We performed 4D Flow MRI assessment of the ophthalmic artery (OphA) flow in patients with internal carotid artery stenosis (ICS). Twenty-one consecutive patients with unilateral ICS were recruited. 4D Flow MRI and acetazolamide-stress brain perfusion SPECT were performed. The flow direction on the affected-side OphA was categorized into native flow and non-native flow based on 4D Flow MRI. In the affected-side MCA territory, the ratio of rest cerebral blood flow to normal control (RCBFMCA) and cerebral vascular reserve (CVRMCA) were calculated from SPECT dataset. Eleven patients had native OphA flow and the remaining 10 had non-native OphA flow. RCBFMCA and CVRMCA were significantly lower in non-native flow group (84.9±18.9% vs. 69.8±7.3%, p<0.05; 36.4±20.6% vs. 17.0±15.0%, p<0.05). Four patients in the non-native flow group and none in the native flow group were confirmed as high-risk (Sensitivity/Specificity, 1.00/0.65). The 6 min-standard 4D Flow MRI assessment of OphA in patients with ICS can predict intracranial hemodynamic impairment.