The purpose of this investigation was to determine the influence of noncongruent stimuli on tonic accommodation and tonic vergence. Eight visually normal subjects were tested in a within-subjects design. Tonic states were measured using a haploscope-optometer immediately before and after viewing a reduced Snellen chart binocularly with suppression control in a synoptophore for 8 min. One stimulus was set at either 4 D or 4 MA, with the other set at either the maximally high (e.g., >4 D or 4 MA) or low setting (e.g.,