ASSESSMENT OF THE OPHTHALMIC ARTERY AS A COLLATERAL TO THE CEREBRAL-CIRCULATION - A COMPARISON OF TRANSORBITAL DOPPLER ULTRASONOGRAPHY AND REGIONAL CEREBRAL BLOOD-FLOW MEASUREMENTS

The role of the ophthalmic artery (OA) as a collateral to the cerebral circulation in carotid occlusive disease is somewhat controversial. T he aim of this study was to assess the importance of this collateral b y comparing the results of transorbital Doppler ultrasonography and re gional cerebral blood flow measurements using SPECT and Xenon-133 inha lation in 41 patients with unilateral high-grade internal carotid arte ry occlusive disease. Both measurements were performed under basal con ditions and after the intravenous administration of 1 g acetazolamide to test cerebral vasoreactivity. Based on the direction of OA flow, th e patients could be divided into three groups. In Group 1 (n = 16) wit h anterograde OA how before and after acetazolamide, baseline rCBF val ues did not differ significantly between the two sides, or from those of the controls. The side-to-side assymmetry of the response to acetaz olamide was also normal. In Group 2 (n = 11) where the OA flow was ant erograde or ''0 flow'' before, but became retrograde after acetazolami de, rCBF was significantly reduced on the symptomatic compared to the non-symptomatic side under basal conditions. However, the increase in rCBF after acetazolamide was within normal limits. In Group 3 (n = 14) the OA flow was reversed both under basal conditions and after the va sodilatory stimulus. Baseline rCBF was significantly lower (p < 0.05) on the symptomatic side compared to the non-symptomatic, and the asymm etry became even greater (p < 0.001) after acetazolamide. Our findings demonstrate that the OA may be an important collateral pathway in pat ients with ICA occlusive disease, and contribute to the cerebral perfu sion reserve in the case of compromized blood supply.