Treatise on the diseases of the eye : including the anatomy of the organ / by Carl Stellwag von Carion ; tr. from the 3rd German ed. and ed. by Charles E. Hackley and D.B. St. John Roosa ; with an appendix by the editors.
- Karl Stellwag von Carion
- Date:
- 1870
Licence: Public Domain Mark
Credit: Treatise on the diseases of the eye : including the anatomy of the organ / by Carl Stellwag von Carion ; tr. from the 3rd German ed. and ed. by Charles E. Hackley and D.B. St. John Roosa ; with an appendix by the editors. Source: Wellcome Collection.
Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.
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![movements of the head at the same time; and the statements of the patients as to the situation of the double images is very untrustworthy. The neglect of these circumstances does not allow us to accept the rules heretofore given, in accordance with which the paralysis of individual muscles was diagnosticated from the relative position of the double images {Graefe. Schuft, [Waldau,] Alf. Graefe), except with the greatest care, and the more so, since we obtain very incorrect ideas as to the uormal inclination of the meridians in the various directions iu which the view may be turned. a. If a lateral rectus alone be paralyzed, the visual axis of the eye to which it belongs, with a primary position of the other, deviates horizontally from the object of fixation, in the course of the antagonist. If the gaze in the course of the para- lyzed muscle be turned horizon'ally to one side, the affected globe follows the healthy one, for a cert an distance, but always remains behind the latter, and if there be a complete paralysis of the muscle, does not pass beyond the median posi- tion. The rota: ion is, then, on both sides around a vertical axis, and only a little less on the affected side. The two retinal images are therefore of the same hight, but thrown upon different horizontal meridians, and appear about parallel to each other, and equally high, but crossed or homonymous, according as the internal or external rectus may be pnralyzed. If now, while the ideal visual plane maintains the horizontal position, the head be moved greatly forward or backward, so that the former appears relatively raised or sunken, the visual axis will again remain behind, if the gaze be turned laterally in the course of the paralyzed muscle. Consequently, the vertical meridians of the two retinas will not be parallel, since this is possible only with parallel visual axes, but in accordance with Listing's law, the one retina, in comparison to the other, will be distorted. In unison with this, the double images of a line vertical to a horizontal ideal visual plane will seem inclined to each other, always providing that all the fibers of the affected muscle are equally paralyzed, and that its resulting direction of action has undergone no great change. If, for example, the right external rectus is paralyzed, and if the gaze be directed toward the right, with the head strongly inclined forward, and with a horizontal ideal visual plane, both visual axes will be at about the same bight, but the right will incline a little inward ; conse- quently the horizontal meridian of the right retina will be inclined with its upper extremity a little less to the left than that of the left retina, which is turned more to the right. The homony- mous images will therefore converge upward to a line vertical to the ideal visual plane. On the other hand, they will diverge above if the gaze is turned toward the right, while the head is strongly inclined backward, and there is a horizontal ideal visual plane. According to experi- ence, the deviation appears m ich less frequently, on lifting np the visual plane, than in looking down. The reason of this is, that the latter movement is only made naturally, in looking at near objects, and this is accompanied by great convergence of the visual axes (Seliuft, Waldau), and powerful tension of the muscle of accommodation is made. If the right internal rectus be alone paralyzed, crossed double images must appear, when the head is strongly inclined forward, and the gaze is directed to the left, and the false image belong- ing to the affected eye with that of the other side will converge upward, but diverge when the head is inclined very much backward, and the gaze is directed horizontally to the left. b. If a superior or inferior rectus be alone paralyzed, the visual axis of the affected eye, with the primary position of the other, deviates upward or downward, according as it is the inferior or superior rectus which is affected, and with this there is said to be a slight deviation outward. (Graefe.) Moreover, the retina of the affected eye is also distorted a little toward that of the healthy one. It has under-](https://iiif.wellcomecollection.org/image/b2107902x_0751.jp2/full/800%2C/0/default.jpg)
