Carotid compression tonography: a new test for carotid insufficiency.

Abstract

Wessely (1908) showed that occlusion of one common carotid artery caused an ipsilateral fall of intraocular pressure. Recently ocular tonography during common carotid compression has been used to assess blood flow to the brain in cases suspected of carotid insufficiency (Barrios and Solis, 1966;McLean and Galin, 1966). The purpose of this paper is to demonstrate that carotid compression tonography is a reliable screening test for carotid insufficiency. Material and MethodForty-two patients were referred for exclusion, confirmation, or diagnosis of carotid insufficiency. Each patient lay flat with neck exposed and eyes fixed on a dim light above his head. A drop of local anaesthetic was instilled into each conjunctival sac. The intraocular pressure was measured graphically with a self-recording electronic tonometer placed on one eye. The ipsilateral common carotid artery was compressed with a thumb for one to two seconds, low in the neck to minimize the risk of stimulating the carotid sinus. When the recording of intraocular pressure had returned to normal the contralateral common carotid was compressed. The same procedure was repeated with the tonometer placed on the other eye. Interpretation of ResponseNormal Response (Fig. 1 (Fig. 2); the absence of a crossover fall suggests supply from the basilar artery. A reduced response to ipsilateral compression, which may also be delayed in onset and slow to recover, suggests a degree of carotid insufficiency. A crossover fall has the same significance as before except that its absence may be due to the presence of ipsilateral external carotid collaterals.In unilateral disease the responses from the other eye are normal. If these are abnormal, bilateral disease is indicated, and the nature of the crossover responses provides evidence of the type of collateral circulation (Fig. 3). ResultsOut of 42 recordings 35 were judged satisfactory and seven poor, the latter because of an irregular resting tracing or blepharospasm or movement during carotid pressure; these were discarded. The clinical presentation and results of carotid compression tonography in the 35 former patients are summarized in Tables I and II

Evaluation of ocular pulse amplitude in patients with carotid artery stenosis using the Pascal dynamic contour tonometer

“…The OPA levels in Groups 1 and 2 were found to be similar. The effect of carotid stenosis on OPA readings has been previously examined in several studies using different methods (mostly tonography, ophthalmodynamometry or pneumatic applanation tonometry); in all of these studies, OPA was found to be lower in patients with CAS, and the researchers suggested OPA as a potential screening test for CAS . However, the methods they used for OPA measurements were mostly complex and are not readily available for clinical use.…”