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. Author manuscript; available in PMC: 2013 Oct 21.
Published in final edited form as: J Vis. 2011 Mar 29;11(3):10.1167/11.3.20 20. doi: 10.1167/11.3.20

Figure 1.

Figure 1

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.