From: The vertical horopter is not adaptable, but it may be adaptive Journal of Vision. 2011;11(3):20. doi:10.1167/11.3.20 Figure Legend: Geometric and empirical vertical horopters. Green and red spheres represent the left and right eyes, respectively. (a) The anatomical vertical meridians of the eyes are geometric corresponding points. When these points are projected into the world, they intersect at a vertical line in the head's mid‐sagittal plane (here through fixation): this is the geometric vertical horopter. (b) The empirical vertical horopter has crossed disparity below fixation and uncrossed disparity above fixation, causing a top-back pitch. Date of download: 12/23/2017 The Association for Research in Vision and Ophthalmology Copyright © 2017. All rights reserved.