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CHESTER HYMAN; The Concept of End Arteries and Diversion of Blood Flow. Invest. Ophthalmol. Vis. Sci. 1965;4(6):1000-1003.
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Examination of the circulation in peripheral tissues has established the validity of certain theoretical hemodynamic concepts. The redistribution of blood flow between parallel vascular beds during unequal changes in their resistances seems to obey the general predictions of simple diversion. Such shifts of blood between vascular systems are exaggerated when the local perfusion pressure is diminished by abnormal upstream resistance. Diversion, as well as the deleterious effects of arterial occlusion, can be minimized if an adequate collateral circulation is established soon enough to prevent damage to the ischemic tissue. For tissues supplied by a true end artery, such collateral supply is ruled out by definition. Within the orbit the retinal artery is in fact an end artery while the ophthalmic artery may receive certain small collaterals. Redistribution of blood between the retina and the other orbital tissues is at least theoretically possible, and evidence for such a diversion should be sought in cases with clearly established partial occlusion of the ophthalmic artery. Since the retinal artery supplies only a single tissue, the diversions are limited to those betweeen the various portions of the retina, or between a nutritive or shunt circulation. Evidence for the latter type of diversion has already been presented. We suggest that it might be of value to check these theoretical projections by direct experimentation insofar as possible; findings of such studies should assist us in describing the dynamics of intraorbital blood flows.
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