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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    In the fifth and last form, mixed astigmatism, the most rap- idly curved meridian is the myopic; the least rapidly curved, the hypermetropic. If you were all Ophthalmic Surgeons, it would be superflu- ous for me to add that regular astigmatism, which includes the five kinds just mentioned, is congenital in its origin; and its duration is commensurate with the lifetime of the individ- ual. While there are opinions to the contrary, it is the con- viction of the author of this paper that, so long as the astig- matic cornea remains free from pathological changes, the kind and quantity of the astigmatism remain invariable. That is to say, the radii of curvature of the two principal meridians bear at all times the same relationship to each other. What effect has astigmatism on the retinal image? Sup- pose the object looked at to be a line occupying a position at right angles to the meridian of best curvature. Its image will be more or less sharp, depending on the quantity of as- tigmatism, except at its two extremities, which will be blurred. If the line corresponds to the best meridian, the whole image is so marred that the line is not well seen. If the two principal meridians are respectively vertical and hor- izontal, the retinal image of a horizontal or vertical object is unaffected except in sharpness of outline as indicated above. In all cases of oblique astigmatism there is something more than a simple blurring of the image. In eyes free
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