Visual impairment - moderate . Visual impairment - severe .
Many telephones use small text displays that show dark characters on a mid-tone background.
This is very difficult to read for most people with low vision. It is very important to display text and numbers in a way that provides maximum contrast between the characters and the background. Pale colours and colours which are close in tone should be avoided. White or yellow type on black or a dark colour is more legible provided that the typeface weight and size are suitable. Small type and very bold type tend to blur for some people, reducing legibility.