Visual acuity in a human subject is tested by sequentially presenting to him (for short time instants) a series of visual images. Each image in one particular example is circular and one quadrant of each presented circle is formed with a chequer pattern of areas of contrasting luminance or color. The position of the chequer pattern in each image and/or the spatial frequency of the pattern in each image is different from that for the other images, and for each presentation, the subject is asked for his response.
Method and apparatus for determining visual acuity in a human subject