On retinal embolism : with two cases in which a normal standard of central visual acuity was retained / by C. O. Hawthorne.

  • Hawthorne, C. O. (Charles Oliver), 1858-1949.
Date:
[1907]
Catalogue details

Licence: In copyright

Credit: On retinal embolism : with two cases in which a normal standard of central visual acuity was retained / by C. O. Hawthorne. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    has perfect central or direct vision, but the field is restricted to a very limited area surrounding and including the fixation point. Manifestly, therefore, though the blood supply has been cut off from the greater part of the retina, it has remained effective to the macular region. It is perhaps not very un- common to find, in cases of retinal embolism, that a small part of the field is retained, this being due to a supply of blood reaching, in one way or another, the corresponding part of the retina. The source of this supply may be either a branch from one of the ciliary arteries (cilio-retinal artery), or a branch which takes origin from the central artery in its course in the trunk of the optic nerve. As the obstruction, whether embolus or thrombus, usually blocks the main artery at the level of the optic papilla, the circulation in a branch, such as the one just described, is not affected, and, consequently, when such a vessel exists, the blood supply, in spite of the block in the central artery, may be continued to a limited portion of the retina. Another possible explanation of the persistence of some part of the field of vision in cases of retinal embolism may be, as suggested by Coats, the establishment of capillary anastomoses between the ciliary and central visual systems. In Figs. 3 and 4 are shown two perimeter tracings from cases of retinal embolism, and each exhibits a small eccentric visual field, the existence of which is to be explained in one or other of the fashions just described. Neither in these nor in other similar instances, as a rule, does the retained portion of the retina include the macular region, and there is, therefore, loss of central vision. In each of the two cases here related, however, there was retention of central vision, and the explanation was evident on ophthalmo- scopic examination. As is seen in Fig. i (and the two cases presented a practically identical picture), the blood supply of the retina is here not wholly dependent on the central artery. Towards the outer part of the disc is another artery, which is at once recognised as a cilio-retinal vessel, a branch, that is, not of the central artery of the retina, but of the ciliary system. And, manifestly, while the branches of the central artery are greatly reduced in cahbre, the blood stream within them having been brought to a standstill and the distending force of the blood pressure being therefore absent, the cilio- retinal vessel is of relatively large calibre, and is in the enjoy-