Vergence instabilities and the longitudinal horopter

The method of averaging was applied to the results of repeated measures of the longitudinal horopter for four subjects classified as binocularly normal and one anisometropic amblyope. The results produced a refined horopter locus and suggested that the so-called Vieth-Mueller circle is an adequate describer of the empirical longitudinal horopter, except in those cases involving uncorrected aniseikonia.