The directions of the apparent vertical and horizontal meridians of the retina and their modification from physiological and pathological causes : with a description of the clinoscope / by George T. Stevens.

  • George Thomas Stevens
Date:
[1897]
Catalogue details

Licence: Public Domain Mark

Credit: The directions of the apparent vertical and horizontal meridians of the retina and their modification from physiological and pathological causes : with a description of the clinoscope / by George T. Stevens. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    of Listing, Helmholtz deduced his remarkable demonstration of the horopter in its various positions. Meissner also found a tilting of the apparent vertical me- ridians, but worked out a different theory of the horopter. Hering, however, found no convergence of the vertical meridians and of course arrived at a conclusion quite differ- ent from that of Helmholtz. A subject of great physiological interest then has been thrown into confusion by the variation of data from which learned and conscientious investigators have drawn their conclusions. It has become the custom of recent writers to mention the subject of the horopter as one having no physio- logical value, or even to speak of it with a measure of dis- dain. The illustrious Helmholtz has been accused of a waste of time on his own part, and a demand for a waste of energy on the part of his disciples in their attempts to fol- low his analytical reasoning and his abstruse mathematical formulae. We shall make no mistake if we regard this subject to which Helmholtz devoted so much time and research as one which, when rightly comprehended, is of weighty interest to the practical ophthalmologist, and that it is by no means a subject of scientific curiosity only. Leaning of the Vertical Meridians in Paralyses.—There is another field of research in respect to the position of these vertical and horizontal meridians which will perhaps appeal more directly, in the present state of our knowledge, to the practical ophthalmologist, and that is in regard to the degree and direction of their tilting in cases of paralysis or paresis of the motor muscles of the eye. At present, in the diag- nosis of paralysis of these muscles, it is customary to observe the fact of the tilting of images, but of the exact extent little or no notice is taken. Although there are means of arriving at a rough estimate of this leaning, I believe that in no text- book on ophthalmology is it recommended to employ even these rude methods. It may also be a subject of practical interest, indeed in certain cases it is such, to determine the extent of torsion which a patient may be able to induce and especially to de-
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