In addition to its well-known capacity for light and dark adaptation the eye also adapts to colour (colour adaptation or chromatic adaptation). For example, a white sheet of paper always has the same white appearance regardless of whether we look at it in daylight or in artificial light. In reality, however it has a blue hue in daylight and a yellow hue in artificial light. The reason why we always see it in the same colour is that our eyes adapt to the ambient light conditions (chromatic adaption).
This adaptation to colour can also occur during a colour perception test designed to detect colour blindness. Prolonged gazing at a colour perception test such as the Ishihara plates can therefore lead to distorted results. To avoid this the examinee is shown the plates for only a few seconds, followed by a white screen. This moment is indicated to the examiner by a grey cross appearing on the screen above the colour plate just shown. The examinee can still select the appropriate answer after the plate has disappeared. The default presentation times in the Binoptometer® 4P are as follows:
Ishihara colour plates: 4 seconds
Velhagen-Broschmann plates: 15 seconds
Matsubara colour plates: 10 seconds
These recommended presentation times can be changed manually in the Binoptometer® 4P software by selecting “settings” and then “system”.
