The harmonious non-symmetrical action of the oblique muscles explains 'binocular astigmatism' / by G.C. Savage.

  • G. C. Savage
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: The harmonious non-symmetrical action of the oblique muscles explains 'binocular astigmatism' / by 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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    of its vertical corneal meridian point up and out. This would make the naturally vertical meridians of the corneae divergent at upper corneal margin and convergent below. Marked dou- ble vision would result, the two images of a vertical object, leaning toward each other at their tops. If we could suppose that double vision would not result, the image of the object looked at through the glasses as adjusted in the monocular examinations, if a rectangle, would be narrow at the top and wide at the bottom, a phenomenon not referred to by Dr. Cul- bertson. It is clear that the explanation for “binocular astigmatism,” as given by Dr. Culbertson, is not correct. 2. Toward the close of his paper (p. 123) Dr. C. says his explanation may not be true, and adds: “Accommodation may have a direct influence in the result, by changing the fo- cus of individual sectors of the crystalline lens,” referring to Martin’s theory of the sectional contraction of the ciliary muscle. The fact that “binocular astigmatism” exists to some extent in some cases when all ciliary power has been suspended by atropia or homatropia, is strong proof that sectional ciliary ac- tion does not cause it. I am not convinced that sectional cili- ary action ever occurs, but I am sure that it never causes “binocular astigmatism.” Let us study, in reference to Martin’s theory, a case of sim- ple hypermetropic astignatism, with the emmetropic meridian in right eye at 750, and that of left eye at 105°. Under suspen- sion of accommodation we find the glasses needed to be-{-3 cyl. ax., for right eye at 750, and for left at 105°. If Martin’s theory be true, such eyes, when uninfluenced by medicine, have the power of partly correcting their faulty, without changing the refraction of their correct, meridians. To do this that part of the ciliary muscle behind the meridian at 75° in right eye, must not act while every other part must be thrown into ac- tion, the maximum of power being exerted by that part behind the meridian at 165°. The same may be said of the left eye substituting 105° for 750 and 150 for
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