1. A method of providing a visual reaction map of at least part of the visual field of an eye of a subject, the method comprising: (a) presenting to said visual field a plurality of segments each of the segments comprising an individually activated image; (b) changing each of said individually activated images in each of said segments according to a binary sequence each of said images being changed in a different way from all other of said images whereby the changing of one of said images does not substantially correlate with the changing of any of the other of said images; (c) detecting measurement signals in said subject while said visual field is presented with said changing; (d) correlating said measurement signals with each of the binary sequences used to activate each of said individual segments; and (e) providing said visual reaction map from said correlating.