Unit 2 - Colour Vision Flashcards
What colour do you see when all spectral colours are added together?
White
What colour to do you get when all pigment colours are added together?
Black
What does Hue describe?
Specific wavelength
What does saturation describe?
The intensity of colour
What term described the intensity of the light being emitted?
Brightness
What is the peak sensitivity of the cone system?
555nm
What is the peak sensitivity of the rod system
500nm
What phenomena describes red roses looking black in twilight?
Purkinje shift
What photoreceptors would you have if you had rod monochromacy?
Only rods
what photoreceptors would you have if you had cone monochromacy?
Rods and only one set of cones
Which cones do you lack if you have protanopia?
Long wavelength cones i.e. red
Which cones would you be lacking if you had deutranopia?
Medium cones or green cones
Why are red/green colour deficiencies more common?
They are on the X chromosome
Where is S-cone opsin encoded genetically?
chromosome 7
what is hering’s opponent colour theory
Idea that we have three opposing colour pairs blue/yellow, red/green and black/white. Explains after images. Activation of one pair leads to inhibition of the other in the pair.
What does trichromatic theory of Young-Helmholtz fail to explain?
The perception of black
What is Kollner’s rule?
Roughly explains colour vision anomaly by position of retinal problem.
According to Kollner’s rule which defects would cause blue/yellow defects?
Media and outer retina
According to Kollner’s rule which defects would lead to red/green defects?
Inner retina and pathway issues e.g. optic atrophy, toxic amblyopia and pathway lesions
Verriest classified colour vision defects into type 1,2 and 3. To which does each type correspond?
Type 1 - protan like
Type 2 - deutran line
Type 3 - Tritan like
Which colour vision test is useful in MR clinics and why?
Hardy, Rand, Rittner because is can still be used with v/a down to 6/60
What v/a do you need to use Isihara colour vision tests?
6/18
What is the definition of colour?
The sensation that allows us to discreminate uniform surfaces of equal brightness.
