Ocular pneumoplethysmography as diagnostic aid in carotid stenosis
The ocular pneumoplethysmograph as developed by Gee was evaluated for its accuracy in demonstrating the presence of stenosis in the internal carotid artery. An initial study on 30 Chacma baboons showed that it was very reliable in demonstrating narrowing of 70% or greater of the internal carotid artery. In its clinical application 3 studies were done: The first group of 100 patients were all asymptomatic regarding cerebral ischemia. 23 had a murmur over the carotid artery and of these 57% had an ipsilaterally positive OPG-Gee test. In the 77 without a carotid murmur, 32% had a positive OPG-Gee test. Of 25 patients who had a history of cerebral apoplexy, 6% had a positive OPG-Gee test on the side of the cerebral lesion. 50 patients were referred for an OPG-Gee test because of suspected cerebral ischemic episodes. Half of these had a positive OPG-Gee test, but if a carotid murmur was present, 82% had a positive OPG-Gee test. In 34 cases with a positive OPG-Gee test a carotid arteriogram was obtained. In all but one case this confirmed the presence of a stenosis in the common or internal carotid artery, giving an incidence of 3% false positive findings in this series.