defective colour vision 1

Rena Mehta; Asstt Prof,Jaipur

EYE IS A WONDERFUL ORGAN WITH WHICH WE ENJOY THE BOUNTIES OF NATURE

IMAGINE A WORLD DEVOID OF COLOUR

COLOUR HAS ALWAYS FASCINATED US,

ON GROUND IN AIR

IN WATER

COLOUR CAN BE BROADLY DEFINED AS THE EFFECT ON THE

BRAIN OF AN OBSERVER WHEN AN OBJECT IS VIEWED IN PRESENCE

OF A LIGHT SOURCE.

74%

10%

16%

NORMAL PERSON

Colour blindness is the inability to distinguish certain colours.

It occurs when one or more of the cone types is missing or defective to any extent.

They may be absent entirely, or may be present, but unable to manufacture the necessary signals to the brain.

CONGENITAL ACQUIRED

CAUSES OF DEFECTIVE COLOR VISION

CLASSIFICATION OF

DEFECTIVE COLOUR VISION

Main type Sub type DEFECTIVE COLOUR SYSTEM

Trichromatic

Normal -

Protanomalous Red

Deuteranomalous Green

Tritanomalous Blue-yellow

Dichromatic

Protanopia Red

Deuteranopia Green

Tritanopia Blue-yellow

Monochromatic

SINGLE CONE VISION

LIMITED ROD BASED VISION

Red-green,blue-yellow

Red-green,blue-yellow

C LA SS IF IC AT ION OF DE FE C T IVE C OL OU R V ISION

N O R M A L D E U T R A N A M O U S LY

P R O T A N O M A L O U S T R IT A N O M A LO U S

T R I C R O M A T IC

P R O T O N O P IA D E U T R O N A P IA

T R IT A N O P IA

DI C H R O M A T IC

R O D C O N E

M O N O C H R O M A T IC

DE F E C T I V E C O L O U R V I S I O N

ANAMALOUS TRICHROMATES

ABNORMAL TRICHROMATS WHO ARE NOT DEFICIENT

IN RESPECT OF THEIR VISION OF ANY OF THE SPECTRAL COLOURS,

BUT HAVE AN ABNORMAL INCREASE OR DECREASE IN SENSITIVITY

IN CERTAIN REGIONS

Anomalous trichromatwith a shift in red sensitivity

PROTANOMALY

Anomalous trichromatwith a shift in green sensitivity

DEUTRANOMALY

Dichromats have two cone receptors rather than three, and match all the spectral hues

using two colour matching variables. There are three types of

dichromatism depending on which of the three normal pigments is missing.

Protanopes are the most common, lacking the long-wave ‘red’ sensitive receptors.

Deuteranopes lack the middle-wave ‘green’ receptors, and Tritanopes lack the short-wave ‘blue’ sensitive receptors.

Protanopes and deuteranopes cannot distinguish red light from green light,

while the rare tritanope has blue-yellow confusion2.

DICHROMATS

Available light without red.(red-insensitive dicromat) 

Green perceived as both red and green.

(red-insensitive dichromat) 

Available light without green.(green-insensitive dichromat) 

Red perceived as both red and green.

(green-insensitive dichromat

RELATING TO PROBLEM WITH RED RECEPTION

RELATING TO PROBLEM WITH GREEN RECEPTION

PROTAN

DEUTAN

PROTAN

DEUTAN

STANDARD

16 COLOUR PALETTE

STANDARD PALETTE PROTAN PALETTE

DEUTRON PALETTE

PROTAN PALETTE

DEUTAN PALETTE

Monochromats cannot discriminate colors and perceive only shades of gray.

Individuals with monochromatic vision are truly colorblind (achromatopsia).

There are two types of monochromats. Rod monochromats completely lack cones.

This condition is associated with reduced visual acuity, hypersensitivity to light (photophobia) and other vision impairments

Cone monochromats have only one cone type. They usually have good

visual acuity and none of the other vision impairments found in rod monochromats.

MONOCHROMATS

NORMAL VISION

ROD MONOCHROMATS CONE MONOCHROMATS

This condition is associated

with reduced visual acuity,

hypersensitivity to light (photophobia) and other vision impairments

They usually have good

visual acuity and none of the other vision impairments

found in rod monochromats.

INHERITANCE OF

DEFECTIVE COLOUR VISION

X Y XX

X X X Y X XX Y

WHEN FATHER HAS DEFECTIVE COLOUR VISION

X Y XX

X X X Y X XX Y

WHEN FATHER HAS DEFECTIVE COLOUR VISION AND MOTHER

IS A CARRIER OF RECESIVE CHROMOSOME

X Y XX

X X X Y X XX Y

WHEN MOTHER IS A CARRIER OF DEFECTIVE CHROMOSOME

X Y XX

X X X Y X XX Y

WHEN MOTHER HAS DEFECTIVE COLOUR VISION