1. Apparatus for testing the visual response of a patient, the apparatus comprising image generation means, image presentation means, and detection means, the image generation means and image presentation means being arranged, in use, to generate and present an image before an eye of the patient at variable predetermined intensity levels, and the detection means being arranged, in use, to detect a stimulus response to the presented image occurring in the brain of the patient, wherein the image generation means is arranged, in use, to generate images of progressively increasing intensity or brightness on the image presentation means.