The geometric horopter.
Two aspects of the geometric horopter, which here is based on the criterion of equality of angle, are clarified. The first is that in the fixation plane (containing the nodal points and the fixation point) the locus of points lying on the horopter is the larger arc of a circle, and not a full circle as has been previously accepted. The second is that elsewhere, the locus of these points is a straight line perpendicular to this plane and midway between the eyes. These rules hold for both symmetric and asymmetric convergence, and for fixation elevated or depressed from the horizontal.
Loughborough Design School, Loughborough University, Leicestershire LE113TU, England, United Kingdom. p.a.howarth@lboro.ac.uk
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Howarth
D005133:Eye Movements; D005403:Fixation, Ocular; D006801:Humans; D008433:Mathematics; D012160:Retina / Q000502:physiology*