Cardiff Acuity Test
The test combines the principles of preferential looking and vanishing optotypes. It is based on the premise that a child, when presented with two different patterns, will fixate on the picture rather than on a plain stimulus. The test uses pictures that will interest a child (house, car, duck etc.) positioned either at the top or at the bottom of an otherwise grey card. There are eleven visual acuity levels, with three cards at each level.