Patent ID: 7773769

Claim:
An apparatus for characterising a subject's visual response, and comprising a data processor, a display, and an input device; wherein: the data processor is arranged to present evaluation images at different positions on the display such that they occur at different positions within the subject's field of view; each evaluation image comprises a contribution of at least two items selected from a list comprising: a base image, a test image comprising alternating regions of color or intensity, and a noise image; a plurality of the evaluation images are formed of a base image, a test image and a noise image so as to assess the limit of the subject's ability to identify the test image in the presence of noise as a function of position; and the data processor is responsive to the input device such that the subject can indicate whether the subject can see the test image in the evaluation image, and the data processor is further arranged to evaluate the subject's responses so as to give an indication of internal noise and one or more indications of visual efficiency and visual sensitivity as a function of position within the subject's field of view.