Table 2

Components of visual function and impact on everyday life

Components of visual functionDefinition of outcomeExamples of the impact on everyday life discussed in the focus groups
Distance visionA patient’s ability to see objects/people clearly from distance (beyond arm’s length).Difficulties in seeing faces, number plates, road signs, cars (only see the headlights), reading the guide on the television.
Near visionA patient’s ability to see near objects.Difficulties in seeing the remote control, phone numbers, menus, coins, the writing on a bottle of the shampoo; missing certain parts of text when reading.
Colour visionA patient’s ability to distinguish colours accurately.Difficulties in differentiating colours (eg, blues and yellows) or choosing items of clothing that match.
Peripheral visionA patient’s ability to see towards the edge of their vision.Difficulties in seeing items in the periphery of their vision.
Contrast sensitivityA patient’s ability to distinguish objects from the background.Difficulties in dealing with different contrasts between light and dark, for example, having to wear sunglasses on a foggy day.
Depth perceptionA patient’s ability to perceive the world in three dimensions.Difficulties in judging distances (eg, estimating how far away or how high a step is).