1st- and 2nd-order disparity stimuli elicit vertical vergence eye movements in alternating esotropia

Two different disparity detecting systems are described in humans: one uses luminance defined stimuli (1st-order) and the other non-luminance, e.g. contrast defined stimuli (2nd-order). These systems might have different susceptibility to discordant visual input to both eyes in early life. Subjects with strabismus show a wide variety of deficits of 1st- and/or 2nd-order stereo acuity, but the determining parameters for the development of deficits of the 1st- and 2nd-order disparity system is unclear yet. To better quantify the early processing of the different disparity signals, we used an objective method, the…