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.

  • Stevens, George T. (George Thomas), 1832-1921.
Date:
[1897]
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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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    THE DIRECTIONS OF THE APPARENT VERTI- CAL AND HORIZONTAL MERIDIANS OF THE RETINA AND THEIR MODIFICATION FROM PHYSIOLOGICAL AND PATHOLOGI- CAL CAUSES, WITH A DESCRIPTION OF THE CLINOSCOPE. By GEORGE T. STEVENS, M.D., Ph.D., New York. Comparison of Data Regarding Retinal Meridians.—If the point of regard of the two eyes is fixed in the median and in the horizontal plane and at infinite distance, while the head of the observer is in the primary position, it might be assumed that the vertical meridian of each retina would coincide with a plane perpendicular to the plane of regard and that the horizontal meridian would coincide with the plane of regard. Yet in respect to a proposition so apparently simple and involving questions of great importance, practical as well as theoretical, the views of the ablest investigators have been at variance; for while Helmholtz concedes that the horizontal retinal meridians so nearly coincide with the plane of regard that they may be considered as practically identical with it, he characterizes the vertical meridians as apparent vertical meridians, and he reasons from his own experiments, and those of Volkmann, that these apparently vertical meridians as a matter of fact, in normal eyes, converge downward to the extent of ij° each, making thus an angle between the vertical meridians of the two eyes of 2\° with the lower ex- tremities of the meridians approaching each other. Basing his calculations on this proposition and on the law Reprinted from the Archives of Ophthalmology, Vol. xxvi., No. 2, 1897. {Four figures in the text.)