Addendum to the paper More about True and False Torsion by Manuel Marquez

(Ophthalmologica, Vol. 129, No. 2, p. 137) Roelofs’ conception of false torsion and true torsion does not differ from mine. His statement that it differs is, I think, due to a misunderstanding. Torsion of the eye, defined in the simplest terms, is a condition when the normal vertical meridian of the eye (cornea or retina) is tilted or inclined to one side or the other (producing intorsion or extorsion) with reference to a true vertical plane. Of course an inclination of the normal vertical meridian is accompanied by an inclination of the normal horizontal meridian and all other meridians. We can thus define torsion also with reference to the inclination of the normal horizontal meridian of the eye. Roelofs’ suggestion to visualize a vertical plane passing through the visual axis (line of gaze) and thus outlining a true vertical corneal and retinal meridian with which to compare the inclined normal vertical meridian is very good. This idea is implicitly contained in the definition which I used in the original article, speaking of “the normal vertical meridians being inclined from the true vertical”. I don’t believe it will help any to discuss Roelofs’ criticism. The only question about which there is some doubt and a difference of opinion is this. In false torsion produced when the eye rotating on an axis in Listing’s plane looks in an oblique direction say up and out do the corneal and retinal meridians incline in the same direction or in opposite directions one to the other? Experiments with balls as Marquez describes in this article also similar experiments which I have made seemed to show that in false torsion the corneal and retinal meridians do rotate in opposite directions. However some new experiments more recently performed seem to show the contrary namely that the corneal and retinal meridians rotate in the same direction but possibly not to the same extent. I have not yet concluded these experiments. But I hope they will help to unravel this puzzle in pseudotorsion. Marquez however is still firmly convinced that the corneal and retinal meridians rotate in opposite directions as shown in the appended article.