There is no question that false torsion or its synonym, torsion, exists. Helmholtz1 has pages of illustrations and formulas proving this, but I have not been able to discover a paragraph in which he tells why it occurs. Presumably Helmholtz thought anyone would know why. On the contrary, subsequent writers have presented so many different points of view on the subject that the reason for false torsion must not be clear. If this point can be elucidated, the way may be opened to some new avenues of investigation into the physiology of ocular movements.
It should be useful, for example, to have a simple, clear explanation of why Donders2 found that when the eyes turn obliquely up to the left the corneal meridians tilt clockwise when compared with a vertical reference plane, but Helmholtz found that for the same oblique rotation the corneal meridians and retinal horizon tilt