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Hiding Heidi Contrast test (Good-Lite, Elgin, IL, USA). (A) The cards from highest (100%, top left) to lowest (1.25%, bottom right) contrast, where the % contrast can be seen at the bottom right hand corner of each card. (B) During testing, the Hiding Heidi Contrast card would be revealed under a white card and the examiner would look for shift of gaze or head turn toward the visual stimuli, here the card with 5% contrast is shown.
