is carried by sodium ions Na+

• in absence of light signal is not generated• noiseless system

• protein changes shape of retinal• neurotransmitter flow into the cell is reduced

COLOR VISION1 difference in stimulation of each cell type

• three measures are calculated

brightness = R + GR: signal from L-cells

G: signal from M-cells

color1 = R - G color2

= B – brightness

B: signal from S-cells

2 model situation: 2 colors

437 nm 533 nm 564 nm

different signal delta

DEUTERANOMALY1 M-cone sensitivity range shifted towards L-cones

2 signal differences in part of spectrum distorted

437 nm > 533 nm 564 nm

3 red-green hues sensitivity impaired

indistinguishable signal delta

GENETICS1 L-cones and M-cones are evolutionary close

• theory that one evolved by mutation of the other

2 sequences for photopsins in X-chromosome

3 males have only one X-chromosome

4 females have two X-chromosomes

• 19 chromosomes and 56 different genes involved in colour vision

5 in general mother is only carrier

• if color vision genes are abnormal they result in color vision anomalies

• if color vision genes in one are abnormal the other takes over• color vision deficiencies less prevalent in females

IMPAIRMENT1 no

2 unless for professionals, such as graphic designers, printers, etc.

3 disqualified for driving license in some countries

RESOURCES1 Ishihara Test

http://www.dfisica.ubi.pt/~hgil/p.v.2/Ishihara/Ishihara.24.Plate.TEST.Book.pdf

2 Online Daltonism Testhttp://www.opticien-lentilles.com/daltonien_beta/new_test_daltonien.php