New truths in ophthalmology / as developed by G. C. Savage.

  • G. C. Savage
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: New truths in ophthalmology / as developed by G. C. Savage. Source: Wellcome Collection.

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    that of the left are parallel. Point 5 in the rectangle is the point of fixation. The Hne 5-5 from the macula of the right eye is the visual axis of that eye, and likewise the line 5-5 is the visual axis of the left eye. These intersect at point 5 of the rectangle. According to the well-known law of refraction by curved surfaces, such as are now under consideration (non-astig- matic eyes), the rectangular object will throw a rectangular image on each retina, the size of which will bear a definite proportion to the size of the object. The nodal point of the right eye is x, through which all lines of direction from this eye must pass. The lower inner comer of the image is thus connected with the upper right-hand corner of the object by the line i-i. In the same way the upper inner corner of the image is connected with the lower right-hand corner of the object by the visual hne 2-2 ; and so on for the other corners of image and object. In like manner the corners of the rectangu- lar image in the left eye maybe connected with corresponding corners of the object by lines passing through the nodal point {x) of that eye. If the left eye should be excluded, the right eye would see the rectangle 1-2-3-4; S^^ should be screened, the left would see the same rectangular figure. Both eyes together, in obedience to both the law of corresponding retinal points and the law of projection, would see the one common rectangle 1-2-3-4. 'The superior and in- ferior recti in these eyes have kept the visual axes in the
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