Non-invasive diagnosis of mild to severe stenosis of the internal carotid artery.

A prospective masked study of the Langham Ocular Pressure Pulse Amplitude Procedure was made on 20 patients with arteriographically-confirmed completely patent carotid arteries (Group 1) and on 20 patients with either unilateral or bilateral stenoses of the internal carotid arteries (Group 2). The results are compared to similar studies previously reported on 20 patients with radiographically confirmed unilateral or bilateral occlusions of the internal carotid arteries (Group 3). The intraocular pressures, the pulse/intraocular pressure relations, and the ophthalmic arterial pressures were equal in pairs of eyes of Group 1 patients, and similar to those found in normal healthy subjects. The mean ophthalmic/brachial arterial pressure ratio in Group 1 patients was significantly higher than in normal subjects. In the Group 2 patients, the intraocular pressures were normal and all the measured parameters were similar in pairs of eyes, whereas, the ophthalmic/brachial arterial pressure ratios were significantly less than in the eyes of the Group 1 patients. The degree of stenoses of the internal carotid arteries (0 to 100%) as evaluated from arteriography varied inversely with the ophthalmic/brachial arterial pressure ratios (correlation coefficient 0.85). The coefficients of the sensitivity, the specificity, and the accuracy of the ophthalmic/brachial arterial pressure ratios in identifying the presence of stenotic lesions of the internal carotid artery defined by arteriography in the 120 eyes of the three groups were 89, 80, and 86% respectively. The ability of the Procedure to identify hemodynamic lesions of less than 50% is in keeping with published results of theoretical and experimental studies of the pressure gradient across stenoses in arteries with high rates of blood flow.