There are 656 million people around the world who have colour vision difficulties. How do people with colour blindness see colour? How does colour vision work? Have you ever wondered how a dyschromatopsic sees traffic lights?
Human visual system
Contrast sensitivity tells us if we are capable of distinguishing shapes that have a luminosity similar to that of the background in which they are placed. It can be affected by different visual problems more significantly than visual acuity, so it is advisable to examine contrast sensitivity in order to have a better assessment of the visual quality of a person.