Ophthalmovascular choke / by George M. Gould.

  • Gould, George Milbrey, 1848-1922.
Date:
1908
Catalogue details

Licence: In copyright

Credit: Ophthalmovascular choke / by George M. Gould. 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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    HOT] frabulbar arteries have no pulse-beat seems in itself proof of some vascular compression in the nerve, and an added one is the fact that sometimes the venous blood can escape only be- tween the posteriorly placed beats of the artery. Infrabulbar choice may possibly be a simple or secondary consequence of retrobulbar choke, through the added pressure in the arterial blood columns to force an entrance, and through the resultant venous turgidity and impeded outflow of the venous blood. But if there is a plainly added patho- genetic factor easily demonstrable by the ophthalmoscope, and, from the evolutionary history and from the physiology of the eye, most likely to occur, then we have a doubling of two pos- sible pathogenetic agencies which will easily become really denutritional and disease-producing. Such a cause is that found in the ten cases above reported,—crossing of the ves- sels over or under each other, with resultant impeding of the flow of the-blood-currents. The pecten, and the shading mechanisms of the retina must be considered to make clear how and why these infrabulbar chokings have arisen. I do not know that any one has sug- gested a function or raison d’etre for the pecten in birds. It could scarcely be a “ mistake of Nature,” or a mere curiosity for a true scientific man. The danger to the retina of man from direct exposure to the sun’s rays is of course well known. Even as little as he need to expose his eyes to these rays in the labors, games, or wars of life, Nature has found it necessary to supply the retina with more than a dozen distinct, in- genious, and differing mechanisms elsewhere described by me, for shading the retinas. But in animals by their habits neces- sarily exposing the retinas to the danger of direct sunlight, some of these mechanisms do not exist, and all would, in the birds, be insufficient to prevent retinal injuries from this source. Waving about freely and extensively in front of so large portions of the fun (buses of the eyes of birds the pecten admirably serves as an ever-moving and protecting curtain. The constant motion of the head and eyes keeps up the alter- nate shading and exposure of the retinas that is required. Anatomically it is a loose mass of blood-vessels. In the higher vertebrates and man it is not needed, and, as it were, becomes