visual aid 
noun
1 (usually visual aids) An item of illustrative matter, such as a film, slide, or model, designed to supplement written or spoken information so that it can be understood more easily.For Neurath, visualization does not merely act as illustration; visual aids are ‘part of the explanation themselves.’...
- Mr Garwood became well known for his Sunday morning ministry at the bandstage, when he frequently introduced unusual visual aids to illustrate his sermons and talks to the children.
- Your meeting will typically include visual aids that illustrate the appropriate amount to eat.
2A device used to improve vision, such as a magnifying glass or glasses.Researchers are the University of Wisconsin have developed what is surely the weirdest visual aid ever: A device that lets the blind see - by using their tongues....
- Visual impairment may be helped with the use of glasses or other visual aids.
- Not so the directors of Ash Technologies, who certainly believe their portable visual aids for the partially sighted genuinely improve the lives of their users.