An international system of ophthalmic practice / edited by Walter L. Pyle.

  • Beard, Charles H., 1855-1916.
Date:
1913
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Licence: In copyright

Credit: An international system of ophthalmic practice / edited by Walter L. Pyle. 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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    IN ANEMIA AND ISCHEMIA calibre of the retinal vessels are lack of volume or force in the blood-stream, spasm of the muscle tunic (of arteries), thickening of the intima, and atrophy of all the tunics. In ordinary simple and secondary atrophy of the optic nerve and retina it is manifestly real, for even the outside measure- ments of the accompanying white streaks are less than the corresponding normal ones. The white lines in atrophy are relatively wider, however, than in simple contraction of a vessel, because of the connective-tissue degeneration of the walls. This is particularly true of those of secondary atrophy. Consequently more of the blood stripe is concealed. The latter also appears of lighter color, partly because of the thinning and partly because seen through and against a white film. Anemia.—Attenuation and pallor of the retinal vessels are not constant symptoms of general anemia. One no longer pretends to ascertain the degree of anemia by ophthal- moscopic examination. It is none the less certain that in more than half the cases of pronounced benign anemia and chlorosis there is diminution of both arteries and veins with lack of color in their blood. The relative difference in size between arteries and veins is not maintained but is accen- tuated, the latter being but slightly reduced, and sometimes even enlarged. Ischemia.—This refers to local and sudden depletion of the retinal vessels. It may or may not be accompanied by general symptoms. Its chief causes are collapse, less cardiac energy, occlusion of the retinal blood-vessels and vasomotor reflex influences; the last inducing spasm of the retinal arteries. Von Graefe and deWecker examined vic- tims of cholera in the stage of asphyxia and noted attenu- ation of the retinal arteries so extreme that they could be traced but a short distance from the papilla. The veins, too, weie greatly narrowed. Certain cases of bilateral ischemia sufflcient to cause complete blindness have been attributed to an enfeeblement of the heart's action to such a degree that the force of the blood-current in the retinal 18