Abstract
This chapter explains vision and visual perception in order to provide a basis on which information systems can be based. In the first section on vision the structure and function of the eye, visual acuity, adaptation, ageing, colour blindness, night blindness, night myopia, cataract, aniseikonia and anisocoria are discussed. The second section considers visual perception. Some examples are given of the way in which the processing of visual information may be subject to optical illusions. Perceptual problems in driving are considered including expectancy and perceptual limitations. In the latter category the problem of the assessment of relative speed is found to be particularly common.