OBJECTIVE To investigate and classify the ophthalmic artery (OA) flow patterns in patients with occlusive carotid artery disease (OCAD). METHODS Forty-three patients (52 eyes) with documented OCAD of > or =70% underwent orbital color Doppler imaging. The eyes were first divided into four groups by peak systolic velocity in OA (PSV(OA)): group A, PSV(OA) < or = 0; group B, 0 < PSV(OA) < or = 10; group C, 10 < PSV(OA) < or = 40; and group D, PSV(OA) > 40 cm/s, then further classified by the shape of the OA flow wave. The groups were then compared with respect to the collateral pathway (Co-Path), severity of the OCAD, and systemic diseases. RESULTS Eyes with unidirectional reverse flow (group A(1)) had a Co-Path from the ipsilateral external carotid artery and 70%-100% OCAD. Eyes with bidirectional reverse flow (group A(2)) had no Co-Path, 75% OCAD, and impending ischemic heart disease (IHD). Group B eyes had dome-shaped OA flow waves with no Co-Path and 99%-88% OCAD. Group C(1) eyes, with normal flow waves, had a Co-Path from the contralateral internal carotid artery and 100% OCAD. Group C(2) eyes, with triangular-shaped flow waves, had no Co-Path, 93%-70% OCAD, and IHD. Group D eyes had normal high flow waves with no Co-Path, 75% OCAD, and hypertension. CONCLUSIONS The OA flow patterns were variously affected by collateral pathway, severity of OCAD, and systemic diseases.