In detail, the identification of the theoretical/geometrical horopter with the Vieth-Müller circle is only an approximation. It was pointed out in Gulick and Lawson (1976) that Müller's anatomical approximation that the nodal point and eye rotation center are coincident should be refined. Unfortunately, their attempt to correct this assumption was flawed, as demonstrated in Turski (2016). This analysis shows that, for a given fixation point, one has a slightly different horopter circle for each different choice of the nodal point’s location. Moreover, if one changes the fixation point along a given Vieth-Müller circle such that the vergence value remains constant, one obtains an infinite family of such horopters, to the extent that the nodal point deviates from the eye’s rotation center. These statements follow from the Central Angle Theorem and the fact that three non-collinear points give a unique circle. It can also be shown that, for fixations along a given Vieth-Müller circle, all the corresponding horopter circles intersect at the point of symmetric convergence. This result implies that each member of the infinite family of horopters is also composed of a circle in the fixation plane and a perpendicular straight line passing through the point of symmetric convergence (located on the circle) so long as the eyes are in primary or secondary position.