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.

    27/288 page 15
    There are but two ways of accounting for the absence of this peculiar kind of double vision in such forms of astig- n^atism as that represented in Figures 2 and 4. Sectional ciUary contraction would account for it. If it were possible for the ciliary muscle thus to act, one can readily under- stand how the curvature of the lens could be so changed as to result in lenticular astigmatism equal, but at right an- gles, to the corneal astigmatism. If such ciliary action were to take place in the right eye of either Figure 2 or 4, the ret- inal image would not only be made as sharp as if in an em- metropic eye, but it would also be made to lose its obHquity, and thus double vision would be prevented. x\s beautifully as this sectional ciliary action would account for the absence of double vision in cases of obhque astigmatism, it is cer- tainly a false theory, since, when all cihary power has been suspended by atropine or age, the eyes are still able to do something by means of which the double vision represented by Figure 8 is prevented. If sectional cihary contraction does not occur, then the two eyes represented by Figure 2 or 4 have no inherent power by means of which the relative direction of the two retinal images can be changed; hence there must be double vision, unless the obhque image in the right eye and the hor- izontal image in the left can be made to occupy correspond- ing parts of the two retinae. This can be effected alone by the harmonious symmetrical action of the oblique muscles.
    digitised image 1
    digitised image 2
    digitised image 3