Acquired colour vision defect tested with different sorting tests

Acquired patchy defects of central visual field cause varying losses of colour vision in different parts of the central visual field and result in different kinds of confusions, when either the saturation (the amount of colour mixed with white) or the size of the test is varied.

A person who makes several major errors that give rise to lines crossing the colour circle on Lanthony's Desaturated Test (weak pastels colours mixed with white, Figure 7A) may perform better on the regular Panel D-15 or Panel 16 small stimulus testing (Figure 7B) and still better on the Panel 16 test when large stimuli are used (Figure 7C). This may be because testing with a larger stimulus covers more area of a normally functioning retina and thus the person can more easily compare the caps with larger surfaces.