A method of providing a visual reaction map of at least part of the visual field of an eye of a subject comprises: (a) presenting to the visual field a plurality of segments with each of the segments comprising an individually activated image; (b) changing each of the individually activated images in each of the segments according to a binary sequence with each of the images being controlled with a different sequence taken from a family of sequences whereby each one of the sequences does not substantially correlate with the changing of any of the other sequences in the family; (c) detecting measurement signals in the subject while the visual field is presented with the changing; (d) correlating the measurement signals with each of the binary sequences used to activate each of the individual segments and (e) providing the visual reaction map from the correlating. The binary sequences are selected from Gold, Kasami, Bent- function and a combined Kasami and Bent-function family.
Electroretinogram (ERG) using image segments which stimulate output signals with very little cross-correlation