Ocular rotations / G.C. Savage.

  • G. C. Savage
Date:
1907
Catalogue details

Licence: In copyright

Credit: Ocular rotations / G.C. Savage. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    vertical plane with H and G' mnst be in a vertical plane with G. G' and H' are, therefore, in the vertical retinal meridians of their respective eyes. In changing the point of view from C to C' the extended plane of the circle C-B-D must be rotated on the chord B-D until it occupies the position of the secondary isogonal circle C'-D-B. In doing this the visual axes H-C and G-C are made to take the places of the indirect visual lines H'-C' and G'-C'. In this rotation the visual axes and the two horizontal retinal meridians have remained in the plane of the primary isogonal circle; nor in this rotation have either the visual axes or horizontal retinal merid- ians changed their positions in this plane. Since C' is directly above C, the visual axis H-C has moved to C' in the extended plane of the vertical meridian of the left eye, and the visual axis G-C has moved to C' in the extended plane of the vertical meridian of the right eye. The visual axis moves from one point of view to another point of view in a plane common to these two points of view and the center of rotation. C' i& just as high above C, in degrees of arc, as H' is below H, for the angle C-B-C' is equal to the angle H-B-H', since they are opposite angles, and each is measured by that arc of the vertical meridian between H and H'. By the same reasoning we find that the angle formed by the planes of the primary retinal curve N-H-S and the secondary retinal curve N-H'-S along the line H-B-S is the same as the angle formed by the planes of the primary isogonal circle C-B-D and the secondary isogonal circle C'-B-D, along the chord B-D, for they are opposite. If the point of view is to be changed from C on the primary isogonal circle on E on the secondary isogonal circle, the plane of the primary circle would be rotated upward on its chord B-D until it reaches E, replacing the plane of the secondary circle C'-B-D, just as it did when the second point of view was C', and in the new posi- tion would still contain the two visual axes and the two horizontal retinal meridians. But from the beginning to the end of this rising of the primary plane the visual axes and the horizontal retinal merid- ians would be shifting in it toward the right, and at the moment the plane reaches the point E the visual axes would be converged on it. The visual axis H-C in going from C to E has not only shifted its position in the primary isogonal plane, but has moved in a plane common to C, the primary point of view, F, the secondary point of
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