Effect of an internal carotid stenosis on orbital blood velocity

Purpose. To examine how an internal carotid artery (ICA) stenosis influence s the orbital blood velocity and to determine which velocity parameters are most useful. Material and Methods. The study group comprised 94 randomly selected patien ts examined with orbital US; most of the patients had a carotid artery sten osis. There were 58 men and 36 women, ranging in age from 22 to 88 years wi th a mean age of 63.1 years. The ICA stenosis grade was determined with car otid US. Peak systolic (Vp) and end-diastolic blood velocities, systolic ac celeration, mean velocity, pulsatile index (PI) and resistance index (RI) w ere measured within the central retinal artery (CRA) and the ophthalmic art ery (OA), and peak velocity was measured within the central retinal vein (C RV). The area under the ROC curve was used to compare the outcome of diagno stic tests. Results. Only a severe (greater than or equal to 80%) ICA stenosis decrease d orbital blood velocity significantly, while milder stenoses did not cause significant flow decrease or side differences. According to ROC curve anal ysis, the threshold values giving the highest accuracy in detecting a great er than or equal to 80% ICA stenosis were Vp less than or equal to 0.08 cm/ s for the CRA and Vp less than or equal to 0.14 cm/s for the OA. The sensit ivities for detecting a greater than or equal to 80% ICA stenosis were 45% for Vp CRA and 60% for Vp OA. Systolic acceleration also decreased in sever e stenoses, but RI, PI and velocity in the CRV did not correlate with ICA p athology Reversal of OA flow was seen in 92% of ICA occlusion and in 47% of severe ICA stenosis. Conclusion. Orbital Doppler combined with carotid Doppler can be helpful in the diagnosis of the ocular ischaemic syndrome and in the evaluation of wh ether the symptoms are related to occlusion of the ophthalmic or central re tinal vessels or are a consequence of carotid artery stenosis.