Vision
Overview | Understanding vision | Visual functions (5) | Env. context | Design guidance (2) | Pop. stats. (2)
Visual functions
Introduction | Visual acuity | Contrast sensitivity | Colour perception | Usable visual field
With increasing age and various eye conditions, the usable field of view can change. This loss can either start from the centre of the visual field (central field loss) or from the outer edge of visual field (peripheral field loss).
The central visual field is used for focusing and perceiving detail. When the central field is obscured, tasks that require perception of detail (such as reading) become very difficult. People generally adapt to compensate for this loss and attempt to use the peripheral visual field. However, this part of the retina is less sensitive, resulting in a loss of acuity and contrast sensitivity. The same guidance given for acuity and contrast will help users with central field loss.
A reduction in the usable peripheral visual field results in tunnel vision and can affect mobility. A rail ticket machine with widely spaced controls can result in problems when viewed with a peripheral loss. The lower figures indicate a proposed redesign of the same machine where the continuity between the required action areas has been emphasised, resulting in a more usable interface.
A ticket machine that has poor clarity of layout viewed with normal vision, and the same ticket machine viewed with poor peripheral vision
This shows a redesigned layout for the same machine, which enables the overall layout to be perceived, even with a peripheral vision loss.
Overview | Understanding vision | Visual functions (5) | Env. context | Design guidance (2) | Pop. stats. (2)