Human vision and function/Part 2: Understanding vision: visual acuity, colour vision and 3D perception/2.2 Colour vision/Answers

1.	Why does staring at a red background cause you to see a green afterimage?

Because the centre-surround arrangement of retinal receptive fields is opponent for colour. 2.	List the primary colours of pigments.

Yellow, blue and red

3.	List the primary colours of light.

Green, red and blue 4.	If you mix all the primary pigment colours, what colour will you get?

Black 5.	If you mix all the primary colours of light you, what colour will you get?

White 6.	How did John Dalton explain his colour vision deficit and what was discovered in the 1990s about his colour vision defect?

''He thought that the fluids inside his eye were tinted blue. It was discovered that the green cone pigment in his eyes was missing''

7.	How common is colour blindness in men compared with women?

1 in 8 men or 1 in 50 women

8.	What is the effect if you have colour deficiency whereby one cone type is missing and what is this called?

''It results in you having only 2 cones with which to distinguish colour. This is termed dicrhomacy (or dichromat)''

9.	On which chromosome are the red and green photopigment genes located and what is the impact of this?

On the x-chromasome, this means they are x-linked and can exchange parts (recombine).

10.	What is the name of a commonly used test to check for colour vision problems?

Ishihara test for colour blindness.