Objective.-To assess whether migraine is associated with retinal microvascular caliber.Background.-Migraine is believed to be associated with vascular disease,but few studies have investigated the relationship between structural microvascular changes and migraine.Design.-Population-based cross-sectional study.Methods.-Participants in the Blue Mountains Eye Study follow-up(1997 to 1999,n=2335,aged 54+)had retinal photographs taken.A computer-assisted method was used to measure average retinal arteriolar and venular diameters and calculate the arteriole-to-venule ratio.History of migraine was recorded by interview using International Headache Society criteria(1988).Results.-Subjects giving a history of migraine without aura(n=128)had narrower retinal arterioles than subjects giving a history of migraine with aura(n=182)or subjects with no migraine history(n=1619).After multivariate adjustment,mean retinal arteriolar diameter was 4.3 μ m(95% confidence interval 0.5,8.1)narrower in subjects reporting migraine without aura as compared to subjects with no migraine.Conclusions.Individuals with a history of migraine without aura were more likely to have slightly narrower retinal arteriolar caliber than individuals without migraine.This relationship was not present for migraine with aura.These data support the hypothesis that microvascular disease may be associated with certain types of migraine. Objective-To assess whether migraine is associated with retinal microvascular caliber. Background-migraine is believed to be associated with vascular disease, but few studies have investigated the relationship between structural microvascular changes and migraine. Design-Population-based cross-sectional study.Methods.-Participants in the Blue Mountains Eye Study follow-up (1997 to 1999, n = 2335, aged 54+) had retinal photographs taken. A computer-assisted method was used to measure average retinal arteriolar and venular diameters and calculate the arteriole-to-venule ratio. History of migraine was recorded by interview using International Headache Society criteria (1988). Results - Subjects giving a history of migraine without aura (n = 128) had narrower retinal arterioles than subjects giving a history of migraine with aura (n = 182) or subjects with no migraine history (n = 1619). After multivariate adjustment, mean retinal arteriolar diameter was 4.3 μm (95% confidence interval 0.5,8.1) narrower in subjec ts reporting migraine without aura as compared to subjects with no migraine.Conclusions.Individuals with a history of migraine without aura were more likely to have slightly narrower retinal arteriolar caliber than individuals without migraine.This relationship was not present for migraine with aura.These data support the hypothesis that microvascular disease may be associated with certain types of migraine.