Background and Purpose Cerebral autosomal dominant arteriopathy with subcorti cal infarcts and leukoencephalopathy (CADASIL) is a progressive systemic nonathe rosclerotic angiopathy which causes ischemic strokes and vascular subcortical de mentia. A cross sec tional study was performed to examine the retinal vascular caliber and blood flow in CADASIL. Methods Scanning laser Doppler flowmetry was used in a case control study (11 patients and controls) of peripapillary retinal circulat ion. Automated full field perfusion image analysis was used to analyze the flow data. Retinal vessel calibers were measured from retinal images acquired with s canning laser ophthalmoscopy. The caliber of the superior and inferior temporal retinal artery and vein were measured 1 and 2 mm from the disc rim, and the mean values were used for analysis. Results Retinal capillary peak systolic flow (m ean, 249 versus 311 arbitrary unit [AU] ; P=0.072) was lower, and mean capill ar y flow (mean, 184 versus 224 AU; P=0.12) and minimum diastolic flow (mean, 105 v ersus 132 AU; P=0.16) tended to be lower in patients than in controls. No signif icant difference in the calibers of proximal retinal arteries (mean, 104 versus1 08 μm) and veins (mean, 150 versus 145 μm) was found between the patients and controls. Conclusions Retinal capillary blood flow is mild to moderately reduced in CADASIL but that does not appear to cause major ischemic injury. Such reduct ion is analogous to that in the cerebral cortex in CADASIL patients with which r etina appears to share its relative sparing from severe arterial ischemic tissue damage. Background and Purpose Cerebral autosomal dominant arteriopathy with subcorti cal infarcts and leukoencephalopathy (CADASIL) is a progressive systemic nonathe rosclerotic angiopathy which causes ischemic strokes and vascular subcortical de mentia. A cross sec tional study was performed to examine the retinal vascular caliber and blood flow in CADASIL. Methods Scanning laser Doppler flowmetry was used in a case control study (11 patients and controls) of peripapillary retinal circulat ion. Automated full field perfusion image analysis was used to analyze the flow data. Retinal vessel calibers were measured from retinal images acquired with The caliber of the superior and inferior temporal retinal artery and vein were measured 1 and 2 mm from the disc rim, and the mean values ​​were used for analysis. Results Retinal capillary peak systolic flow (m ean, 249 versus 311 arbitrary unit [AU]; P ​​= 0.072) was lower, and the mean capill ar y flow (mean, 184 versus 224 A No sign of icant difference in the calibers of proximal retinal arteries (mean, 104 versus 1808; mean P = 0.12) and minimum diastolic flow (mean, 105 v ersus 132 AU; P = 0.16) tended to be lower in patients than in controls. μm) and veins (mean, 150 versus 145 μm) was found between the patients and controls. Conclusions Retinal capillary blood flow is mild to moderately reduced in CADASIL but that does not appear to cause major ischemic injury. in the cerebral cortex in CADASIL patients with which r etina appears to share its relative sparing from severe arterial ischemic tissue damage.