Carotid - Ophthalmic Anastomoses *

ANATOMICAL studies in man on the degree of anastomosis existing between the external carotid artery and the ophthalmic arteries are a necessary condition of the rational surgical treatment of carotid-cavernous fistulae, as this treatment may carry with it a threat to vision in the eye on the operated side if the anastomosis is inadequate. What must be proved is the negative proposition that inadequate anastomosis is rare. Previous anatomical studies do not enable the risk to be accurately assessed, as the number of subjects studied has been too small. Thus the evidence based on perfusion experiments described in the literature does not permit one to 5tate that adequate anastomosis is to be expected in more than 62 per cent. of the population (Elschnig, 1893; Garwood, 1936; Walsh and King, 1942). The present study was planned with two objects in view. First, it was necessary to choose methods of testing that adequate anastomosis existed, though the use of autopsy material limited the choice to perfusion with water, air, and blood. The use of dyes or neoprene casts was ruled out, and perfusions with blood had to be brief. However, it was possible to test the anastomosis satisfactorily, by demonstrating that a copious backperfusion occurred within specified conditions of time and perfusion pressure. Secondly, it was necessary to demonstrate that this copious anastomosis existed in all or nearly all of as large a series of perfusions as possible. Only in this way can the frequency of anastomosis be accurately assessed. From an analysis of the results obtained (Tables I, II, and III) it is concluded that the occlusion of the ophthalmic artery central to the point of origin of its central retinal branch is unlikely to deprive the retina of an adequate anastomotic blood supply. A review of the literature concerning the effects of operations involving ligation of the internal carotid artery points to a similar conclusion. It would not seem that the contralateral anastomosis is always as extensive.